diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/Kconfig | 30 | ||||
| -rw-r--r-- | kernel/rcu/rcu.h | 25 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 17 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 17 | ||||
| -rw-r--r-- | kernel/rcu/rcuperf.c | 27 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 434 | ||||
| -rw-r--r-- | kernel/rcu/srcutiny.c | 137 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 557 | ||||
| -rw-r--r-- | kernel/rcu/sync.c | 40 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 19 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 373 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 71 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 211 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 319 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 28 |
15 files changed, 1127 insertions, 1178 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index 939a2056c87a..37301430970e 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -87,36 +87,6 @@ config RCU_STALL_COMMON config RCU_NEED_SEGCBLIST def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU ) -config CONTEXT_TRACKING - bool - -config CONTEXT_TRACKING_FORCE - bool "Force context tracking" - depends on CONTEXT_TRACKING - default y if !NO_HZ_FULL - help - The major pre-requirement for full dynticks to work is to - support the context tracking subsystem. But there are also - other dependencies to provide in order to make the full - dynticks working. - - This option stands for testing when an arch implements the - context tracking backend but doesn't yet fullfill all the - requirements to make the full dynticks feature working. - Without the full dynticks, there is no way to test the support - for context tracking and the subsystems that rely on it: RCU - userspace extended quiescent state and tickless cputime - accounting. This option copes with the absence of the full - dynticks subsystem by forcing the context tracking on all - CPUs in the system. - - Say Y only if you're working on the development of an - architecture backend for the context tracking. - - Say N otherwise, this option brings an overhead that you - don't want in production. - - config RCU_FANOUT int "Tree-based hierarchical RCU fanout value" range 2 64 if 64BIT diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 2866166863f0..acee72c0b24b 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -1,23 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update definitions shared among RCU implementations. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2011 * - * Author: Paul E. McKenney <[email protected]> + * Author: Paul E. McKenney <[email protected]> */ #ifndef __LINUX_RCU_H @@ -30,7 +17,7 @@ #define RCU_TRACE(stmt) #endif /* #else #ifdef CONFIG_RCU_TRACE */ -/* Offset to allow for unmatched rcu_irq_{enter,exit}(). */ +/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */ #define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1) @@ -462,8 +449,6 @@ void rcu_request_urgent_qs_task(struct task_struct *t); enum rcutorture_type { RCU_FLAVOR, - RCU_BH_FLAVOR, - RCU_SCHED_FLAVOR, RCU_TASKS_FLAVOR, SRCU_FLAVOR, INVALID_RCU_FLAVOR @@ -526,12 +511,14 @@ srcu_batches_completed(struct srcu_struct *sp) { return 0; } static inline void rcu_force_quiescent_state(void) { } static inline void show_rcu_gp_kthreads(void) { } static inline int rcu_get_gp_kthreads_prio(void) { return 0; } +static inline void rcu_fwd_progress_check(unsigned long j) { } #else /* #ifdef CONFIG_TINY_RCU */ unsigned long rcu_get_gp_seq(void); unsigned long rcu_exp_batches_completed(void); unsigned long srcu_batches_completed(struct srcu_struct *sp); void show_rcu_gp_kthreads(void); int rcu_get_gp_kthreads_prio(void); +void rcu_fwd_progress_check(unsigned long j); void rcu_force_quiescent_state(void); extern struct workqueue_struct *rcu_gp_wq; extern struct workqueue_struct *rcu_par_gp_wq; @@ -539,8 +526,10 @@ extern struct workqueue_struct *rcu_par_gp_wq; #ifdef CONFIG_RCU_NOCB_CPU bool rcu_is_nocb_cpu(int cpu); +void rcu_bind_current_to_nocb(void); #else static inline bool rcu_is_nocb_cpu(int cpu) { return false; } +static inline void rcu_bind_current_to_nocb(void) { } #endif #endif /* __LINUX_RCU_H */ diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 5aff271adf1e..9bd5f6023c21 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * RCU segmented callback lists, function definitions * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2017 * - * Authors: Paul E. McKenney <[email protected]> + * Authors: Paul E. McKenney <[email protected]> */ #include <linux/types.h> diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index 948470cef385..71b64648464e 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -1,23 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * RCU segmented callback lists, internal-to-rcu header file * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2017 * - * Authors: Paul E. McKenney <[email protected]> + * Authors: Paul E. McKenney <[email protected]> */ #include <linux/rcu_segcblist.h> diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index b459da70b4fc..c29761152874 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update module-based performance-test facility * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2015 * - * Authors: Paul E. McKenney <[email protected]> + * Authors: Paul E. McKenney <[email protected]> */ #define pr_fmt(fmt) fmt @@ -54,7 +41,7 @@ #include "rcu.h" MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Paul E. McKenney <[email protected]>"); +MODULE_AUTHOR("Paul E. McKenney <[email protected]>"); #define PERF_FLAG "-perf:" #define PERFOUT_STRING(s) \ @@ -83,13 +70,19 @@ MODULE_AUTHOR("Paul E. McKenney <[email protected]>"); * Various other use cases may of course be specified. */ +#ifdef MODULE +# define RCUPERF_SHUTDOWN 0 +#else +# define RCUPERF_SHUTDOWN 1 +#endif + torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives"); torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader"); torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); torture_param(int, holdoff, 10, "Holdoff time before test start (s)"); torture_param(int, nreaders, -1, "Number of RCU reader threads"); torture_param(int, nwriters, -1, "Number of RCU updater threads"); -torture_param(bool, shutdown, !IS_ENABLED(MODULE), +torture_param(bool, shutdown, RCUPERF_SHUTDOWN, "Shutdown at end of performance tests."); torture_param(int, verbose, 1, "Enable verbose debugging printk()s"); torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable"); diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 210c77460365..f14d1b18a74f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update module-based torture test facility * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2005, 2006 * - * Authors: Paul E. McKenney <[email protected]> + * Authors: Paul E. McKenney <[email protected]> * Josh Triplett <[email protected]> * * See also: Documentation/RCU/torture.txt @@ -56,11 +43,12 @@ #include <linux/vmalloc.h> #include <linux/sched/debug.h> #include <linux/sched/sysctl.h> +#include <linux/oom.h> #include "rcu.h" MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Paul E. McKenney <[email protected]> and Josh Triplett <[email protected]>"); +MODULE_AUTHOR("Paul E. McKenney <[email protected]> and Josh Triplett <[email protected]>"); /* Bits for ->extendables field, extendables param, and related definitions. */ @@ -80,13 +68,6 @@ MODULE_AUTHOR("Paul E. McKenney <[email protected]> and Josh Triplett <josh@jos /* Must be power of two minus one. */ #define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3) -torture_param(int, cbflood_inter_holdoff, HZ, - "Holdoff between floods (jiffies)"); -torture_param(int, cbflood_intra_holdoff, 1, - "Holdoff between bursts (jiffies)"); -torture_param(int, cbflood_n_burst, 3, "# bursts in flood, zero to disable"); -torture_param(int, cbflood_n_per_burst, 20000, - "# callbacks per burst in flood"); torture_param(int, extendables, RCUTORTURE_MAX_EXTEND, "Extend readers by disabling bh (1), irqs (2), or preempt (4)"); torture_param(int, fqs_duration, 0, @@ -138,12 +119,10 @@ module_param(torture_type, charp, 0444); MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)"); static int nrealreaders; -static int ncbflooders; static struct task_struct *writer_task; static struct task_struct **fakewriter_tasks; static struct task_struct **reader_tasks; static struct task_struct *stats_task; -static struct task_struct **cbflood_task; static struct task_struct *fqs_task; static struct task_struct *boost_tasks[NR_CPUS]; static struct task_struct *stall_task; @@ -181,7 +160,6 @@ static long n_rcu_torture_boosts; static atomic_long_t n_rcu_torture_timers; static long n_barrier_attempts; static long n_barrier_successes; /* did rcu_barrier test succeed? */ -static atomic_long_t n_cbfloods; static struct list_head rcu_torture_removed; static int rcu_torture_writer_state; @@ -259,6 +237,8 @@ static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */ static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */ static DECLARE_WAIT_QUEUE_HEAD(barrier_wq); +static bool rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */ + /* * Allocate an element from the rcu_tortures pool. */ @@ -348,7 +328,8 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) * period, and we want a long delay occasionally to trigger * force_quiescent_state. */ - if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { + if (!rcu_fwd_cb_nodelay && + !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { started = cur_ops->get_gp_seq(); ts = rcu_trace_clock_local(); if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK)) @@ -870,59 +851,6 @@ checkwait: stutter_wait("rcu_torture_boost"); return 0; } -static void rcu_torture_cbflood_cb(struct rcu_head *rhp) -{ -} - -/* - * RCU torture callback-flood kthread. Repeatedly induces bursts of calls - * to call_rcu() or analogous, increasing the probability of occurrence - * of callback-overflow corner cases. - */ -static int -rcu_torture_cbflood(void *arg) -{ - int err = 1; - int i; - int j; - struct rcu_head *rhp; - - if (cbflood_n_per_burst > 0 && - cbflood_inter_holdoff > 0 && - cbflood_intra_holdoff > 0 && - cur_ops->call && - cur_ops->cb_barrier) { - rhp = vmalloc(array3_size(cbflood_n_burst, - cbflood_n_per_burst, - sizeof(*rhp))); - err = !rhp; - } - if (err) { - VERBOSE_TOROUT_STRING("rcu_torture_cbflood disabled: Bad args or OOM"); - goto wait_for_stop; - } - VERBOSE_TOROUT_STRING("rcu_torture_cbflood task started"); - do { - schedule_timeout_interruptible(cbflood_inter_holdoff); - atomic_long_inc(&n_cbfloods); - WARN_ON(signal_pending(current)); - for (i = 0; i < cbflood_n_burst; i++) { - for (j = 0; j < cbflood_n_per_burst; j++) { - cur_ops->call(&rhp[i * cbflood_n_per_burst + j], - rcu_torture_cbflood_cb); - } - schedule_timeout_interruptible(cbflood_intra_holdoff); - WARN_ON(signal_pending(current)); - } - cur_ops->cb_barrier(); - stutter_wait("rcu_torture_cbflood"); - } while (!torture_must_stop()); - vfree(rhp); -wait_for_stop: - torture_kthread_stopping("rcu_torture_cbflood"); - return 0; -} - /* * RCU torture force-quiescent-state kthread. Repeatedly induces * bursts of calls to force_quiescent_state(), increasing the probability @@ -1457,11 +1385,10 @@ rcu_torture_stats_print(void) n_rcu_torture_boosts, atomic_long_read(&n_rcu_torture_timers)); torture_onoff_stats(); - pr_cont("barrier: %ld/%ld:%ld ", + pr_cont("barrier: %ld/%ld:%ld\n", n_barrier_successes, n_barrier_attempts, n_rcu_torture_barrier_error); - pr_cont("cbflood: %ld\n", atomic_long_read(&n_cbfloods)); pr_alert("%s%s ", torture_type, TORTURE_FLAG); if (atomic_read(&n_rcu_torture_mberror) != 0 || @@ -1674,8 +1601,104 @@ static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp) cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb); } -/* Carry out grace-period forward-progress testing. */ -static int rcu_torture_fwd_prog(void *args) +/* State for continuous-flood RCU callbacks. */ +struct rcu_fwd_cb { + struct rcu_head rh; + struct rcu_fwd_cb *rfc_next; + int rfc_gps; +}; +static DEFINE_SPINLOCK(rcu_fwd_lock); +static struct rcu_fwd_cb *rcu_fwd_cb_head; +static struct rcu_fwd_cb **rcu_fwd_cb_tail = &rcu_fwd_cb_head; +static long n_launders_cb; +static unsigned long rcu_fwd_startat; +static bool rcu_fwd_emergency_stop; +#define MAX_FWD_CB_JIFFIES (8 * HZ) /* Maximum CB test duration. */ +#define MIN_FWD_CB_LAUNDERS 3 /* This many CB invocations to count. */ +#define MIN_FWD_CBS_LAUNDERED 100 /* Number of counted CBs. */ +#define FWD_CBS_HIST_DIV 10 /* Histogram buckets/second. */ +struct rcu_launder_hist { + long n_launders; + unsigned long launder_gp_seq; +}; +#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV)) +static struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST]; +static unsigned long rcu_launder_gp_seq_start; + +static void rcu_torture_fwd_cb_hist(void) +{ + unsigned long gps; + unsigned long gps_old; + int i; + int j; + + for (i = ARRAY_SIZE(n_launders_hist) - 1; i > 0; i--) + if (n_launders_hist[i].n_launders > 0) + break; + pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):", + __func__, jiffies - rcu_fwd_startat); + gps_old = rcu_launder_gp_seq_start; + for (j = 0; j <= i; j++) { + gps = n_launders_hist[j].launder_gp_seq; + pr_cont(" %ds/%d: %ld:%ld", + j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j].n_launders, + rcutorture_seq_diff(gps, gps_old)); + gps_old = gps; + } + pr_cont("\n"); +} + +/* Callback function for continuous-flood RCU callbacks. */ +static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) +{ + unsigned long flags; + int i; + struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh); + struct rcu_fwd_cb **rfcpp; + + rfcp->rfc_next = NULL; + rfcp->rfc_gps++; + spin_lock_irqsave(&rcu_fwd_lock, flags); + rfcpp = rcu_fwd_cb_tail; + rcu_fwd_cb_tail = &rfcp->rfc_next; + WRITE_ONCE(*rfcpp, rfcp); + WRITE_ONCE(n_launders_cb, n_launders_cb + 1); + i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); + if (i >= ARRAY_SIZE(n_launders_hist)) + i = ARRAY_SIZE(n_launders_hist) - 1; + n_launders_hist[i].n_launders++; + n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq(); + spin_unlock_irqrestore(&rcu_fwd_lock, flags); +} + +/* + * Free all callbacks on the rcu_fwd_cb_head list, either because the + * test is over or because we hit an OOM event. + */ +static unsigned long rcu_torture_fwd_prog_cbfree(void) +{ + unsigned long flags; + unsigned long freed = 0; + struct rcu_fwd_cb *rfcp; + + for (;;) { + spin_lock_irqsave(&rcu_fwd_lock, flags); + rfcp = rcu_fwd_cb_head; + if (!rfcp) + break; + rcu_fwd_cb_head = rfcp->rfc_next; + if (!rcu_fwd_cb_head) + rcu_fwd_cb_tail = &rcu_fwd_cb_head; + spin_unlock_irqrestore(&rcu_fwd_lock, flags); + kfree(rfcp); + freed++; + } + spin_unlock_irqrestore(&rcu_fwd_lock, flags); + return freed; +} + +/* Carry out need_resched()/cond_resched() forward-progress testing. */ +static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) { unsigned long cver; unsigned long dur; @@ -1686,56 +1709,187 @@ static int rcu_torture_fwd_prog(void *args) int sd4; bool selfpropcb = false; unsigned long stopat; - int tested = 0; - int tested_tries = 0; static DEFINE_TORTURE_RANDOM(trs); - VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started"); - if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST)) - set_user_nice(current, MAX_NICE); if (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) { init_rcu_head_on_stack(&fcs.rh); selfpropcb = true; } + + /* Tight loop containing cond_resched(). */ + if (selfpropcb) { + WRITE_ONCE(fcs.stop, 0); + cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb); + } + cver = READ_ONCE(rcu_torture_current_version); + gps = cur_ops->get_gp_seq(); + sd = cur_ops->stall_dur() + 1; + sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div; + dur = sd4 + torture_random(&trs) % (sd - sd4); + WRITE_ONCE(rcu_fwd_startat, jiffies); + stopat = rcu_fwd_startat + dur; + while (time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { + idx = cur_ops->readlock(); + udelay(10); + cur_ops->readunlock(idx); + if (!fwd_progress_need_resched || need_resched()) + cond_resched(); + } + (*tested_tries)++; + if (!time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { + (*tested)++; + cver = READ_ONCE(rcu_torture_current_version) - cver; + gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps); + WARN_ON(!cver && gps < 2); + pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps); + } + if (selfpropcb) { + WRITE_ONCE(fcs.stop, 1); + cur_ops->sync(); /* Wait for running CB to complete. */ + cur_ops->cb_barrier(); /* Wait for queued callbacks. */ + } + + if (selfpropcb) { + WARN_ON(READ_ONCE(fcs.stop) != 2); + destroy_rcu_head_on_stack(&fcs.rh); + } +} + +/* Carry out call_rcu() forward-progress testing. */ +static void rcu_torture_fwd_prog_cr(void) +{ + unsigned long cver; + unsigned long gps; + int i; + long n_launders; + long n_launders_cb_snap; + long n_launders_sa; + long n_max_cbs; + long n_max_gps; + struct rcu_fwd_cb *rfcp; + struct rcu_fwd_cb *rfcpn; + unsigned long stopat; + unsigned long stoppedat; + + if (READ_ONCE(rcu_fwd_emergency_stop)) + return; /* Get out of the way quickly, no GP wait! */ + + /* Loop continuously posting RCU callbacks. */ + WRITE_ONCE(rcu_fwd_cb_nodelay, true); + cur_ops->sync(); /* Later readers see above write. */ + WRITE_ONCE(rcu_fwd_startat, jiffies); + stopat = rcu_fwd_startat + MAX_FWD_CB_JIFFIES; + n_launders = 0; + n_launders_cb = 0; + n_launders_sa = 0; + n_max_cbs = 0; + n_max_gps = 0; + for (i = 0; i < ARRAY_SIZE(n_launders_hist); i++) + n_launders_hist[i].n_launders = 0; + cver = READ_ONCE(rcu_torture_current_version); + gps = cur_ops->get_gp_seq(); + rcu_launder_gp_seq_start = gps; + while (time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { + rfcp = READ_ONCE(rcu_fwd_cb_head); + rfcpn = NULL; + if (rfcp) + rfcpn = READ_ONCE(rfcp->rfc_next); + if (rfcpn) { + if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS && + ++n_max_gps >= MIN_FWD_CBS_LAUNDERED) + break; + rcu_fwd_cb_head = rfcpn; + n_launders++; + n_launders_sa++; + } else { + rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL); + if (WARN_ON_ONCE(!rfcp)) { + schedule_timeout_interruptible(1); + continue; + } + n_max_cbs++; + n_launders_sa = 0; + rfcp->rfc_gps = 0; + } + cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr); + cond_resched(); + } + stoppedat = jiffies; + n_launders_cb_snap = READ_ONCE(n_launders_cb); + cver = READ_ONCE(rcu_torture_current_version) - cver; + gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps); + cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */ + (void)rcu_torture_fwd_prog_cbfree(); + + WRITE_ONCE(rcu_fwd_cb_nodelay, false); + if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) { + WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED); + pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n", + __func__, + stoppedat - rcu_fwd_startat, jiffies - stoppedat, + n_launders + n_max_cbs - n_launders_cb_snap, + n_launders, n_launders_sa, + n_max_gps, n_max_cbs, cver, gps); + rcu_torture_fwd_cb_hist(); + } +} + + +/* + * OOM notifier, but this only prints diagnostic information for the + * current forward-progress test. + */ +static int rcutorture_oom_notify(struct notifier_block *self, + unsigned long notused, void *nfreed) +{ + WARN(1, "%s invoked upon OOM during forward-progress testing.\n", + __func__); + rcu_torture_fwd_cb_hist(); + rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat) / 2)); + WRITE_ONCE(rcu_fwd_emergency_stop, true); + smp_mb(); /* Emergency stop before free and wait to avoid hangs. */ + pr_info("%s: Freed %lu RCU callbacks.\n", + __func__, rcu_torture_fwd_prog_cbfree()); + rcu_barrier(); + pr_info("%s: Freed %lu RCU callbacks.\n", + __func__, rcu_torture_fwd_prog_cbfree()); + rcu_barrier(); + pr_info("%s: Freed %lu RCU callbacks.\n", + __func__, rcu_torture_fwd_prog_cbfree()); + smp_mb(); /* Frees before return to avoid redoing OOM. */ + (*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */ + pr_info("%s returning after OOM processing.\n", __func__); + return NOTIFY_OK; +} + +static struct notifier_block rcutorture_oom_nb = { + .notifier_call = rcutorture_oom_notify +}; + +/* Carry out grace-period forward-progress testing. */ +static int rcu_torture_fwd_prog(void *args) +{ + int tested = 0; + int tested_tries = 0; + + VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started"); + rcu_bind_current_to_nocb(); + if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST)) + set_user_nice(current, MAX_NICE); do { schedule_timeout_interruptible(fwd_progress_holdoff * HZ); - if (selfpropcb) { - WRITE_ONCE(fcs.stop, 0); - cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb); - } - cver = READ_ONCE(rcu_torture_current_version); - gps = cur_ops->get_gp_seq(); - sd = cur_ops->stall_dur() + 1; - sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div; - dur = sd4 + torture_random(&trs) % (sd - sd4); - stopat = jiffies + dur; - while (time_before(jiffies, stopat) && !torture_must_stop()) { - idx = cur_ops->readlock(); - udelay(10); - cur_ops->readunlock(idx); - if (!fwd_progress_need_resched || need_resched()) - cond_resched(); - } - tested_tries++; - if (!time_before(jiffies, stopat) && !torture_must_stop()) { - tested++; - cver = READ_ONCE(rcu_torture_current_version) - cver; - gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps); - WARN_ON(!cver && gps < 2); - pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps); - } - if (selfpropcb) { - WRITE_ONCE(fcs.stop, 1); - cur_ops->sync(); /* Wait for running CB to complete. */ - cur_ops->cb_barrier(); /* Wait for queued callbacks. */ - } + WRITE_ONCE(rcu_fwd_emergency_stop, false); + register_oom_notifier(&rcutorture_oom_nb); + rcu_torture_fwd_prog_nr(&tested, &tested_tries); + rcu_torture_fwd_prog_cr(); + unregister_oom_notifier(&rcutorture_oom_nb); + /* Avoid slow periods, better to test when busy. */ stutter_wait("rcu_torture_fwd_prog"); } while (!torture_must_stop()); - if (selfpropcb) { - WARN_ON(READ_ONCE(fcs.stop) != 2); - destroy_rcu_head_on_stack(&fcs.rh); - } /* Short runs might not contain a valid forward-progress attempt. */ WARN_ON(!tested && tested_tries >= 5); pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries); @@ -1748,7 +1902,8 @@ static int __init rcu_torture_fwd_prog_init(void) { if (!fwd_progress) return 0; /* Not requested, so don't do it. */ - if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0) { + if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 || + cur_ops == &rcu_busted_ops) { VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test"); return 0; } @@ -1968,8 +2123,6 @@ rcu_torture_cleanup(void) cur_ops->name, gp_seq, flags); torture_stop_kthread(rcu_torture_stats, stats_task); torture_stop_kthread(rcu_torture_fqs, fqs_task); - for (i = 0; i < ncbflooders; i++) - torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]); if (rcu_torture_can_boost()) cpuhp_remove_state(rcutor_hp); @@ -2077,6 +2230,14 @@ static void rcu_test_debug_objects(void) #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ } +static void rcutorture_sync(void) +{ + static unsigned long n; + + if (cur_ops->sync && !(++n & 0xfff)) + cur_ops->sync(); +} + static int __init rcu_torture_init(void) { @@ -2238,7 +2399,8 @@ rcu_torture_init(void) firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup); if (firsterr) goto unwind; - firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval); + firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, + rcutorture_sync); if (firsterr) goto unwind; firsterr = rcu_torture_stall_init(); @@ -2252,24 +2414,6 @@ rcu_torture_init(void) goto unwind; if (object_debug) rcu_test_debug_objects(); - if (cbflood_n_burst > 0) { - /* Create the cbflood threads */ - ncbflooders = (num_online_cpus() + 3) / 4; - cbflood_task = kcalloc(ncbflooders, sizeof(*cbflood_task), - GFP_KERNEL); - if (!cbflood_task) { - VERBOSE_TOROUT_ERRSTRING("out of memory"); - firsterr = -ENOMEM; - goto unwind; - } - for (i = 0; i < ncbflooders; i++) { - firsterr = torture_create_kthread(rcu_torture_cbflood, - NULL, - cbflood_task[i]); - if (firsterr) - goto unwind; - } - } torture_init_end(); return 0; diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index b46e6683f8c9..5d4a39a6505a 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -1,24 +1,11 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Sleepable Read-Copy Update mechanism for mutual exclusion, * tiny version for non-preemptible single-CPU use. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2017 * - * Author: Paul McKenney <[email protected]> + * Author: Paul McKenney <[email protected]> */ #include <linux/export.h> @@ -37,30 +24,30 @@ int rcu_scheduler_active __read_mostly; static LIST_HEAD(srcu_boot_list); static bool srcu_init_done; -static int init_srcu_struct_fields(struct srcu_struct *sp) +static int init_srcu_struct_fields(struct srcu_struct *ssp) { - sp->srcu_lock_nesting[0] = 0; - sp->srcu_lock_nesting[1] = 0; - init_swait_queue_head(&sp->srcu_wq); - sp->srcu_cb_head = NULL; - sp->srcu_cb_tail = &sp->srcu_cb_head; - sp->srcu_gp_running = false; - sp->srcu_gp_waiting = false; - sp->srcu_idx = 0; - INIT_WORK(&sp->srcu_work, srcu_drive_gp); - INIT_LIST_HEAD(&sp->srcu_work.entry); + ssp->srcu_lock_nesting[0] = 0; + ssp->srcu_lock_nesting[1] = 0; + init_swait_queue_head(&ssp->srcu_wq); + ssp->srcu_cb_head = NULL; + ssp->srcu_cb_tail = &ssp->srcu_cb_head; + ssp->srcu_gp_running = false; + ssp->srcu_gp_waiting = false; + ssp->srcu_idx = 0; + INIT_WORK(&ssp->srcu_work, srcu_drive_gp); + INIT_LIST_HEAD(&ssp->srcu_work.entry); return 0; } #ifdef CONFIG_DEBUG_LOCK_ALLOC -int __init_srcu_struct(struct srcu_struct *sp, const char *name, +int __init_srcu_struct(struct srcu_struct *ssp, const char *name, struct lock_class_key *key) { /* Don't re-initialize a lock while it is held. */ - debug_check_no_locks_freed((void *)sp, sizeof(*sp)); - lockdep_init_map(&sp->dep_map, name, key, 0); - return init_srcu_struct_fields(sp); + debug_check_no_locks_freed((void *)ssp, sizeof(*ssp)); + lockdep_init_map(&ssp->dep_map, name, key, 0); + return init_srcu_struct_fields(ssp); } EXPORT_SYMBOL_GPL(__init_srcu_struct); @@ -68,15 +55,15 @@ EXPORT_SYMBOL_GPL(__init_srcu_struct); /* * init_srcu_struct - initialize a sleep-RCU structure - * @sp: structure to initialize. + * @ssp: structure to initialize. * * Must invoke this on a given srcu_struct before passing that srcu_struct * to any other function. Each srcu_struct represents a separate domain * of SRCU protection. */ -int init_srcu_struct(struct srcu_struct *sp) +int init_srcu_struct(struct srcu_struct *ssp) { - return init_srcu_struct_fields(sp); + return init_srcu_struct_fields(ssp); } EXPORT_SYMBOL_GPL(init_srcu_struct); @@ -84,22 +71,22 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); /* * cleanup_srcu_struct - deconstruct a sleep-RCU structure - * @sp: structure to clean up. + * @ssp: structure to clean up. * * Must invoke this after you are finished using a given srcu_struct that * was initialized via init_srcu_struct(), else you leak memory. */ -void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) +void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced) { - WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]); + WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]); if (quiesced) - WARN_ON(work_pending(&sp->srcu_work)); + WARN_ON(work_pending(&ssp->srcu_work)); else - flush_work(&sp->srcu_work); - WARN_ON(sp->srcu_gp_running); - WARN_ON(sp->srcu_gp_waiting); - WARN_ON(sp->srcu_cb_head); - WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail); + flush_work(&ssp->srcu_work); + WARN_ON(ssp->srcu_gp_running); + WARN_ON(ssp->srcu_gp_waiting); + WARN_ON(ssp->srcu_cb_head); + WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail); } EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); @@ -107,13 +94,13 @@ EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); * Removes the count for the old reader from the appropriate element of * the srcu_struct. */ -void __srcu_read_unlock(struct srcu_struct *sp, int idx) +void __srcu_read_unlock(struct srcu_struct *ssp, int idx) { - int newval = sp->srcu_lock_nesting[idx] - 1; + int newval = ssp->srcu_lock_nesting[idx] - 1; - WRITE_ONCE(sp->srcu_lock_nesting[idx], newval); - if (!newval && READ_ONCE(sp->srcu_gp_waiting)) - swake_up_one(&sp->srcu_wq); + WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval); + if (!newval && READ_ONCE(ssp->srcu_gp_waiting)) + swake_up_one(&ssp->srcu_wq); } EXPORT_SYMBOL_GPL(__srcu_read_unlock); @@ -127,24 +114,24 @@ void srcu_drive_gp(struct work_struct *wp) int idx; struct rcu_head *lh; struct rcu_head *rhp; - struct srcu_struct *sp; + struct srcu_struct *ssp; - sp = container_of(wp, struct srcu_struct, srcu_work); - if (sp->srcu_gp_running || !READ_ONCE(sp->srcu_cb_head)) + ssp = container_of(wp, struct srcu_struct, srcu_work); + if (ssp->srcu_gp_running || !READ_ONCE(ssp->srcu_cb_head)) return; /* Already running or nothing to do. */ /* Remove recently arrived callbacks and wait for readers. */ - WRITE_ONCE(sp->srcu_gp_running, true); + WRITE_ONCE(ssp->srcu_gp_running, true); local_irq_disable(); - lh = sp->srcu_cb_head; - sp->srcu_cb_head = NULL; - sp->srcu_cb_tail = &sp->srcu_cb_head; + lh = ssp->srcu_cb_head; + ssp->srcu_cb_head = NULL; + ssp->srcu_cb_tail = &ssp->srcu_cb_head; local_irq_enable(); - idx = sp->srcu_idx; - WRITE_ONCE(sp->srcu_idx, !sp->srcu_idx); - WRITE_ONCE(sp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */ - swait_event_exclusive(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx])); - WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ + idx = ssp->srcu_idx; + WRITE_ONCE(ssp->srcu_idx, !ssp->srcu_idx); + WRITE_ONCE(ssp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */ + swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx])); + WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ /* Invoke the callbacks we removed above. */ while (lh) { @@ -161,9 +148,9 @@ void srcu_drive_gp(struct work_struct *wp) * at interrupt level, but the ->srcu_gp_running checks will * straighten that out. */ - WRITE_ONCE(sp->srcu_gp_running, false); - if (READ_ONCE(sp->srcu_cb_head)) - schedule_work(&sp->srcu_work); + WRITE_ONCE(ssp->srcu_gp_running, false); + if (READ_ONCE(ssp->srcu_cb_head)) + schedule_work(&ssp->srcu_work); } EXPORT_SYMBOL_GPL(srcu_drive_gp); @@ -171,7 +158,7 @@ EXPORT_SYMBOL_GPL(srcu_drive_gp); * Enqueue an SRCU callback on the specified srcu_struct structure, * initiating grace-period processing if it is not already running. */ -void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, +void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, rcu_callback_t func) { unsigned long flags; @@ -179,14 +166,14 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, rhp->func = func; rhp->next = NULL; local_irq_save(flags); - *sp->srcu_cb_tail = rhp; - sp->srcu_cb_tail = &rhp->next; + *ssp->srcu_cb_tail = rhp; + ssp->srcu_cb_tail = &rhp->next; local_irq_restore(flags); - if (!READ_ONCE(sp->srcu_gp_running)) { + if (!READ_ONCE(ssp->srcu_gp_running)) { if (likely(srcu_init_done)) - schedule_work(&sp->srcu_work); - else if (list_empty(&sp->srcu_work.entry)) - list_add(&sp->srcu_work.entry, &srcu_boot_list); + schedule_work(&ssp->srcu_work); + else if (list_empty(&ssp->srcu_work.entry)) + list_add(&ssp->srcu_work.entry, &srcu_boot_list); } } EXPORT_SYMBOL_GPL(call_srcu); @@ -194,13 +181,13 @@ EXPORT_SYMBOL_GPL(call_srcu); /* * synchronize_srcu - wait for prior SRCU read-side critical-section completion */ -void synchronize_srcu(struct srcu_struct *sp) +void synchronize_srcu(struct srcu_struct *ssp) { struct rcu_synchronize rs; init_rcu_head_on_stack(&rs.head); init_completion(&rs.completion); - call_srcu(sp, &rs.head, wakeme_after_rcu); + call_srcu(ssp, &rs.head, wakeme_after_rcu); wait_for_completion(&rs.completion); destroy_rcu_head_on_stack(&rs.head); } @@ -219,13 +206,13 @@ void __init rcu_scheduler_starting(void) */ void __init srcu_init(void) { - struct srcu_struct *sp; + struct srcu_struct *ssp; srcu_init_done = true; while (!list_empty(&srcu_boot_list)) { - sp = list_first_entry(&srcu_boot_list, + ssp = list_first_entry(&srcu_boot_list, struct srcu_struct, srcu_work.entry); - list_del_init(&sp->srcu_work.entry); - schedule_work(&sp->srcu_work); + list_del_init(&ssp->srcu_work.entry); + schedule_work(&ssp->srcu_work); } } diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index a8846ed7f352..a60b8ba9e1ac 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1,24 +1,11 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Sleepable Read-Copy Update mechanism for mutual exclusion. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2006 * Copyright (C) Fujitsu, 2012 * - * Author: Paul McKenney <[email protected]> + * Author: Paul McKenney <[email protected]> * Lai Jiangshan <[email protected]> * * For detailed explanation of Read-Copy Update mechanism see - @@ -56,8 +43,9 @@ static LIST_HEAD(srcu_boot_list); static bool __read_mostly srcu_init_done; static void srcu_invoke_callbacks(struct work_struct *work); -static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); +static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay); static void process_srcu(struct work_struct *work); +static void srcu_delay_timer(struct timer_list *t); /* Wrappers for lock acquisition and release, see raw_spin_lock_rcu_node(). */ #define spin_lock_rcu_node(p) \ @@ -92,7 +80,7 @@ do { \ * srcu_read_unlock() running against them. So if the is_static parameter * is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[]. */ -static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) +static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static) { int cpu; int i; @@ -103,13 +91,13 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) struct srcu_node *snp_first; /* Work out the overall tree geometry. */ - sp->level[0] = &sp->node[0]; + ssp->level[0] = &ssp->node[0]; for (i = 1; i < rcu_num_lvls; i++) - sp->level[i] = sp->level[i - 1] + num_rcu_lvl[i - 1]; + ssp->level[i] = ssp->level[i - 1] + num_rcu_lvl[i - 1]; rcu_init_levelspread(levelspread, num_rcu_lvl); /* Each pass through this loop initializes one srcu_node structure. */ - srcu_for_each_node_breadth_first(sp, snp) { + srcu_for_each_node_breadth_first(ssp, snp) { spin_lock_init(&ACCESS_PRIVATE(snp, lock)); WARN_ON_ONCE(ARRAY_SIZE(snp->srcu_have_cbs) != ARRAY_SIZE(snp->srcu_data_have_cbs)); @@ -120,17 +108,17 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) snp->srcu_gp_seq_needed_exp = 0; snp->grplo = -1; snp->grphi = -1; - if (snp == &sp->node[0]) { + if (snp == &ssp->node[0]) { /* Root node, special case. */ snp->srcu_parent = NULL; continue; } /* Non-root node. */ - if (snp == sp->level[level + 1]) + if (snp == ssp->level[level + 1]) level++; - snp->srcu_parent = sp->level[level - 1] + - (snp - sp->level[level]) / + snp->srcu_parent = ssp->level[level - 1] + + (snp - ssp->level[level]) / levelspread[level - 1]; } @@ -141,14 +129,14 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) WARN_ON_ONCE(ARRAY_SIZE(sdp->srcu_lock_count) != ARRAY_SIZE(sdp->srcu_unlock_count)); level = rcu_num_lvls - 1; - snp_first = sp->level[level]; + snp_first = ssp->level[level]; for_each_possible_cpu(cpu) { - sdp = per_cpu_ptr(sp->sda, cpu); + sdp = per_cpu_ptr(ssp->sda, cpu); spin_lock_init(&ACCESS_PRIVATE(sdp, lock)); rcu_segcblist_init(&sdp->srcu_cblist); sdp->srcu_cblist_invoking = false; - sdp->srcu_gp_seq_needed = sp->srcu_gp_seq; - sdp->srcu_gp_seq_needed_exp = sp->srcu_gp_seq; + sdp->srcu_gp_seq_needed = ssp->srcu_gp_seq; + sdp->srcu_gp_seq_needed_exp = ssp->srcu_gp_seq; sdp->mynode = &snp_first[cpu / levelspread[level]]; for (snp = sdp->mynode; snp != NULL; snp = snp->srcu_parent) { if (snp->grplo < 0) @@ -156,8 +144,9 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) snp->grphi = cpu; } sdp->cpu = cpu; - INIT_DELAYED_WORK(&sdp->work, srcu_invoke_callbacks); - sdp->sp = sp; + INIT_WORK(&sdp->work, srcu_invoke_callbacks); + timer_setup(&sdp->delay_work, srcu_delay_timer, 0); + sdp->ssp = ssp; sdp->grpmask = 1 << (cpu - sdp->mynode->grplo); if (is_static) continue; @@ -176,35 +165,35 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) * parameter is passed through to init_srcu_struct_nodes(), and * also tells us that ->sda has already been wired up to srcu_data. */ -static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) +static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) { - mutex_init(&sp->srcu_cb_mutex); - mutex_init(&sp->srcu_gp_mutex); - sp->srcu_idx = 0; - sp->srcu_gp_seq = 0; - sp->srcu_barrier_seq = 0; - mutex_init(&sp->srcu_barrier_mutex); - atomic_set(&sp->srcu_barrier_cpu_cnt, 0); - INIT_DELAYED_WORK(&sp->work, process_srcu); + mutex_init(&ssp->srcu_cb_mutex); + mutex_init(&ssp->srcu_gp_mutex); + ssp->srcu_idx = 0; + ssp->srcu_gp_seq = 0; + ssp->srcu_barrier_seq = 0; + mutex_init(&ssp->srcu_barrier_mutex); + atomic_set(&ssp->srcu_barrier_cpu_cnt, 0); + INIT_DELAYED_WORK(&ssp->work, process_srcu); if (!is_static) - sp->sda = alloc_percpu(struct srcu_data); - init_srcu_struct_nodes(sp, is_static); - sp->srcu_gp_seq_needed_exp = 0; - sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); - smp_store_release(&sp->srcu_gp_seq_needed, 0); /* Init done. */ - return sp->sda ? 0 : -ENOMEM; + ssp->sda = alloc_percpu(struct srcu_data); + init_srcu_struct_nodes(ssp, is_static); + ssp->srcu_gp_seq_needed_exp = 0; + ssp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */ + return ssp->sda ? 0 : -ENOMEM; } #ifdef CONFIG_DEBUG_LOCK_ALLOC -int __init_srcu_struct(struct srcu_struct *sp, const char *name, +int __init_srcu_struct(struct srcu_struct *ssp, const char *name, struct lock_class_key *key) { /* Don't re-initialize a lock while it is held. */ - debug_check_no_locks_freed((void *)sp, sizeof(*sp)); - lockdep_init_map(&sp->dep_map, name, key, 0); - spin_lock_init(&ACCESS_PRIVATE(sp, lock)); - return init_srcu_struct_fields(sp, false); + debug_check_no_locks_freed((void *)ssp, sizeof(*ssp)); + lockdep_init_map(&ssp->dep_map, name, key, 0); + spin_lock_init(&ACCESS_PRIVATE(ssp, lock)); + return init_srcu_struct_fields(ssp, false); } EXPORT_SYMBOL_GPL(__init_srcu_struct); @@ -212,16 +201,16 @@ EXPORT_SYMBOL_GPL(__init_srcu_struct); /** * init_srcu_struct - initialize a sleep-RCU structure - * @sp: structure to initialize. + * @ssp: structure to initialize. * * Must invoke this on a given srcu_struct before passing that srcu_struct * to any other function. Each srcu_struct represents a separate domain * of SRCU protection. */ -int init_srcu_struct(struct srcu_struct *sp) +int init_srcu_struct(struct srcu_struct *ssp) { - spin_lock_init(&ACCESS_PRIVATE(sp, lock)); - return init_srcu_struct_fields(sp, false); + spin_lock_init(&ACCESS_PRIVATE(ssp, lock)); + return init_srcu_struct_fields(ssp, false); } EXPORT_SYMBOL_GPL(init_srcu_struct); @@ -231,37 +220,37 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); * First-use initialization of statically allocated srcu_struct * structure. Wiring up the combining tree is more than can be * done with compile-time initialization, so this check is added - * to each update-side SRCU primitive. Use sp->lock, which -is- + * to each update-side SRCU primitive. Use ssp->lock, which -is- * compile-time initialized, to resolve races involving multiple * CPUs trying to garner first-use privileges. */ -static void check_init_srcu_struct(struct srcu_struct *sp) +static void check_init_srcu_struct(struct srcu_struct *ssp) { unsigned long flags; /* The smp_load_acquire() pairs with the smp_store_release(). */ - if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/ + if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq_needed))) /*^^^*/ return; /* Already initialized. */ - spin_lock_irqsave_rcu_node(sp, flags); - if (!rcu_seq_state(sp->srcu_gp_seq_needed)) { - spin_unlock_irqrestore_rcu_node(sp, flags); + spin_lock_irqsave_rcu_node(ssp, flags); + if (!rcu_seq_state(ssp->srcu_gp_seq_needed)) { + spin_unlock_irqrestore_rcu_node(ssp, flags); return; } - init_srcu_struct_fields(sp, true); - spin_unlock_irqrestore_rcu_node(sp, flags); + init_srcu_struct_fields(ssp, true); + spin_unlock_irqrestore_rcu_node(ssp, flags); } /* * Returns approximate total of the readers' ->srcu_lock_count[] values * for the rank of per-CPU counters specified by idx. */ -static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx) +static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx) { int cpu; unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); sum += READ_ONCE(cpuc->srcu_lock_count[idx]); } @@ -272,13 +261,13 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx) * Returns approximate total of the readers' ->srcu_unlock_count[] values * for the rank of per-CPU counters specified by idx. */ -static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx) +static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) { int cpu; unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); sum += READ_ONCE(cpuc->srcu_unlock_count[idx]); } @@ -289,11 +278,11 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx) * Return true if the number of pre-existing readers is determined to * be zero. */ -static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) +static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) { unsigned long unlocks; - unlocks = srcu_readers_unlock_idx(sp, idx); + unlocks = srcu_readers_unlock_idx(ssp, idx); /* * Make sure that a lock is always counted if the corresponding @@ -329,25 +318,25 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) * of floor(ULONG_MAX/NR_CPUS/2), which should be sufficient, * especially on 64-bit systems. */ - return srcu_readers_lock_idx(sp, idx) == unlocks; + return srcu_readers_lock_idx(ssp, idx) == unlocks; } /** * srcu_readers_active - returns true if there are readers. and false * otherwise - * @sp: which srcu_struct to count active readers (holding srcu_read_lock). + * @ssp: which srcu_struct to count active readers (holding srcu_read_lock). * * Note that this is not an atomic primitive, and can therefore suffer * severe errors when invoked on an active srcu_struct. That said, it * can be useful as an error check at cleanup time. */ -static bool srcu_readers_active(struct srcu_struct *sp) +static bool srcu_readers_active(struct srcu_struct *ssp) { int cpu; unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); sum += READ_ONCE(cpuc->srcu_lock_count[0]); sum += READ_ONCE(cpuc->srcu_lock_count[1]); @@ -363,44 +352,50 @@ static bool srcu_readers_active(struct srcu_struct *sp) * Return grace-period delay, zero if there are expedited grace * periods pending, SRCU_INTERVAL otherwise. */ -static unsigned long srcu_get_delay(struct srcu_struct *sp) +static unsigned long srcu_get_delay(struct srcu_struct *ssp) { - if (ULONG_CMP_LT(READ_ONCE(sp->srcu_gp_seq), - READ_ONCE(sp->srcu_gp_seq_needed_exp))) + if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), + READ_ONCE(ssp->srcu_gp_seq_needed_exp))) return 0; return SRCU_INTERVAL; } /* Helper for cleanup_srcu_struct() and cleanup_srcu_struct_quiesced(). */ -void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) +void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced) { int cpu; - if (WARN_ON(!srcu_get_delay(sp))) + if (WARN_ON(!srcu_get_delay(ssp))) return; /* Just leak it! */ - if (WARN_ON(srcu_readers_active(sp))) + if (WARN_ON(srcu_readers_active(ssp))) return; /* Just leak it! */ if (quiesced) { - if (WARN_ON(delayed_work_pending(&sp->work))) + if (WARN_ON(delayed_work_pending(&ssp->work))) return; /* Just leak it! */ } else { - flush_delayed_work(&sp->work); + flush_delayed_work(&ssp->work); } - for_each_possible_cpu(cpu) + for_each_possible_cpu(cpu) { + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); + if (quiesced) { - if (WARN_ON(delayed_work_pending(&per_cpu_ptr(sp->sda, cpu)->work))) + if (WARN_ON(timer_pending(&sdp->delay_work))) + return; /* Just leak it! */ + if (WARN_ON(work_pending(&sdp->work))) return; /* Just leak it! */ } else { - flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work); + del_timer_sync(&sdp->delay_work); + flush_work(&sdp->work); } - if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) || - WARN_ON(srcu_readers_active(sp))) { + } + if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) || + WARN_ON(srcu_readers_active(ssp))) { pr_info("%s: Active srcu_struct %p state: %d\n", - __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq))); + __func__, ssp, rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq))); return; /* Caller forgot to stop doing call_srcu()? */ } - free_percpu(sp->sda); - sp->sda = NULL; + free_percpu(ssp->sda); + ssp->sda = NULL; } EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); @@ -409,12 +404,12 @@ EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); * srcu_struct. * Returns an index that must be passed to the matching srcu_read_unlock(). */ -int __srcu_read_lock(struct srcu_struct *sp) +int __srcu_read_lock(struct srcu_struct *ssp) { int idx; - idx = READ_ONCE(sp->srcu_idx) & 0x1; - this_cpu_inc(sp->sda->srcu_lock_count[idx]); + idx = READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx]); smp_mb(); /* B */ /* Avoid leaking the critical section. */ return idx; } @@ -425,10 +420,10 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock); * element of the srcu_struct. Note that this may well be a different * CPU than that which was incremented by the corresponding srcu_read_lock(). */ -void __srcu_read_unlock(struct srcu_struct *sp, int idx) +void __srcu_read_unlock(struct srcu_struct *ssp, int idx) { smp_mb(); /* C */ /* Avoid leaking the critical section. */ - this_cpu_inc(sp->sda->srcu_unlock_count[idx]); + this_cpu_inc(ssp->sda->srcu_unlock_count[idx]); } EXPORT_SYMBOL_GPL(__srcu_read_unlock); @@ -444,56 +439,42 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock); /* * Start an SRCU grace period. */ -static void srcu_gp_start(struct srcu_struct *sp) +static void srcu_gp_start(struct srcu_struct *ssp) { - struct srcu_data *sdp = this_cpu_ptr(sp->sda); + struct srcu_data *sdp = this_cpu_ptr(ssp->sda); int state; - lockdep_assert_held(&ACCESS_PRIVATE(sp, lock)); - WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); + lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock)); + WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)); + spin_lock_rcu_node(sdp); /* Interrupts already disabled. */ rcu_segcblist_advance(&sdp->srcu_cblist, - rcu_seq_current(&sp->srcu_gp_seq)); + rcu_seq_current(&ssp->srcu_gp_seq)); (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&sp->srcu_gp_seq)); + rcu_seq_snap(&ssp->srcu_gp_seq)); + spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */ smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */ - rcu_seq_start(&sp->srcu_gp_seq); - state = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); + rcu_seq_start(&ssp->srcu_gp_seq); + state = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)); WARN_ON_ONCE(state != SRCU_STATE_SCAN1); } -/* - * Track online CPUs to guide callback workqueue placement. - */ -DEFINE_PER_CPU(bool, srcu_online); -void srcu_online_cpu(unsigned int cpu) +static void srcu_delay_timer(struct timer_list *t) { - WRITE_ONCE(per_cpu(srcu_online, cpu), true); -} + struct srcu_data *sdp = container_of(t, struct srcu_data, delay_work); -void srcu_offline_cpu(unsigned int cpu) -{ - WRITE_ONCE(per_cpu(srcu_online, cpu), false); + queue_work_on(sdp->cpu, rcu_gp_wq, &sdp->work); } -/* - * Place the workqueue handler on the specified CPU if online, otherwise - * just run it whereever. This is useful for placing workqueue handlers - * that are to invoke the specified CPU's callbacks. - */ -static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, - struct delayed_work *dwork, +static void srcu_queue_delayed_work_on(struct srcu_data *sdp, unsigned long delay) { - bool ret; + if (!delay) { + queue_work_on(sdp->cpu, rcu_gp_wq, &sdp->work); + return; + } - preempt_disable(); - if (READ_ONCE(per_cpu(srcu_online, cpu))) - ret = queue_delayed_work_on(cpu, wq, dwork, delay); - else - ret = queue_delayed_work(wq, dwork, delay); - preempt_enable(); - return ret; + timer_reduce(&sdp->delay_work, jiffies + delay); } /* @@ -502,7 +483,7 @@ static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, */ static void srcu_schedule_cbs_sdp(struct srcu_data *sdp, unsigned long delay) { - srcu_queue_delayed_work_on(sdp->cpu, rcu_gp_wq, &sdp->work, delay); + srcu_queue_delayed_work_on(sdp, delay); } /* @@ -511,7 +492,7 @@ static void srcu_schedule_cbs_sdp(struct srcu_data *sdp, unsigned long delay) * just-completed grace period, the one corresponding to idx. If possible, * schedule this invocation on the corresponding CPUs. */ -static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp, +static void srcu_schedule_cbs_snp(struct srcu_struct *ssp, struct srcu_node *snp, unsigned long mask, unsigned long delay) { int cpu; @@ -519,7 +500,7 @@ static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp, for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { if (!(mask & (1 << (cpu - snp->grplo)))) continue; - srcu_schedule_cbs_sdp(per_cpu_ptr(sp->sda, cpu), delay); + srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, cpu), delay); } } @@ -532,7 +513,7 @@ static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp, * are initiating callback invocation. This allows the ->srcu_have_cbs[] * array to have a finite number of elements. */ -static void srcu_gp_end(struct srcu_struct *sp) +static void srcu_gp_end(struct srcu_struct *ssp) { unsigned long cbdelay; bool cbs; @@ -546,28 +527,28 @@ static void srcu_gp_end(struct srcu_struct *sp) struct srcu_node *snp; /* Prevent more than one additional grace period. */ - mutex_lock(&sp->srcu_cb_mutex); + mutex_lock(&ssp->srcu_cb_mutex); /* End the current grace period. */ - spin_lock_irq_rcu_node(sp); - idx = rcu_seq_state(sp->srcu_gp_seq); + spin_lock_irq_rcu_node(ssp); + idx = rcu_seq_state(ssp->srcu_gp_seq); WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); - cbdelay = srcu_get_delay(sp); - sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); - rcu_seq_end(&sp->srcu_gp_seq); - gpseq = rcu_seq_current(&sp->srcu_gp_seq); - if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, gpseq)) - sp->srcu_gp_seq_needed_exp = gpseq; - spin_unlock_irq_rcu_node(sp); - mutex_unlock(&sp->srcu_gp_mutex); + cbdelay = srcu_get_delay(ssp); + ssp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + rcu_seq_end(&ssp->srcu_gp_seq); + gpseq = rcu_seq_current(&ssp->srcu_gp_seq); + if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq)) + ssp->srcu_gp_seq_needed_exp = gpseq; + spin_unlock_irq_rcu_node(ssp); + mutex_unlock(&ssp->srcu_gp_mutex); /* A new grace period can start at this point. But only one. */ /* Initiate callback invocation as needed. */ idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); - srcu_for_each_node_breadth_first(sp, snp) { + srcu_for_each_node_breadth_first(ssp, snp) { spin_lock_irq_rcu_node(snp); cbs = false; - last_lvl = snp >= sp->level[rcu_num_lvls - 1]; + last_lvl = snp >= ssp->level[rcu_num_lvls - 1]; if (last_lvl) cbs = snp->srcu_have_cbs[idx] == gpseq; snp->srcu_have_cbs[idx] = gpseq; @@ -578,12 +559,12 @@ static void srcu_gp_end(struct srcu_struct *sp) snp->srcu_data_have_cbs[idx] = 0; spin_unlock_irq_rcu_node(snp); if (cbs) - srcu_schedule_cbs_snp(sp, snp, mask, cbdelay); + srcu_schedule_cbs_snp(ssp, snp, mask, cbdelay); /* Occasionally prevent srcu_data counter wrap. */ if (!(gpseq & counter_wrap_check) && last_lvl) for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { - sdp = per_cpu_ptr(sp->sda, cpu); + sdp = per_cpu_ptr(ssp->sda, cpu); spin_lock_irqsave_rcu_node(sdp, flags); if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed + 100)) @@ -596,18 +577,18 @@ static void srcu_gp_end(struct srcu_struct *sp) } /* Callback initiation done, allow grace periods after next. */ - mutex_unlock(&sp->srcu_cb_mutex); + mutex_unlock(&ssp->srcu_cb_mutex); /* Start a new grace period if needed. */ - spin_lock_irq_rcu_node(sp); - gpseq = rcu_seq_current(&sp->srcu_gp_seq); + spin_lock_irq_rcu_node(ssp); + gpseq = rcu_seq_current(&ssp->srcu_gp_seq); if (!rcu_seq_state(gpseq) && - ULONG_CMP_LT(gpseq, sp->srcu_gp_seq_needed)) { - srcu_gp_start(sp); - spin_unlock_irq_rcu_node(sp); - srcu_reschedule(sp, 0); + ULONG_CMP_LT(gpseq, ssp->srcu_gp_seq_needed)) { + srcu_gp_start(ssp); + spin_unlock_irq_rcu_node(ssp); + srcu_reschedule(ssp, 0); } else { - spin_unlock_irq_rcu_node(sp); + spin_unlock_irq_rcu_node(ssp); } } @@ -618,13 +599,13 @@ static void srcu_gp_end(struct srcu_struct *sp) * but without expediting. To start a completely new grace period, * whether expedited or not, use srcu_funnel_gp_start() instead. */ -static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, +static void srcu_funnel_exp_start(struct srcu_struct *ssp, struct srcu_node *snp, unsigned long s) { unsigned long flags; for (; snp != NULL; snp = snp->srcu_parent) { - if (rcu_seq_done(&sp->srcu_gp_seq, s) || + if (rcu_seq_done(&ssp->srcu_gp_seq, s) || ULONG_CMP_GE(READ_ONCE(snp->srcu_gp_seq_needed_exp), s)) return; spin_lock_irqsave_rcu_node(snp, flags); @@ -635,10 +616,10 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s); spin_unlock_irqrestore_rcu_node(snp, flags); } - spin_lock_irqsave_rcu_node(sp, flags); - if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) - sp->srcu_gp_seq_needed_exp = s; - spin_unlock_irqrestore_rcu_node(sp, flags); + spin_lock_irqsave_rcu_node(ssp, flags); + if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s)) + ssp->srcu_gp_seq_needed_exp = s; + spin_unlock_irqrestore_rcu_node(ssp, flags); } /* @@ -651,7 +632,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, * Note that this function also does the work of srcu_funnel_exp_start(), * in some cases by directly invoking it. */ -static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, +static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, unsigned long s, bool do_norm) { unsigned long flags; @@ -661,7 +642,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, /* Each pass through the loop does one level of the srcu_node tree. */ for (; snp != NULL; snp = snp->srcu_parent) { - if (rcu_seq_done(&sp->srcu_gp_seq, s) && snp != sdp->mynode) + if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != sdp->mynode) return; /* GP already done and CBs recorded. */ spin_lock_irqsave_rcu_node(snp, flags); if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) { @@ -676,7 +657,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, return; } if (!do_norm) - srcu_funnel_exp_start(sp, snp, s); + srcu_funnel_exp_start(ssp, snp, s); return; } snp->srcu_have_cbs[idx] = s; @@ -688,29 +669,29 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, } /* Top of tree, must ensure the grace period will be started. */ - spin_lock_irqsave_rcu_node(sp, flags); - if (ULONG_CMP_LT(sp->srcu_gp_seq_needed, s)) { + spin_lock_irqsave_rcu_node(ssp, flags); + if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed, s)) { /* * Record need for grace period s. Pair with load * acquire setting up for initialization. */ - smp_store_release(&sp->srcu_gp_seq_needed, s); /*^^^*/ + smp_store_release(&ssp->srcu_gp_seq_needed, s); /*^^^*/ } - if (!do_norm && ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) - sp->srcu_gp_seq_needed_exp = s; + if (!do_norm && ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s)) + ssp->srcu_gp_seq_needed_exp = s; /* If grace period not already done and none in progress, start it. */ - if (!rcu_seq_done(&sp->srcu_gp_seq, s) && - rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) { - WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); - srcu_gp_start(sp); + if (!rcu_seq_done(&ssp->srcu_gp_seq, s) && + rcu_seq_state(ssp->srcu_gp_seq) == SRCU_STATE_IDLE) { + WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)); + srcu_gp_start(ssp); if (likely(srcu_init_done)) - queue_delayed_work(rcu_gp_wq, &sp->work, - srcu_get_delay(sp)); - else if (list_empty(&sp->work.work.entry)) - list_add(&sp->work.work.entry, &srcu_boot_list); + queue_delayed_work(rcu_gp_wq, &ssp->work, + srcu_get_delay(ssp)); + else if (list_empty(&ssp->work.work.entry)) + list_add(&ssp->work.work.entry, &srcu_boot_list); } - spin_unlock_irqrestore_rcu_node(sp, flags); + spin_unlock_irqrestore_rcu_node(ssp, flags); } /* @@ -718,12 +699,12 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, * loop an additional time if there is an expedited grace period pending. * The caller must ensure that ->srcu_idx is not changed while checking. */ -static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) +static bool try_check_zero(struct srcu_struct *ssp, int idx, int trycount) { for (;;) { - if (srcu_readers_active_idx_check(sp, idx)) + if (srcu_readers_active_idx_check(ssp, idx)) return true; - if (--trycount + !srcu_get_delay(sp) <= 0) + if (--trycount + !srcu_get_delay(ssp) <= 0) return false; udelay(SRCU_RETRY_CHECK_DELAY); } @@ -734,7 +715,7 @@ static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) * use the other rank of the ->srcu_(un)lock_count[] arrays. This allows * us to wait for pre-existing readers in a starvation-free manner. */ -static void srcu_flip(struct srcu_struct *sp) +static void srcu_flip(struct srcu_struct *ssp) { /* * Ensure that if this updater saw a given reader's increment @@ -746,7 +727,7 @@ static void srcu_flip(struct srcu_struct *sp) */ smp_mb(); /* E */ /* Pairs with B and C. */ - WRITE_ONCE(sp->srcu_idx, sp->srcu_idx + 1); + WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1); /* * Ensure that if the updater misses an __srcu_read_unlock() @@ -779,7 +760,7 @@ static void srcu_flip(struct srcu_struct *sp) * negligible when amoritized over that time period, and the extra latency * of a needlessly non-expedited grace period is similarly negligible. */ -static bool srcu_might_be_idle(struct srcu_struct *sp) +static bool srcu_might_be_idle(struct srcu_struct *ssp) { unsigned long curseq; unsigned long flags; @@ -788,7 +769,7 @@ static bool srcu_might_be_idle(struct srcu_struct *sp) /* If the local srcu_data structure has callbacks, not idle. */ local_irq_save(flags); - sdp = this_cpu_ptr(sp->sda); + sdp = this_cpu_ptr(ssp->sda); if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) { local_irq_restore(flags); return false; /* Callbacks already present, so not idle. */ @@ -804,17 +785,17 @@ static bool srcu_might_be_idle(struct srcu_struct *sp) /* First, see if enough time has passed since the last GP. */ t = ktime_get_mono_fast_ns(); if (exp_holdoff == 0 || - time_in_range_open(t, sp->srcu_last_gp_end, - sp->srcu_last_gp_end + exp_holdoff)) + time_in_range_open(t, ssp->srcu_last_gp_end, + ssp->srcu_last_gp_end + exp_holdoff)) return false; /* Too soon after last GP. */ /* Next, check for probable idleness. */ - curseq = rcu_seq_current(&sp->srcu_gp_seq); + curseq = rcu_seq_current(&ssp->srcu_gp_seq); smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */ - if (ULONG_CMP_LT(curseq, READ_ONCE(sp->srcu_gp_seq_needed))) + if (ULONG_CMP_LT(curseq, READ_ONCE(ssp->srcu_gp_seq_needed))) return false; /* Grace period in progress, so not idle. */ smp_mb(); /* Order ->srcu_gp_seq with prior access. */ - if (curseq != rcu_seq_current(&sp->srcu_gp_seq)) + if (curseq != rcu_seq_current(&ssp->srcu_gp_seq)) return false; /* GP # changed, so not idle. */ return true; /* With reasonable probability, idle! */ } @@ -854,16 +835,17 @@ static void srcu_leak_callback(struct rcu_head *rhp) * srcu_read_lock(), and srcu_read_unlock() that are all passed the same * srcu_struct structure. */ -void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, +void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, rcu_callback_t func, bool do_norm) { unsigned long flags; + int idx; bool needexp = false; bool needgp = false; unsigned long s; struct srcu_data *sdp; - check_init_srcu_struct(sp); + check_init_srcu_struct(ssp); if (debug_rcu_head_queue(rhp)) { /* Probable double call_srcu(), so leak the callback. */ WRITE_ONCE(rhp->func, srcu_leak_callback); @@ -871,13 +853,14 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, return; } rhp->func = func; + idx = srcu_read_lock(ssp); local_irq_save(flags); - sdp = this_cpu_ptr(sp->sda); + sdp = this_cpu_ptr(ssp->sda); spin_lock_rcu_node(sdp); rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false); rcu_segcblist_advance(&sdp->srcu_cblist, - rcu_seq_current(&sp->srcu_gp_seq)); - s = rcu_seq_snap(&sp->srcu_gp_seq); + rcu_seq_current(&ssp->srcu_gp_seq)); + s = rcu_seq_snap(&ssp->srcu_gp_seq); (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s); if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) { sdp->srcu_gp_seq_needed = s; @@ -889,14 +872,15 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, } spin_unlock_irqrestore_rcu_node(sdp, flags); if (needgp) - srcu_funnel_gp_start(sp, sdp, s, do_norm); + srcu_funnel_gp_start(ssp, sdp, s, do_norm); else if (needexp) - srcu_funnel_exp_start(sp, sdp->mynode, s); + srcu_funnel_exp_start(ssp, sdp->mynode, s); + srcu_read_unlock(ssp, idx); } /** * call_srcu() - Queue a callback for invocation after an SRCU grace period - * @sp: srcu_struct in queue the callback + * @ssp: srcu_struct in queue the callback * @rhp: structure to be used for queueing the SRCU callback. * @func: function to be invoked after the SRCU grace period * @@ -911,21 +895,21 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, * The callback will be invoked from process context, but must nevertheless * be fast and must not block. */ -void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, +void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, rcu_callback_t func) { - __call_srcu(sp, rhp, func, true); + __call_srcu(ssp, rhp, func, true); } EXPORT_SYMBOL_GPL(call_srcu); /* * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). */ -static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) +static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm) { struct rcu_synchronize rcu; - RCU_LOCKDEP_WARN(lock_is_held(&sp->dep_map) || + RCU_LOCKDEP_WARN(lock_is_held(&ssp->dep_map) || lock_is_held(&rcu_bh_lock_map) || lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map), @@ -934,10 +918,10 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return; might_sleep(); - check_init_srcu_struct(sp); + check_init_srcu_struct(ssp); init_completion(&rcu.completion); init_rcu_head_on_stack(&rcu.head); - __call_srcu(sp, &rcu.head, wakeme_after_rcu, do_norm); + __call_srcu(ssp, &rcu.head, wakeme_after_rcu, do_norm); wait_for_completion(&rcu.completion); destroy_rcu_head_on_stack(&rcu.head); @@ -953,7 +937,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) /** * synchronize_srcu_expedited - Brute-force SRCU grace period - * @sp: srcu_struct with which to synchronize. + * @ssp: srcu_struct with which to synchronize. * * Wait for an SRCU grace period to elapse, but be more aggressive about * spinning rather than blocking when waiting. @@ -961,15 +945,15 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) * Note that synchronize_srcu_expedited() has the same deadlock and * memory-ordering properties as does synchronize_srcu(). */ -void synchronize_srcu_expedited(struct srcu_struct *sp) +void synchronize_srcu_expedited(struct srcu_struct *ssp) { - __synchronize_srcu(sp, rcu_gp_is_normal()); + __synchronize_srcu(ssp, rcu_gp_is_normal()); } EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); /** * synchronize_srcu - wait for prior SRCU read-side critical-section completion - * @sp: srcu_struct with which to synchronize. + * @ssp: srcu_struct with which to synchronize. * * Wait for the count to drain to zero of both indexes. To avoid the * possible starvation of synchronize_srcu(), it waits for the count of @@ -1011,12 +995,12 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); * SRCU must also provide it. Note that detecting idleness is heuristic * and subject to both false positives and negatives. */ -void synchronize_srcu(struct srcu_struct *sp) +void synchronize_srcu(struct srcu_struct *ssp) { - if (srcu_might_be_idle(sp) || rcu_gp_is_expedited()) - synchronize_srcu_expedited(sp); + if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited()) + synchronize_srcu_expedited(ssp); else - __synchronize_srcu(sp, true); + __synchronize_srcu(ssp, true); } EXPORT_SYMBOL_GPL(synchronize_srcu); @@ -1026,36 +1010,36 @@ EXPORT_SYMBOL_GPL(synchronize_srcu); static void srcu_barrier_cb(struct rcu_head *rhp) { struct srcu_data *sdp; - struct srcu_struct *sp; + struct srcu_struct *ssp; sdp = container_of(rhp, struct srcu_data, srcu_barrier_head); - sp = sdp->sp; - if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) - complete(&sp->srcu_barrier_completion); + ssp = sdp->ssp; + if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt)) + complete(&ssp->srcu_barrier_completion); } /** * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. - * @sp: srcu_struct on which to wait for in-flight callbacks. + * @ssp: srcu_struct on which to wait for in-flight callbacks. */ -void srcu_barrier(struct srcu_struct *sp) +void srcu_barrier(struct srcu_struct *ssp) { int cpu; struct srcu_data *sdp; - unsigned long s = rcu_seq_snap(&sp->srcu_barrier_seq); + unsigned long s = rcu_seq_snap(&ssp->srcu_barrier_seq); - check_init_srcu_struct(sp); - mutex_lock(&sp->srcu_barrier_mutex); - if (rcu_seq_done(&sp->srcu_barrier_seq, s)) { + check_init_srcu_struct(ssp); + mutex_lock(&ssp->srcu_barrier_mutex); + if (rcu_seq_done(&ssp->srcu_barrier_seq, s)) { smp_mb(); /* Force ordering following return. */ - mutex_unlock(&sp->srcu_barrier_mutex); + mutex_unlock(&ssp->srcu_barrier_mutex); return; /* Someone else did our work for us. */ } - rcu_seq_start(&sp->srcu_barrier_seq); - init_completion(&sp->srcu_barrier_completion); + rcu_seq_start(&ssp->srcu_barrier_seq); + init_completion(&ssp->srcu_barrier_completion); /* Initial count prevents reaching zero until all CBs are posted. */ - atomic_set(&sp->srcu_barrier_cpu_cnt, 1); + atomic_set(&ssp->srcu_barrier_cpu_cnt, 1); /* * Each pass through this loop enqueues a callback, but only @@ -1066,39 +1050,39 @@ void srcu_barrier(struct srcu_struct *sp) * grace period as the last callback already in the queue. */ for_each_possible_cpu(cpu) { - sdp = per_cpu_ptr(sp->sda, cpu); + sdp = per_cpu_ptr(ssp->sda, cpu); spin_lock_irq_rcu_node(sdp); - atomic_inc(&sp->srcu_barrier_cpu_cnt); + atomic_inc(&ssp->srcu_barrier_cpu_cnt); sdp->srcu_barrier_head.func = srcu_barrier_cb; debug_rcu_head_queue(&sdp->srcu_barrier_head); if (!rcu_segcblist_entrain(&sdp->srcu_cblist, &sdp->srcu_barrier_head, 0)) { debug_rcu_head_unqueue(&sdp->srcu_barrier_head); - atomic_dec(&sp->srcu_barrier_cpu_cnt); + atomic_dec(&ssp->srcu_barrier_cpu_cnt); } spin_unlock_irq_rcu_node(sdp); } /* Remove the initial count, at which point reaching zero can happen. */ - if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) - complete(&sp->srcu_barrier_completion); - wait_for_completion(&sp->srcu_barrier_completion); + if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt)) + complete(&ssp->srcu_barrier_completion); + wait_for_completion(&ssp->srcu_barrier_completion); - rcu_seq_end(&sp->srcu_barrier_seq); - mutex_unlock(&sp->srcu_barrier_mutex); + rcu_seq_end(&ssp->srcu_barrier_seq); + mutex_unlock(&ssp->srcu_barrier_mutex); } EXPORT_SYMBOL_GPL(srcu_barrier); /** * srcu_batches_completed - return batches completed. - * @sp: srcu_struct on which to report batch completion. + * @ssp: srcu_struct on which to report batch completion. * * Report the number of batches, correlated with, but not necessarily * precisely the same as, the number of grace periods that have elapsed. */ -unsigned long srcu_batches_completed(struct srcu_struct *sp) +unsigned long srcu_batches_completed(struct srcu_struct *ssp) { - return sp->srcu_idx; + return ssp->srcu_idx; } EXPORT_SYMBOL_GPL(srcu_batches_completed); @@ -1107,11 +1091,11 @@ EXPORT_SYMBOL_GPL(srcu_batches_completed); * to SRCU_STATE_SCAN2, and invoke srcu_gp_end() when scan has * completed in that state. */ -static void srcu_advance_state(struct srcu_struct *sp) +static void srcu_advance_state(struct srcu_struct *ssp) { int idx; - mutex_lock(&sp->srcu_gp_mutex); + mutex_lock(&ssp->srcu_gp_mutex); /* * Because readers might be delayed for an extended period after @@ -1123,47 +1107,47 @@ static void srcu_advance_state(struct srcu_struct *sp) * The load-acquire ensures that we see the accesses performed * by the prior grace period. */ - idx = rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq)); /* ^^^ */ + idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq)); /* ^^^ */ if (idx == SRCU_STATE_IDLE) { - spin_lock_irq_rcu_node(sp); - if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { - WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq)); - spin_unlock_irq_rcu_node(sp); - mutex_unlock(&sp->srcu_gp_mutex); + spin_lock_irq_rcu_node(ssp); + if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) { + WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq)); + spin_unlock_irq_rcu_node(ssp); + mutex_unlock(&ssp->srcu_gp_mutex); return; } - idx = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); + idx = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)); if (idx == SRCU_STATE_IDLE) - srcu_gp_start(sp); - spin_unlock_irq_rcu_node(sp); + srcu_gp_start(ssp); + spin_unlock_irq_rcu_node(ssp); if (idx != SRCU_STATE_IDLE) { - mutex_unlock(&sp->srcu_gp_mutex); + mutex_unlock(&ssp->srcu_gp_mutex); return; /* Someone else started the grace period. */ } } - if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN1) { - idx = 1 ^ (sp->srcu_idx & 1); - if (!try_check_zero(sp, idx, 1)) { - mutex_unlock(&sp->srcu_gp_mutex); + if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN1) { + idx = 1 ^ (ssp->srcu_idx & 1); + if (!try_check_zero(ssp, idx, 1)) { + mutex_unlock(&ssp->srcu_gp_mutex); return; /* readers present, retry later. */ } - srcu_flip(sp); - rcu_seq_set_state(&sp->srcu_gp_seq, SRCU_STATE_SCAN2); + srcu_flip(ssp); + rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2); } - if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN2) { + if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) { /* * SRCU read-side critical sections are normally short, * so check at least twice in quick succession after a flip. */ - idx = 1 ^ (sp->srcu_idx & 1); - if (!try_check_zero(sp, idx, 2)) { - mutex_unlock(&sp->srcu_gp_mutex); + idx = 1 ^ (ssp->srcu_idx & 1); + if (!try_check_zero(ssp, idx, 2)) { + mutex_unlock(&ssp->srcu_gp_mutex); return; /* readers present, retry later. */ } - srcu_gp_end(sp); /* Releases ->srcu_gp_mutex. */ + srcu_gp_end(ssp); /* Releases ->srcu_gp_mutex. */ } } @@ -1179,14 +1163,15 @@ static void srcu_invoke_callbacks(struct work_struct *work) struct rcu_cblist ready_cbs; struct rcu_head *rhp; struct srcu_data *sdp; - struct srcu_struct *sp; + struct srcu_struct *ssp; + + sdp = container_of(work, struct srcu_data, work); - sdp = container_of(work, struct srcu_data, work.work); - sp = sdp->sp; + ssp = sdp->ssp; rcu_cblist_init(&ready_cbs); spin_lock_irq_rcu_node(sdp); rcu_segcblist_advance(&sdp->srcu_cblist, - rcu_seq_current(&sp->srcu_gp_seq)); + rcu_seq_current(&ssp->srcu_gp_seq)); if (sdp->srcu_cblist_invoking || !rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) { spin_unlock_irq_rcu_node(sdp); @@ -1212,7 +1197,7 @@ static void srcu_invoke_callbacks(struct work_struct *work) spin_lock_irq_rcu_node(sdp); rcu_segcblist_insert_count(&sdp->srcu_cblist, &ready_cbs); (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&sp->srcu_gp_seq)); + rcu_seq_snap(&ssp->srcu_gp_seq)); sdp->srcu_cblist_invoking = false; more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); spin_unlock_irq_rcu_node(sdp); @@ -1224,24 +1209,24 @@ static void srcu_invoke_callbacks(struct work_struct *work) * Finished one round of SRCU grace period. Start another if there are * more SRCU callbacks queued, otherwise put SRCU into not-running state. */ -static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) +static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay) { bool pushgp = true; - spin_lock_irq_rcu_node(sp); - if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { - if (!WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq))) { + spin_lock_irq_rcu_node(ssp); + if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) { + if (!WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq))) { /* All requests fulfilled, time to go idle. */ pushgp = false; } - } else if (!rcu_seq_state(sp->srcu_gp_seq)) { + } else if (!rcu_seq_state(ssp->srcu_gp_seq)) { /* Outstanding request and no GP. Start one. */ - srcu_gp_start(sp); + srcu_gp_start(ssp); } - spin_unlock_irq_rcu_node(sp); + spin_unlock_irq_rcu_node(ssp); if (pushgp) - queue_delayed_work(rcu_gp_wq, &sp->work, delay); + queue_delayed_work(rcu_gp_wq, &ssp->work, delay); } /* @@ -1249,41 +1234,41 @@ static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) */ static void process_srcu(struct work_struct *work) { - struct srcu_struct *sp; + struct srcu_struct *ssp; - sp = container_of(work, struct srcu_struct, work.work); + ssp = container_of(work, struct srcu_struct, work.work); - srcu_advance_state(sp); - srcu_reschedule(sp, srcu_get_delay(sp)); + srcu_advance_state(ssp); + srcu_reschedule(ssp, srcu_get_delay(ssp)); } void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *sp, int *flags, + struct srcu_struct *ssp, int *flags, unsigned long *gp_seq) { if (test_type != SRCU_FLAVOR) return; *flags = 0; - *gp_seq = rcu_seq_current(&sp->srcu_gp_seq); + *gp_seq = rcu_seq_current(&ssp->srcu_gp_seq); } EXPORT_SYMBOL_GPL(srcutorture_get_gp_data); -void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf) +void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) { int cpu; int idx; unsigned long s0 = 0, s1 = 0; - idx = sp->srcu_idx & 0x1; + idx = ssp->srcu_idx & 0x1; pr_alert("%s%s Tree SRCU g%ld per-CPU(idx=%d):", - tt, tf, rcu_seq_current(&sp->srcu_gp_seq), idx); + tt, tf, rcu_seq_current(&ssp->srcu_gp_seq), idx); for_each_possible_cpu(cpu) { unsigned long l0, l1; unsigned long u0, u1; long c0, c1; struct srcu_data *sdp; - sdp = per_cpu_ptr(sp->sda, cpu); + sdp = per_cpu_ptr(ssp->sda, cpu); u0 = sdp->srcu_unlock_count[!idx]; u1 = sdp->srcu_unlock_count[idx]; @@ -1318,14 +1303,14 @@ early_initcall(srcu_bootup_announce); void __init srcu_init(void) { - struct srcu_struct *sp; + struct srcu_struct *ssp; srcu_init_done = true; while (!list_empty(&srcu_boot_list)) { - sp = list_first_entry(&srcu_boot_list, struct srcu_struct, + ssp = list_first_entry(&srcu_boot_list, struct srcu_struct, work.work.entry); - check_init_srcu_struct(sp); - list_del_init(&sp->work.work.entry); - queue_work(rcu_gp_wq, &sp->work.work); + check_init_srcu_struct(ssp); + list_del_init(&ssp->work.work.entry); + queue_work(rcu_gp_wq, &ssp->work.work); } } diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 3f943efcf61c..a8304d90573f 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -1,20 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * RCU-based infrastructure for lightweight reader-writer locking * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (c) 2015, Red Hat, Inc. * * Author: Oleg Nesterov <[email protected]> @@ -44,15 +31,15 @@ static const struct { __INIT_HELD(rcu_read_lock_held) }, [RCU_SCHED_SYNC] = { - .sync = synchronize_sched, - .call = call_rcu_sched, - .wait = rcu_barrier_sched, + .sync = synchronize_rcu, + .call = call_rcu, + .wait = rcu_barrier, __INIT_HELD(rcu_read_lock_sched_held) }, [RCU_BH_SYNC] = { - .sync = synchronize_rcu_bh, - .call = call_rcu_bh, - .wait = rcu_barrier_bh, + .sync = synchronize_rcu, + .call = call_rcu, + .wait = rcu_barrier, __INIT_HELD(rcu_read_lock_bh_held) }, }; @@ -125,8 +112,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) rsp->gp_state = GP_PENDING; spin_unlock_irq(&rsp->rss_lock); - BUG_ON(need_wait && need_sync); - + WARN_ON_ONCE(need_wait && need_sync); if (need_sync) { gp_ops[rsp->gp_type].sync(); rsp->gp_state = GP_PASSED; @@ -139,7 +125,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) * Nobody has yet been allowed the 'fast' path and thus we can * avoid doing any sync(). The callback will get 'dropped'. */ - BUG_ON(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); } } @@ -166,8 +152,8 @@ static void rcu_sync_func(struct rcu_head *rhp) struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head); unsigned long flags; - BUG_ON(rsp->gp_state != GP_PASSED); - BUG_ON(rsp->cb_state == CB_IDLE); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->cb_state == CB_IDLE); spin_lock_irqsave(&rsp->rss_lock, flags); if (rsp->gp_count) { @@ -225,7 +211,7 @@ void rcu_sync_dtor(struct rcu_sync *rsp) { int cb_state; - BUG_ON(rsp->gp_count); + WARN_ON_ONCE(rsp->gp_count); spin_lock_irq(&rsp->rss_lock); if (rsp->cb_state == CB_REPLAY) @@ -235,6 +221,6 @@ void rcu_sync_dtor(struct rcu_sync *rsp) if (cb_state != CB_IDLE) { gp_ops[rsp->gp_type].wait(); - BUG_ON(rsp->cb_state != CB_IDLE); + WARN_ON_ONCE(rsp->cb_state != CB_IDLE); } } diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 5f5963ba313e..911bd9076d43 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * - * Author: Paul E. McKenney <[email protected]> + * Author: Paul E. McKenney <[email protected]> * * For detailed explanation of Read-Copy Update mechanism see - * Documentation/RCU @@ -76,7 +63,7 @@ void rcu_qs(void) * be called from hardirq context. It is normally called from the * scheduling-clock interrupt. */ -void rcu_check_callbacks(int user) +void rcu_sched_clock_irq(int user) { if (user) { rcu_qs(); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 121f833acd04..acd6ccf56faf 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1,27 +1,14 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * * Authors: Dipankar Sarma <[email protected]> * Manfred Spraul <[email protected]> - * Paul E. McKenney <[email protected]> Hierarchical version + * Paul E. McKenney <[email protected]> Hierarchical version * - * Based on the original work by Paul McKenney <[email protected]> + * Based on the original work by Paul McKenney <[email protected]> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * * For detailed explanation of Read-Copy Update mechanism see - @@ -62,6 +49,8 @@ #include <linux/suspend.h> #include <linux/ftrace.h> #include <linux/tick.h> +#include <linux/sysrq.h> +#include <linux/kprobes.h> #include "tree.h" #include "rcu.h" @@ -115,6 +104,9 @@ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ /* panic() on RCU Stall sysctl. */ int sysctl_panic_on_rcu_stall __read_mostly; +/* Commandeer a sysrq key to dump RCU's tree. */ +static bool sysrq_rcu; +module_param(sysrq_rcu, bool, 0444); /* * The rcu_scheduler_active variable is initialized to the value @@ -207,6 +199,19 @@ static int rcu_gp_in_progress(void) return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq)); } +/* + * Return the number of callbacks queued on the specified CPU. + * Handles both the nocbs and normal cases. + */ +static long rcu_get_n_cbs_cpu(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + if (rcu_segcblist_is_enabled(&rdp->cblist)) /* Online normal CPU? */ + return rcu_segcblist_n_cbs(&rdp->cblist); + return rcu_get_n_cbs_nocb_cpu(rdp); /* Works for offline, too. */ +} + void rcu_softirq_qs(void) { rcu_qs(); @@ -466,7 +471,6 @@ module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next module_param(rcu_kick_kthreads, bool, 0644); static void force_qs_rnp(int (*f)(struct rcu_data *rdp)); -static void force_quiescent_state(void); static int rcu_pending(void); /* @@ -491,13 +495,22 @@ unsigned long rcu_exp_batches_completed(void) EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); /* - * Force a quiescent state. + * Return the root node of the rcu_state structure. */ -void rcu_force_quiescent_state(void) +static struct rcu_node *rcu_get_root(void) { - force_quiescent_state(); + return &rcu_state.node[0]; +} + +/* + * Convert a ->gp_state value to a character string. + */ +static const char *gp_state_getname(short gs) +{ + if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names)) + return "???"; + return gp_state_names[gs]; } -EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* * Show the state of the grace-period kthreads. @@ -505,17 +518,31 @@ EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); void show_rcu_gp_kthreads(void) { int cpu; + unsigned long j; + unsigned long ja; + unsigned long jr; + unsigned long jw; struct rcu_data *rdp; struct rcu_node *rnp; - pr_info("%s: wait state: %d ->state: %#lx\n", rcu_state.name, - rcu_state.gp_state, rcu_state.gp_kthread->state); + j = jiffies; + ja = j - READ_ONCE(rcu_state.gp_activity); + jr = j - READ_ONCE(rcu_state.gp_req_activity); + jw = j - READ_ONCE(rcu_state.gp_wake_time); + pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", + rcu_state.name, gp_state_getname(rcu_state.gp_state), + rcu_state.gp_state, + rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL, + ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), + (long)READ_ONCE(rcu_state.gp_seq), + (long)READ_ONCE(rcu_get_root()->gp_seq_needed), + READ_ONCE(rcu_state.gp_flags)); rcu_for_each_node_breadth_first(rnp) { if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed)) continue; - pr_info("\trcu_node %d:%d ->gp_seq %lu ->gp_seq_needed %lu\n", - rnp->grplo, rnp->grphi, rnp->gp_seq, - rnp->gp_seq_needed); + pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n", + rnp->grplo, rnp->grphi, (long)rnp->gp_seq, + (long)rnp->gp_seq_needed); if (!rcu_is_leaf_node(rnp)) continue; for_each_leaf_node_possible_cpu(rnp, cpu) { @@ -524,14 +551,35 @@ void show_rcu_gp_kthreads(void) ULONG_CMP_GE(rcu_state.gp_seq, rdp->gp_seq_needed)) continue; - pr_info("\tcpu %d ->gp_seq_needed %lu\n", - cpu, rdp->gp_seq_needed); + pr_info("\tcpu %d ->gp_seq_needed %ld\n", + cpu, (long)rdp->gp_seq_needed); } } /* sched_show_task(rcu_state.gp_kthread); */ } EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); +/* Dump grace-period-request information due to commandeered sysrq. */ +static void sysrq_show_rcu(int key) +{ + show_rcu_gp_kthreads(); +} + +static struct sysrq_key_op sysrq_rcudump_op = { + .handler = sysrq_show_rcu, + .help_msg = "show-rcu(y)", + .action_msg = "Show RCU tree", + .enable_mask = SYSRQ_ENABLE_DUMP, +}; + +static int __init rcu_sysrq_init(void) +{ + if (sysrq_rcu) + return register_sysrq_key('y', &sysrq_rcudump_op); + return 0; +} +early_initcall(rcu_sysrq_init); + /* * Send along grace-period-related data for rcutorture diagnostics. */ @@ -540,8 +588,6 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, { switch (test_type) { case RCU_FLAVOR: - case RCU_BH_FLAVOR: - case RCU_SCHED_FLAVOR: *flags = READ_ONCE(rcu_state.gp_flags); *gp_seq = rcu_seq_current(&rcu_state.gp_seq); break; @@ -552,14 +598,6 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); /* - * Return the root node of the rcu_state structure. - */ -static struct rcu_node *rcu_get_root(void) -{ - return &rcu_state.node[0]; -} - -/* * Enter an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * @@ -675,7 +713,6 @@ static __always_inline void rcu_nmi_exit_common(bool irq) /** * rcu_nmi_exit - inform RCU of exit from NMI context - * @irq: Is this call from rcu_irq_exit? * * If you add or remove a call to rcu_nmi_exit(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. @@ -846,6 +883,7 @@ void rcu_nmi_enter(void) { rcu_nmi_enter_common(false); } +NOKPROBE_SYMBOL(rcu_nmi_enter); /** * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle @@ -891,12 +929,12 @@ void rcu_irq_enter_irqson(void) } /** - * rcu_is_watching - see if RCU thinks that the current CPU is idle + * rcu_is_watching - see if RCU thinks that the current CPU is not idle * * Return true if RCU is watching the running CPU, which means that this * CPU can safely enter RCU read-side critical sections. In other words, - * if the current CPU is in its idle loop and is neither in an interrupt - * or NMI handler, return true. + * if the current CPU is not in its idle loop or is in an interrupt or + * NMI handler, return true. */ bool notrace rcu_is_watching(void) { @@ -1089,7 +1127,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) } /* - * NO_HZ_FULL CPUs can run in-kernel without rcu_check_callbacks! + * NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq! * The above code handles this, but only for straight cond_resched(). * And some in-kernel loops check need_resched() before calling * cond_resched(), which defeats the above code for CPUs that are @@ -1143,16 +1181,6 @@ static void record_gp_stall_check_time(void) } /* - * Convert a ->gp_state value to a character string. - */ -static const char *gp_state_getname(short gs) -{ - if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names)) - return "???"; - return gp_state_names[gs]; -} - -/* * Complain about starvation of grace-period kthread. */ static void rcu_check_gp_kthread_starvation(void) @@ -1165,7 +1193,7 @@ static void rcu_check_gp_kthread_starvation(void) pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), - rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags), gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); if (gpk) { @@ -1262,8 +1290,7 @@ static void print_other_cpu_stall(unsigned long gp_seq) print_cpu_stall_info_end(); for_each_possible_cpu(cpu) - totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(&rcu_data, - cpu)->cblist); + totqlen += rcu_get_n_cbs_cpu(cpu); pr_cont("(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n", smp_processor_id(), (long)(jiffies - rcu_state.gp_start), (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); @@ -1295,7 +1322,7 @@ static void print_other_cpu_stall(unsigned long gp_seq) panic_on_rcu_stall(); - force_quiescent_state(); /* Kick them all. */ + rcu_force_quiescent_state(); /* Kick them all. */ } static void print_cpu_stall(void) @@ -1323,8 +1350,7 @@ static void print_cpu_stall(void) raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); print_cpu_stall_info_end(); for_each_possible_cpu(cpu) - totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(&rcu_data, - cpu)->cblist); + totqlen += rcu_get_n_cbs_cpu(cpu); pr_cont(" (t=%lu jiffies g=%ld q=%lu)\n", jiffies - rcu_state.gp_start, (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); @@ -1543,17 +1569,28 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) } /* - * Awaken the grace-period kthread. Don't do a self-awaken, and don't - * bother awakening when there is nothing for the grace-period kthread - * to do (as in several CPUs raced to awaken, and we lost), and finally - * don't try to awaken a kthread that has not yet been created. + * Awaken the grace-period kthread. Don't do a self-awaken (unless in + * an interrupt or softirq handler), and don't bother awakening when there + * is nothing for the grace-period kthread to do (as in several CPUs raced + * to awaken, and we lost), and finally don't try to awaken a kthread that + * has not yet been created. If all those checks are passed, track some + * debug information and awaken. + * + * So why do the self-wakeup when in an interrupt or softirq handler + * in the grace-period kthread's context? Because the kthread might have + * been interrupted just as it was going to sleep, and just after the final + * pre-sleep check of the awaken condition. In this case, a wakeup really + * is required, and is therefore supplied. */ static void rcu_gp_kthread_wake(void) { - if (current == rcu_state.gp_kthread || + if ((current == rcu_state.gp_kthread && + !in_interrupt() && !in_serving_softirq()) || !READ_ONCE(rcu_state.gp_flags) || !rcu_state.gp_kthread) return; + WRITE_ONCE(rcu_state.gp_wake_time, jiffies); + WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq)); swake_up_one(&rcu_state.gp_wq); } @@ -1697,7 +1734,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) zero_cpu_stall_ticks(rdp); } rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ - if (ULONG_CMP_GE(rnp->gp_seq_needed, rdp->gp_seq_needed) || rdp->gpwrap) + if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) rdp->gp_seq_needed = rnp->gp_seq_needed; WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); @@ -1925,7 +1962,7 @@ static void rcu_gp_fqs_loop(void) if (!ret) { rcu_state.jiffies_force_qs = jiffies + j; WRITE_ONCE(rcu_state.jiffies_kick_kthreads, - jiffies + 3 * j); + jiffies + (j ? 3 * j : 2)); } trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), @@ -1986,7 +2023,8 @@ static void rcu_gp_cleanup(void) WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); - gp_duration = jiffies - rcu_state.gp_start; + rcu_state.gp_end = jiffies; + gp_duration = rcu_state.gp_end - rcu_state.gp_start; if (gp_duration > rcu_state.gp_max) rcu_state.gp_max = gp_duration; @@ -2032,9 +2070,9 @@ static void rcu_gp_cleanup(void) rnp = rcu_get_root(); raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */ - /* Declare grace period done. */ - rcu_seq_end(&rcu_state.gp_seq); + /* Declare grace period done, trace first to use old GP number. */ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end")); + rcu_seq_end(&rcu_state.gp_seq); rcu_state.gp_state = RCU_GP_IDLE; /* Check for GP requests since above loop. */ rdp = this_cpu_ptr(&rcu_data); @@ -2482,14 +2520,14 @@ static void rcu_do_batch(struct rcu_data *rdp) } /* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. + * This function is invoked from each scheduling-clock interrupt, + * and checks to see if this CPU is in a non-context-switch quiescent + * state, for example, user mode or idle loop. It also schedules RCU + * core processing. If the current grace period has gone on too long, + * it will ask the scheduler to manufacture a context switch for the sole + * purpose of providing a providing the needed quiescent state. */ -void rcu_check_callbacks(int user) +void rcu_sched_clock_irq(int user) { trace_rcu_utilization(TPS("Start scheduler-tick")); raw_cpu_inc(rcu_data.ticks_this_gp); @@ -2502,7 +2540,7 @@ void rcu_check_callbacks(int user) } __this_cpu_write(rcu_data.rcu_urgent_qs, false); } - rcu_flavor_check_callbacks(user); + rcu_flavor_sched_clock_irq(user); if (rcu_pending()) invoke_rcu_core(); @@ -2563,7 +2601,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) * Force quiescent states on reluctant CPUs, and also detect which * CPUs are in dyntick-idle mode. */ -static void force_quiescent_state(void) +void rcu_force_quiescent_state(void) { unsigned long flags; bool ret; @@ -2595,15 +2633,16 @@ static void force_quiescent_state(void) raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* * This function checks for grace-period requests that fail to motivate * RCU to come out of its idle mode. */ -static void -rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp) +void +rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, + const unsigned long gpssdelay) { - const unsigned long gpssdelay = rcu_jiffies_till_stall_check() * HZ; unsigned long flags; unsigned long j; struct rcu_node *rnp_root = rcu_get_root(); @@ -2642,24 +2681,57 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } - pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n", - __func__, (long)READ_ONCE(rcu_state.gp_seq), - (long)READ_ONCE(rnp_root->gp_seq_needed), - j - rcu_state.gp_req_activity, j - rcu_state.gp_activity, - rcu_state.gp_flags, rcu_state.gp_state, rcu_state.name, - rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL); WARN_ON(1); if (rnp_root != rnp) raw_spin_unlock_rcu_node(rnp_root); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + show_rcu_gp_kthreads(); } /* - * This does the RCU core processing work for the specified rcu_data - * structures. This may be called only from the CPU to whom the rdp - * belongs. + * Do a forward-progress check for rcutorture. This is normally invoked + * due to an OOM event. The argument "j" gives the time period during + * which rcutorture would like progress to have been made. */ -static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) +void rcu_fwd_progress_check(unsigned long j) +{ + unsigned long cbs; + int cpu; + unsigned long max_cbs = 0; + int max_cpu = -1; + struct rcu_data *rdp; + + if (rcu_gp_in_progress()) { + pr_info("%s: GP age %lu jiffies\n", + __func__, jiffies - rcu_state.gp_start); + show_rcu_gp_kthreads(); + } else { + pr_info("%s: Last GP end %lu jiffies ago\n", + __func__, jiffies - rcu_state.gp_end); + preempt_disable(); + rdp = this_cpu_ptr(&rcu_data); + rcu_check_gp_start_stall(rdp->mynode, rdp, j); + preempt_enable(); + } + for_each_possible_cpu(cpu) { + cbs = rcu_get_n_cbs_cpu(cpu); + if (!cbs) + continue; + if (max_cpu < 0) + pr_info("%s: callbacks", __func__); + pr_cont(" %d: %lu", cpu, cbs); + if (cbs <= max_cbs) + continue; + max_cbs = cbs; + max_cpu = cpu; + } + if (max_cpu >= 0) + pr_cont("\n"); +} +EXPORT_SYMBOL_GPL(rcu_fwd_progress_check); + +/* Perform RCU core processing work for the current CPU. */ +static __latent_entropy void rcu_core(struct softirq_action *unused) { unsigned long flags; struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); @@ -2690,7 +2762,7 @@ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused local_irq_restore(flags); } - rcu_check_gp_start_stall(rnp, rdp); + rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check()); /* If there are callbacks ready, invoke them. */ if (rcu_segcblist_ready_cbs(&rdp->cblist)) @@ -2744,9 +2816,9 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, /* * Force the grace period if too many callbacks or too long waiting. - * Enforce hysteresis, and don't invoke force_quiescent_state() + * Enforce hysteresis, and don't invoke rcu_force_quiescent_state() * if some other CPU has recently done so. Also, don't bother - * invoking force_quiescent_state() if the newly enqueued callback + * invoking rcu_force_quiescent_state() if the newly enqueued callback * is the only one waiting for a grace period to complete. */ if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > @@ -2763,7 +2835,7 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, rdp->blimit = LONG_MAX; if (rcu_state.n_force_qs == rdp->n_force_qs_snap && rcu_segcblist_first_pend_cb(&rdp->cblist) != head) - force_quiescent_state(); + rcu_force_quiescent_state(); rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); } @@ -2826,15 +2898,12 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func, int cpu, bool lazy) * Very early boot, before rcu_init(). Initialize if needed * and then drop through to queue the callback. */ - BUG_ON(cpu != -1); + WARN_ON_ONCE(cpu != -1); WARN_ON_ONCE(!rcu_is_watching()); if (rcu_segcblist_empty(&rdp->cblist)) rcu_segcblist_init(&rdp->cblist); } rcu_segcblist_enqueue(&rdp->cblist, head, lazy); - if (!lazy) - rcu_idle_count_callbacks_posted(); - if (__is_kfree_rcu_offset((unsigned long)func)) trace_rcu_kfree_callback(rcu_state.name, head, (unsigned long)func, @@ -2904,6 +2973,79 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) } EXPORT_SYMBOL_GPL(kfree_call_rcu); +/* + * During early boot, any blocking grace-period wait automatically + * implies a grace period. Later on, this is never the case for PREEMPT. + * + * Howevr, because a context switch is a grace period for !PREEMPT, any + * blocking grace-period wait automatically implies a grace period if + * there is only one CPU online at any point time during execution of + * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to + * occasionally incorrectly indicate that there are multiple CPUs online + * when there was in fact only one the whole time, as this just adds some + * overhead: RCU still operates correctly. + */ +static int rcu_blocking_is_gp(void) +{ + int ret; + + if (IS_ENABLED(CONFIG_PREEMPT)) + return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE; + might_sleep(); /* Check for RCU read-side critical section. */ + preempt_disable(); + ret = num_online_cpus() <= 1; + preempt_enable(); + return ret; +} + +/** + * synchronize_rcu - wait until a grace period has elapsed. + * + * Control will return to the caller some time after a full grace + * period has elapsed, in other words after all currently executing RCU + * read-side critical sections have completed. Note, however, that + * upon return from synchronize_rcu(), the caller might well be executing + * concurrently with new RCU read-side critical sections that began while + * synchronize_rcu() was waiting. RCU read-side critical sections are + * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. + * In addition, regions of code across which interrupts, preemption, or + * softirqs have been disabled also serve as RCU read-side critical + * sections. This includes hardware interrupt handlers, softirq handlers, + * and NMI handlers. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_rcu() returns, + * each CPU is guaranteed to have executed a full memory barrier since + * the end of its last RCU read-side critical section whose beginning + * preceded the call to synchronize_rcu(). In addition, each CPU having + * an RCU read-side critical section that extends beyond the return from + * synchronize_rcu() is guaranteed to have executed a full memory barrier + * after the beginning of synchronize_rcu() and before the beginning of + * that RCU read-side critical section. Note that these guarantees include + * CPUs that are offline, idle, or executing in user mode, as well as CPUs + * that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_rcu(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + */ +void synchronize_rcu(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu() in RCU read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_expedited(); + else + wait_rcu_gp(call_rcu); +} +EXPORT_SYMBOL_GPL(synchronize_rcu); + /** * get_state_synchronize_rcu - Snapshot current RCU state * @@ -2992,28 +3134,6 @@ static int rcu_pending(void) } /* - * Return true if the specified CPU has any callback. If all_lazy is - * non-NULL, store an indication of whether all callbacks are lazy. - * (If there are no callbacks, all of them are deemed to be lazy.) - */ -static bool rcu_cpu_has_callbacks(bool *all_lazy) -{ - bool al = true; - bool hc = false; - struct rcu_data *rdp; - - rdp = this_cpu_ptr(&rcu_data); - if (!rcu_segcblist_empty(&rdp->cblist)) { - hc = true; - if (rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)) - al = false; - } - if (all_lazy) - *all_lazy = al; - return hc; -} - -/* * Helper function for rcu_barrier() tracing. If tracing is disabled, * the compiler is expected to optimize this away. */ @@ -3242,7 +3362,7 @@ int rcutree_prepare_cpu(unsigned int cpu) trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_prepare_kthreads(cpu); - rcu_spawn_all_nocb_kthreads(cpu); + rcu_spawn_cpu_nocb_kthread(cpu); return 0; } @@ -3272,8 +3392,6 @@ int rcutree_online_cpu(unsigned int cpu) raw_spin_lock_irqsave_rcu_node(rnp, flags); rnp->ffmask |= rdp->grpmask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - if (IS_ENABLED(CONFIG_TREE_SRCU)) - srcu_online_cpu(cpu); if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return 0; /* Too early in boot for scheduler work. */ sync_sched_exp_online_cleanup(cpu); @@ -3298,8 +3416,6 @@ int rcutree_offline_cpu(unsigned int cpu) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcutree_affinity_setting(cpu, cpu); - if (IS_ENABLED(CONFIG_TREE_SRCU)) - srcu_offline_cpu(cpu); return 0; } @@ -3485,7 +3601,8 @@ static int __init rcu_spawn_gp_kthread(void) rcu_scheduler_fully_active = 1; t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name); - BUG_ON(IS_ERR(t)); + if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__)) + return 0; rnp = rcu_get_root(); raw_spin_lock_irqsave_rcu_node(rnp, flags); rcu_state.gp_kthread = t; @@ -3719,7 +3836,7 @@ void __init rcu_init(void) rcu_init_one(); if (dump_tree) rcu_dump_rcu_node_tree(); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + open_softirq(RCU_SOFTIRQ, rcu_core); /* * We don't need protection against CPU-hotplug here because diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 703e19ff532d..bb4f995f2d3f 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -1,25 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * * Author: Ingo Molnar <[email protected]> - * Paul E. McKenney <[email protected]> + * Paul E. McKenney <[email protected]> */ #include <linux/cache.h> @@ -36,7 +23,6 @@ /* Communicate arguments to a workqueue handler. */ struct rcu_exp_work { - smp_call_func_t rew_func; unsigned long rew_s; struct work_struct rew_work; }; @@ -57,7 +43,7 @@ struct rcu_node { /* some rcu_state fields as well as */ /* following. */ unsigned long gp_seq; /* Track rsp->rcu_gp_seq. */ - unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed. */ + unsigned long gp_seq_needed; /* Track furthest future GP request. */ unsigned long completedqs; /* All QSes done for this node. */ unsigned long qsmask; /* CPUs or groups that need to switch in */ /* order for current grace period to proceed.*/ @@ -163,7 +149,7 @@ union rcu_noqs { struct rcu_data { /* 1) quiescent-state and grace-period handling : */ unsigned long gp_seq; /* Track rsp->rcu_gp_seq counter. */ - unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed ctr. */ + unsigned long gp_seq_needed; /* Track furthest future GP request. */ union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ bool core_needs_qs; /* Core waits for quiesc state. */ bool beenonline; /* CPU online at least once. */ @@ -194,10 +180,7 @@ struct rcu_data { bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ bool rcu_urgent_qs; /* GP old need light quiescent state. */ #ifdef CONFIG_RCU_FAST_NO_HZ - bool all_lazy; /* Are all CPU's CBs lazy? */ - unsigned long nonlazy_posted; /* # times non-lazy CB posted to CPU. */ - unsigned long nonlazy_posted_snap; - /* Nonlazy_posted snapshot. */ + bool all_lazy; /* All CPU's CBs lazy at idle start? */ unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */ unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */ int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ @@ -234,7 +217,13 @@ struct rcu_data { /* Leader CPU takes GP-end wakeups. */ #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ - /* 6) Diagnostic data, including RCU CPU stall warnings. */ + /* 6) RCU priority boosting. */ + struct task_struct *rcu_cpu_kthread_task; + /* rcuc per-CPU kthread or NULL. */ + unsigned int rcu_cpu_kthread_status; + char rcu_cpu_has_work; + + /* 7) Diagnostic data, including RCU CPU stall warnings. */ unsigned int softirq_snap; /* Snapshot of softirq activity. */ /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ struct irq_work rcu_iw; /* Check for non-irq activity. */ @@ -303,6 +292,8 @@ struct rcu_state { struct swait_queue_head gp_wq; /* Where GP task waits. */ short gp_flags; /* Commands for GP task. */ short gp_state; /* GP kthread sleep state. */ + unsigned long gp_wake_time; /* Last GP kthread wake. */ + unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ /* End of fields guarded by root rcu_node's lock. */ @@ -328,6 +319,8 @@ struct rcu_state { /* force_quiescent_state(). */ unsigned long gp_start; /* Time at which GP started, */ /* but in jiffies. */ + unsigned long gp_end; /* Time last GP ended, again */ + /* in jiffies. */ unsigned long gp_activity; /* Time of last GP kthread */ /* activity in jiffies. */ unsigned long gp_req_activity; /* Time of last GP request */ @@ -398,26 +391,8 @@ static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; #define RCU_NAME rcu_name #endif /* #else #ifdef CONFIG_TRACING */ -/* - * RCU implementation internal declarations: - */ -extern struct rcu_state rcu_sched_state; - -extern struct rcu_state rcu_bh_state; - -#ifdef CONFIG_PREEMPT_RCU -extern struct rcu_state rcu_preempt_state; -#endif /* #ifdef CONFIG_PREEMPT_RCU */ - int rcu_dynticks_snap(struct rcu_data *rdp); -#ifdef CONFIG_RCU_BOOST -DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); -DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DECLARE_PER_CPU(char, rcu_cpu_has_work); -#endif /* #ifdef CONFIG_RCU_BOOST */ - /* Forward declarations for rcutree_plugin.h */ static void rcu_bootup_announce(void); static void rcu_qs(void); @@ -429,7 +404,7 @@ static void rcu_print_detail_task_stall(void); static int rcu_print_task_stall(struct rcu_node *rnp); static int rcu_print_task_exp_stall(struct rcu_node *rnp); static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); -static void rcu_flavor_check_callbacks(int user); +static void rcu_flavor_sched_clock_irq(int user); void call_rcu(struct rcu_head *head, rcu_callback_t func); static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); @@ -440,7 +415,6 @@ static void __init rcu_spawn_boost_kthreads(void); static void rcu_prepare_kthreads(int cpu); static void rcu_cleanup_after_idle(void); static void rcu_prepare_for_idle(void); -static void rcu_idle_count_callbacks_posted(void); static bool rcu_preempt_has_tasks(struct rcu_node *rnp); static bool rcu_preempt_need_deferred_qs(struct task_struct *t); static void rcu_preempt_deferred_qs(struct task_struct *t); @@ -460,21 +434,14 @@ static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); static void do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); -static void rcu_spawn_all_nocb_kthreads(int cpu); +static void rcu_spawn_cpu_nocb_kthread(int cpu); static void __init rcu_spawn_nocb_kthreads(void); #ifdef CONFIG_RCU_NOCB_CPU static void __init rcu_organize_nocb_kthreads(void); #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ static bool init_nocb_callback_list(struct rcu_data *rdp); +static unsigned long rcu_get_n_cbs_nocb_cpu(struct rcu_data *rdp); static void rcu_bind_gp_kthread(void); static bool rcu_nohz_full_cpu(void); static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); - -#ifdef CONFIG_SRCU -void srcu_online_cpu(unsigned int cpu); -void srcu_offline_cpu(unsigned int cpu); -#else /* #ifdef CONFIG_SRCU */ -void srcu_online_cpu(unsigned int cpu) { } -void srcu_offline_cpu(unsigned int cpu) { } -#endif /* #else #ifdef CONFIG_SRCU */ diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 8d18c1014e2b..4c2a0189e748 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -1,27 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * RCU expedited grace periods * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2016 * - * Authors: Paul E. McKenney <[email protected]> + * Authors: Paul E. McKenney <[email protected]> */ #include <linux/lockdep.h> +static void rcu_exp_handler(void *unused); + /* * Record the start of an expedited grace period. */ @@ -344,7 +333,6 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) { int cpu; unsigned long flags; - smp_call_func_t func; unsigned long mask_ofl_test; unsigned long mask_ofl_ipi; int ret; @@ -352,7 +340,6 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) container_of(wp, struct rcu_exp_work, rew_work); struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); - func = rewp->rew_func; raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Each pass checks a CPU for identity, offline, and idle. */ @@ -396,7 +383,7 @@ retry_ipi: mask_ofl_test |= mask; continue; } - ret = smp_call_function_single(cpu, func, NULL, 0); + ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); if (!ret) { mask_ofl_ipi &= ~mask; continue; @@ -426,7 +413,7 @@ retry_ipi: * Select the nodes that the upcoming expedited grace period needs * to wait for. */ -static void sync_rcu_exp_select_cpus(smp_call_func_t func) +static void sync_rcu_exp_select_cpus(void) { int cpu; struct rcu_node *rnp; @@ -440,7 +427,6 @@ static void sync_rcu_exp_select_cpus(smp_call_func_t func) rnp->exp_need_flush = false; if (!READ_ONCE(rnp->expmask)) continue; /* Avoid early boot non-existent wq. */ - rnp->rew.rew_func = func; if (!READ_ONCE(rcu_par_gp_wq) || rcu_scheduler_active != RCU_SCHEDULER_RUNNING || rcu_is_last_leaf_node(rnp)) { @@ -449,13 +435,13 @@ static void sync_rcu_exp_select_cpus(smp_call_func_t func) continue; } INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); - preempt_disable(); - cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask); + cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1); /* If all offline, queue the work on an unbound CPU. */ - if (unlikely(cpu > rnp->grphi)) + if (unlikely(cpu > rnp->grphi - rnp->grplo)) cpu = WORK_CPU_UNBOUND; + else + cpu += rnp->grplo; queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); - preempt_enable(); rnp->exp_need_flush = true; } @@ -578,10 +564,10 @@ static void rcu_exp_wait_wake(unsigned long s) * Common code to drive an expedited grace period forward, used by * workqueues and mid-boot-time tasks. */ -static void rcu_exp_sel_wait_wake(smp_call_func_t func, unsigned long s) +static void rcu_exp_sel_wait_wake(unsigned long s) { /* Initialize the rcu_node tree in preparation for the wait. */ - sync_rcu_exp_select_cpus(func); + sync_rcu_exp_select_cpus(); /* Wait and clean up, including waking everyone. */ rcu_exp_wait_wake(s); @@ -595,52 +581,7 @@ static void wait_rcu_exp_gp(struct work_struct *wp) struct rcu_exp_work *rewp; rewp = container_of(wp, struct rcu_exp_work, rew_work); - rcu_exp_sel_wait_wake(rewp->rew_func, rewp->rew_s); -} - -/* - * Given a smp_call_function() handler, kick off the specified - * implementation of expedited grace period. - */ -static void _synchronize_rcu_expedited(smp_call_func_t func) -{ - struct rcu_data *rdp; - struct rcu_exp_work rew; - struct rcu_node *rnp; - unsigned long s; - - /* If expedited grace periods are prohibited, fall back to normal. */ - if (rcu_gp_is_normal()) { - wait_rcu_gp(call_rcu); - return; - } - - /* Take a snapshot of the sequence number. */ - s = rcu_exp_gp_seq_snap(); - if (exp_funnel_lock(s)) - return; /* Someone else did our work for us. */ - - /* Ensure that load happens before action based on it. */ - if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { - /* Direct call during scheduler init and early_initcalls(). */ - rcu_exp_sel_wait_wake(func, s); - } else { - /* Marshall arguments & schedule the expedited grace period. */ - rew.rew_func = func; - rew.rew_s = s; - INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); - queue_work(rcu_gp_wq, &rew.rew_work); - } - - /* Wait for expedited grace period to complete. */ - rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); - rnp = rcu_get_root(); - wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], - sync_exp_work_done(s)); - smp_mb(); /* Workqueue actions happen before return. */ - - /* Let the next expedited grace period start. */ - mutex_unlock(&rcu_state.exp_mutex); + rcu_exp_sel_wait_wake(rewp->rew_s); } #ifdef CONFIG_PREEMPT_RCU @@ -652,7 +593,7 @@ static void _synchronize_rcu_expedited(smp_call_func_t func) * ->expmask fields in the rcu_node tree. Otherwise, immediately * report the quiescent state. */ -static void sync_rcu_exp_handler(void *unused) +static void rcu_exp_handler(void *unused) { unsigned long flags; struct rcu_data *rdp = this_cpu_ptr(&rcu_data); @@ -690,9 +631,12 @@ static void sync_rcu_exp_handler(void *unused) */ if (t->rcu_read_lock_nesting > 0) { raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (rnp->expmask & rdp->grpmask) + if (rnp->expmask & rdp->grpmask) { rdp->deferred_qs = true; + WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true); + } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; } /* @@ -726,43 +670,10 @@ static void sync_sched_exp_online_cleanup(int cpu) { } -/** - * synchronize_rcu_expedited - Brute-force RCU grace period - * - * Wait for an RCU-preempt grace period, but expedite it. The basic - * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler - * checks whether the CPU is in an RCU-preempt critical section, and - * if so, it sets a flag that causes the outermost rcu_read_unlock() - * to report the quiescent state. On the other hand, if the CPU is - * not in an RCU read-side critical section, the IPI handler reports - * the quiescent state immediately. - * - * Although this is a greate improvement over previous expedited - * implementations, it is still unfriendly to real-time workloads, so is - * thus not recommended for any sort of common-case code. In fact, if - * you are using synchronize_rcu_expedited() in a loop, please restructure - * your code to batch your updates, and then Use a single synchronize_rcu() - * instead. - * - * This has the same semantics as (but is more brutal than) synchronize_rcu(). - */ -void synchronize_rcu_expedited(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); - - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) - return; - _synchronize_rcu_expedited(sync_rcu_exp_handler); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - #else /* #ifdef CONFIG_PREEMPT_RCU */ /* Invoked on each online non-idle CPU for expedited quiescent state. */ -static void sync_sched_exp_handler(void *unused) +static void rcu_exp_handler(void *unused) { struct rcu_data *rdp; struct rcu_node *rnp; @@ -794,44 +705,78 @@ static void sync_sched_exp_online_cleanup(int cpu) rnp = rdp->mynode; if (!(READ_ONCE(rnp->expmask) & rdp->grpmask)) return; - ret = smp_call_function_single(cpu, sync_sched_exp_handler, NULL, 0); + ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); WARN_ON_ONCE(ret); } -/* - * Because a context switch is a grace period for !PREEMPT, any - * blocking grace-period wait automatically implies a grace period if - * there is only one CPU online at any point time during execution of - * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to - * occasionally incorrectly indicate that there are multiple CPUs online - * when there was in fact only one the whole time, as this just adds some - * overhead: RCU still operates correctly. - */ -static int rcu_blocking_is_gp(void) -{ - int ret; - - might_sleep(); /* Check for RCU read-side critical section. */ - preempt_disable(); - ret = num_online_cpus() <= 1; - preempt_enable(); - return ret; -} +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ -/* PREEMPT=n implementation of synchronize_rcu_expedited(). */ +/** + * synchronize_rcu_expedited - Brute-force RCU grace period + * + * Wait for an RCU grace period, but expedite it. The basic idea is to + * IPI all non-idle non-nohz online CPUs. The IPI handler checks whether + * the CPU is in an RCU critical section, and if so, it sets a flag that + * causes the outermost rcu_read_unlock() to report the quiescent state + * for RCU-preempt or asks the scheduler for help for RCU-sched. On the + * other hand, if the CPU is not in an RCU read-side critical section, + * the IPI handler reports the quiescent state immediately. + * + * Although this is a greate improvement over previous expedited + * implementations, it is still unfriendly to real-time workloads, so is + * thus not recommended for any sort of common-case code. In fact, if + * you are using synchronize_rcu_expedited() in a loop, please restructure + * your code to batch your updates, and then Use a single synchronize_rcu() + * instead. + * + * This has the same semantics as (but is more brutal than) synchronize_rcu(). + */ void synchronize_rcu_expedited(void) { + struct rcu_data *rdp; + struct rcu_exp_work rew; + struct rcu_node *rnp; + unsigned long s; + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); - /* If only one CPU, this is automatically a grace period. */ + /* Is the state is such that the call is a grace period? */ if (rcu_blocking_is_gp()) return; - _synchronize_rcu_expedited(sync_sched_exp_handler); + /* If expedited grace periods are prohibited, fall back to normal. */ + if (rcu_gp_is_normal()) { + wait_rcu_gp(call_rcu); + return; + } + + /* Take a snapshot of the sequence number. */ + s = rcu_exp_gp_seq_snap(); + if (exp_funnel_lock(s)) + return; /* Someone else did our work for us. */ + + /* Ensure that load happens before action based on it. */ + if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { + /* Direct call during scheduler init and early_initcalls(). */ + rcu_exp_sel_wait_wake(s); + } else { + /* Marshall arguments & schedule the expedited grace period. */ + rew.rew_s = s; + INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); + queue_work(rcu_gp_wq, &rew.rew_work); + } + + /* Wait for expedited grace period to complete. */ + rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); + rnp = rcu_get_root(); + wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], + sync_exp_work_done(s)); + smp_mb(); /* Workqueue actions happen before return. */ + + /* Let the next expedited grace period start. */ + mutex_unlock(&rcu_state.exp_mutex); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 05915e536336..97dba50f6fb2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1,27 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions that provide either classic * or preemptible semantics. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright Red Hat, 2009 * Copyright IBM Corporation, 2009 * * Author: Ingo Molnar <[email protected]> - * Paul E. McKenney <[email protected]> + * Paul E. McKenney <[email protected]> */ #include <linux/delay.h> @@ -34,17 +21,7 @@ #include "../time/tick-internal.h" #ifdef CONFIG_RCU_BOOST - #include "../locking/rtmutex_common.h" - -/* - * Control variables for per-CPU and per-rcu_node kthreads. - */ -static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DEFINE_PER_CPU(char, rcu_cpu_has_work); - #else /* #ifdef CONFIG_RCU_BOOST */ /* @@ -307,7 +284,7 @@ static void rcu_qs(void) __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); - barrier(); /* Coordinate with rcu_flavor_check_callbacks(). */ + barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ current->rcu_read_unlock_special.b.need_qs = false; } } @@ -397,6 +374,11 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) return rnp->gp_tasks != NULL; } +/* Bias and limit values for ->rcu_read_lock_nesting. */ +#define RCU_NEST_BIAS INT_MAX +#define RCU_NEST_NMAX (-INT_MAX / 2) +#define RCU_NEST_PMAX (INT_MAX / 2) + /* * Preemptible RCU implementation for rcu_read_lock(). * Just increment ->rcu_read_lock_nesting, shared state will be updated @@ -405,6 +387,8 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) void __rcu_read_lock(void) { current->rcu_read_lock_nesting++; + if (IS_ENABLED(CONFIG_PROVE_LOCKING)) + WARN_ON_ONCE(current->rcu_read_lock_nesting > RCU_NEST_PMAX); barrier(); /* critical section after entry code. */ } EXPORT_SYMBOL_GPL(__rcu_read_lock); @@ -424,20 +408,18 @@ void __rcu_read_unlock(void) --t->rcu_read_lock_nesting; } else { barrier(); /* critical section before exit code. */ - t->rcu_read_lock_nesting = INT_MIN; + t->rcu_read_lock_nesting = -RCU_NEST_BIAS; barrier(); /* assign before ->rcu_read_unlock_special load */ if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) rcu_read_unlock_special(t); barrier(); /* ->rcu_read_unlock_special load before assign */ t->rcu_read_lock_nesting = 0; } -#ifdef CONFIG_PROVE_LOCKING - { - int rrln = READ_ONCE(t->rcu_read_lock_nesting); + if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { + int rrln = t->rcu_read_lock_nesting; - WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); + WARN_ON_ONCE(rrln < 0 && rrln > RCU_NEST_NMAX); } -#endif /* #ifdef CONFIG_PROVE_LOCKING */ } EXPORT_SYMBOL_GPL(__rcu_read_unlock); @@ -597,7 +579,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) */ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) { - return (this_cpu_ptr(&rcu_data)->deferred_qs || + return (__this_cpu_read(rcu_data.deferred_qs) || READ_ONCE(t->rcu_read_unlock_special.s)) && t->rcu_read_lock_nesting <= 0; } @@ -617,11 +599,11 @@ static void rcu_preempt_deferred_qs(struct task_struct *t) if (!rcu_preempt_need_deferred_qs(t)) return; if (couldrecurse) - t->rcu_read_lock_nesting -= INT_MIN; + t->rcu_read_lock_nesting -= RCU_NEST_BIAS; local_irq_save(flags); rcu_preempt_deferred_qs_irqrestore(t, flags); if (couldrecurse) - t->rcu_read_lock_nesting += INT_MIN; + t->rcu_read_lock_nesting += RCU_NEST_BIAS; } /* @@ -642,13 +624,21 @@ static void rcu_read_unlock_special(struct task_struct *t) local_irq_save(flags); irqs_were_disabled = irqs_disabled_flags(flags); - if ((preempt_bh_were_disabled || irqs_were_disabled) && - t->rcu_read_unlock_special.b.blocked) { + if (preempt_bh_were_disabled || irqs_were_disabled) { + WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, false); /* Need to defer quiescent state until everything is enabled. */ - raise_softirq_irqoff(RCU_SOFTIRQ); + if (irqs_were_disabled) { + /* Enabling irqs does not reschedule, so... */ + raise_softirq_irqoff(RCU_SOFTIRQ); + } else { + /* Enabling BH or preempt does reschedule, so... */ + set_tsk_need_resched(current); + set_preempt_need_resched(); + } local_irq_restore(flags); return; } + WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, false); rcu_preempt_deferred_qs_irqrestore(t, flags); } @@ -775,13 +765,13 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) } /* - * Check for a quiescent state from the current CPU. When a task blocks, - * the task is recorded in the corresponding CPU's rcu_node structure, - * which is checked elsewhere. - * - * Caller must disable hard irqs. + * Check for a quiescent state from the current CPU, including voluntary + * context switches for Tasks RCU. When a task blocks, the task is + * recorded in the corresponding CPU's rcu_node structure, which is checked + * elsewhere, hence this function need only check for quiescent states + * related to the current CPU, not to those related to tasks. */ -static void rcu_flavor_check_callbacks(int user) +static void rcu_flavor_sched_clock_irq(int user) { struct task_struct *t = current; @@ -812,54 +802,6 @@ static void rcu_flavor_check_callbacks(int user) t->rcu_read_unlock_special.b.need_qs = true; } -/** - * synchronize_rcu - wait until a grace period has elapsed. - * - * Control will return to the caller some time after a full grace - * period has elapsed, in other words after all currently executing RCU - * read-side critical sections have completed. Note, however, that - * upon return from synchronize_rcu(), the caller might well be executing - * concurrently with new RCU read-side critical sections that began while - * synchronize_rcu() was waiting. RCU read-side critical sections are - * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. - * In addition, regions of code across which interrupts, preemption, or - * softirqs have been disabled also serve as RCU read-side critical - * sections. This includes hardware interrupt handlers, softirq handlers, - * and NMI handlers. - * - * Note that this guarantee implies further memory-ordering guarantees. - * On systems with more than one CPU, when synchronize_rcu() returns, - * each CPU is guaranteed to have executed a full memory barrier since - * the end of its last RCU read-side critical section whose beginning - * preceded the call to synchronize_rcu(). In addition, each CPU having - * an RCU read-side critical section that extends beyond the return from - * synchronize_rcu() is guaranteed to have executed a full memory barrier - * after the beginning of synchronize_rcu() and before the beginning of - * that RCU read-side critical section. Note that these guarantees include - * CPUs that are offline, idle, or executing in user mode, as well as CPUs - * that are executing in the kernel. - * - * Furthermore, if CPU A invoked synchronize_rcu(), which returned - * to its caller on CPU B, then both CPU A and CPU B are guaranteed - * to have executed a full memory barrier during the execution of - * synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but - * again only if the system has more than one CPU). - */ -void synchronize_rcu(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu() in RCU read-side critical section"); - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) - return; - if (rcu_gp_is_expedited()) - synchronize_rcu_expedited(); - else - wait_rcu_gp(call_rcu); -} -EXPORT_SYMBOL_GPL(synchronize_rcu); - /* * Check for a task exiting while in a preemptible-RCU read-side * critical section, clean up if so. No need to issue warnings, @@ -1075,14 +1017,10 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) } /* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. + * Check to see if this CPU is in a non-context-switch quiescent state, + * namely user mode and idle loop. */ -static void rcu_flavor_check_callbacks(int user) +static void rcu_flavor_sched_clock_irq(int user) { if (user || rcu_is_cpu_rrupt_from_idle()) { @@ -1102,22 +1040,6 @@ static void rcu_flavor_check_callbacks(int user) } } -/* PREEMPT=n implementation of synchronize_rcu(). */ -void synchronize_rcu(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu() in RCU read-side critical section"); - if (rcu_blocking_is_gp()) - return; - if (rcu_gp_is_expedited()) - synchronize_rcu_expedited(); - else - wait_rcu_gp(call_rcu); -} -EXPORT_SYMBOL_GPL(synchronize_rcu); - /* * Because preemptible RCU does not exist, tasks cannot possibly exit * while in preemptible RCU read-side critical sections. @@ -1294,11 +1216,11 @@ static void invoke_rcu_callbacks_kthread(void) unsigned long flags; local_irq_save(flags); - __this_cpu_write(rcu_cpu_has_work, 1); - if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && - current != __this_cpu_read(rcu_cpu_kthread_task)) { - rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), - __this_cpu_read(rcu_cpu_kthread_status)); + __this_cpu_write(rcu_data.rcu_cpu_has_work, 1); + if (__this_cpu_read(rcu_data.rcu_cpu_kthread_task) != NULL && + current != __this_cpu_read(rcu_data.rcu_cpu_kthread_task)) { + rcu_wake_cond(__this_cpu_read(rcu_data.rcu_cpu_kthread_task), + __this_cpu_read(rcu_data.rcu_cpu_kthread_status)); } local_irq_restore(flags); } @@ -1309,7 +1231,7 @@ static void invoke_rcu_callbacks_kthread(void) */ static bool rcu_is_callbacks_kthread(void) { - return __this_cpu_read(rcu_cpu_kthread_task) == current; + return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current; } #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) @@ -1356,11 +1278,6 @@ static int rcu_spawn_one_boost_kthread(struct rcu_node *rnp) return 0; } -static void rcu_kthread_do_work(void) -{ - rcu_do_batch(this_cpu_ptr(&rcu_data)); -} - static void rcu_cpu_kthread_setup(unsigned int cpu) { struct sched_param sp; @@ -1371,12 +1288,12 @@ static void rcu_cpu_kthread_setup(unsigned int cpu) static void rcu_cpu_kthread_park(unsigned int cpu) { - per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; + per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; } static int rcu_cpu_kthread_should_run(unsigned int cpu) { - return __this_cpu_read(rcu_cpu_has_work); + return __this_cpu_read(rcu_data.rcu_cpu_has_work); } /* @@ -1386,21 +1303,20 @@ static int rcu_cpu_kthread_should_run(unsigned int cpu) */ static void rcu_cpu_kthread(unsigned int cpu) { - unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); - char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); + unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status); + char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work); int spincnt; for (spincnt = 0; spincnt < 10; spincnt++) { trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); local_bh_disable(); *statusp = RCU_KTHREAD_RUNNING; - this_cpu_inc(rcu_cpu_kthread_loops); local_irq_disable(); work = *workp; *workp = 0; local_irq_enable(); if (work) - rcu_kthread_do_work(); + rcu_do_batch(this_cpu_ptr(&rcu_data)); local_bh_enable(); if (*workp == 0) { trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); @@ -1446,7 +1362,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) } static struct smp_hotplug_thread rcu_cpu_thread_spec = { - .store = &rcu_cpu_kthread_task, + .store = &rcu_data.rcu_cpu_kthread_task, .thread_should_run = rcu_cpu_kthread_should_run, .thread_fn = rcu_cpu_kthread, .thread_comm = "rcuc/%u", @@ -1463,8 +1379,9 @@ static void __init rcu_spawn_boost_kthreads(void) int cpu; for_each_possible_cpu(cpu) - per_cpu(rcu_cpu_has_work, cpu) = 0; - BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); + per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0; + if (WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcub kthread, OOM is now expected behavior\n", __func__)) + return; rcu_for_each_leaf_node(rnp) (void)rcu_spawn_one_boost_kthread(rnp); } @@ -1529,7 +1446,7 @@ static void rcu_prepare_kthreads(int cpu) int rcu_needs_cpu(u64 basemono, u64 *nextevt) { *nextevt = KTIME_MAX; - return rcu_cpu_has_callbacks(NULL); + return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist); } /* @@ -1548,14 +1465,6 @@ static void rcu_prepare_for_idle(void) { } -/* - * Don't bother keeping a running count of the number of RCU callbacks - * posted because CONFIG_RCU_FAST_NO_HZ=n. - */ -static void rcu_idle_count_callbacks_posted(void) -{ -} - #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ /* @@ -1638,11 +1547,8 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) lockdep_assert_irqs_disabled(); - /* Snapshot to detect later posting of non-lazy callback. */ - rdp->nonlazy_posted_snap = rdp->nonlazy_posted; - /* If no callbacks, RCU doesn't need the CPU. */ - if (!rcu_cpu_has_callbacks(&rdp->all_lazy)) { + if (rcu_segcblist_empty(&rdp->cblist)) { *nextevt = KTIME_MAX; return 0; } @@ -1656,11 +1562,12 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) rdp->last_accelerate = jiffies; /* Request timer delay depending on laziness, and round. */ - if (!rdp->all_lazy) { + rdp->all_lazy = !rcu_segcblist_n_nonlazy_cbs(&rdp->cblist); + if (rdp->all_lazy) { + dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; + } else { dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies; - } else { - dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; } *nextevt = basemono + dj * TICK_NSEC; return 0; @@ -1690,7 +1597,7 @@ static void rcu_prepare_for_idle(void) /* Handle nohz enablement switches conservatively. */ tne = READ_ONCE(tick_nohz_active); if (tne != rdp->tick_nohz_enabled_snap) { - if (rcu_cpu_has_callbacks(NULL)) + if (!rcu_segcblist_empty(&rdp->cblist)) invoke_rcu_core(); /* force nohz to see update. */ rdp->tick_nohz_enabled_snap = tne; return; @@ -1703,10 +1610,8 @@ static void rcu_prepare_for_idle(void) * callbacks, invoke RCU core for the side-effect of recalculating * idle duration on re-entry to idle. */ - if (rdp->all_lazy && - rdp->nonlazy_posted != rdp->nonlazy_posted_snap) { + if (rdp->all_lazy && rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)) { rdp->all_lazy = false; - rdp->nonlazy_posted_snap = rdp->nonlazy_posted; invoke_rcu_core(); return; } @@ -1742,19 +1647,6 @@ static void rcu_cleanup_after_idle(void) invoke_rcu_core(); } -/* - * Keep a running count of the number of non-lazy callbacks posted - * on this CPU. This running counter (which is never decremented) allows - * rcu_prepare_for_idle() to detect when something out of the idle loop - * posts a callback, even if an equal number of callbacks are invoked. - * Of course, callbacks should only be posted from within a trace event - * designed to be called from idle or from within RCU_NONIDLE(). - */ -static void rcu_idle_count_callbacks_posted(void) -{ - __this_cpu_add(rcu_data.nonlazy_posted, 1); -} - #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #ifdef CONFIG_RCU_FAST_NO_HZ @@ -1762,13 +1654,12 @@ static void rcu_idle_count_callbacks_posted(void) static void print_cpu_stall_fast_no_hz(char *cp, int cpu) { struct rcu_data *rdp = &per_cpu(rcu_data, cpu); - unsigned long nlpd = rdp->nonlazy_posted - rdp->nonlazy_posted_snap; - sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", + sprintf(cp, "last_accelerate: %04lx/%04lx, Nonlazy posted: %c%c%c", rdp->last_accelerate & 0xffff, jiffies & 0xffff, - ulong2long(nlpd), - rdp->all_lazy ? 'L' : '.', - rdp->tick_nohz_enabled_snap ? '.' : 'D'); + ".l"[rdp->all_lazy], + ".L"[!rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)], + ".D"[!rdp->tick_nohz_enabled_snap]); } #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ @@ -1854,22 +1745,24 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp) /* * Offload callback processing from the boot-time-specified set of CPUs - * specified by rcu_nocb_mask. For each CPU in the set, there is a - * kthread created that pulls the callbacks from the corresponding CPU, - * waits for a grace period to elapse, and invokes the callbacks. - * The no-CBs CPUs do a wake_up() on their kthread when they insert - * a callback into any empty list, unless the rcu_nocb_poll boot parameter - * has been specified, in which case each kthread actively polls its - * CPU. (Which isn't so great for energy efficiency, but which does - * reduce RCU's overhead on that CPU.) + * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads + * created that pull the callbacks from the corresponding CPU, wait for + * a grace period to elapse, and invoke the callbacks. These kthreads + * are organized into leaders, which manage incoming callbacks, wait for + * grace periods, and awaken followers, and the followers, which only + * invoke callbacks. Each leader is its own follower. The no-CBs CPUs + * do a wake_up() on their kthread when they insert a callback into any + * empty list, unless the rcu_nocb_poll boot parameter has been specified, + * in which case each kthread actively polls its CPU. (Which isn't so great + * for energy efficiency, but which does reduce RCU's overhead on that CPU.) * * This is intended to be used in conjunction with Frederic Weisbecker's * adaptive-idle work, which would seriously reduce OS jitter on CPUs * running CPU-bound user-mode computations. * - * Offloading of callback processing could also in theory be used as - * an energy-efficiency measure because CPUs with no RCU callbacks - * queued are more aggressive about entering dyntick-idle mode. + * Offloading of callbacks can also be used as an energy-efficiency + * measure because CPUs with no RCU callbacks queued are more aggressive + * about entering dyntick-idle mode. */ @@ -1973,10 +1866,7 @@ static void wake_nocb_leader_defer(struct rcu_data *rdp, int waketype, raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); } -/* - * Does the specified CPU need an RCU callback for this invocation - * of rcu_barrier()? - */ +/* Does rcu_barrier need to queue an RCU callback on the specified CPU? */ static bool rcu_nocb_cpu_needs_barrier(int cpu) { struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); @@ -1992,12 +1882,12 @@ static bool rcu_nocb_cpu_needs_barrier(int cpu) * callbacks would be posted. In the worst case, the first * barrier in rcu_barrier() suffices (but the caller cannot * necessarily rely on this, not a substitute for the caller - * getting the concurrency design right!). There must also be - * a barrier between the following load an posting of a callback + * getting the concurrency design right!). There must also be a + * barrier between the following load and posting of a callback * (if a callback is in fact needed). This is associated with an * atomic_inc() in the caller. */ - ret = atomic_long_read(&rdp->nocb_q_count); + ret = rcu_get_n_cbs_nocb_cpu(rdp); #ifdef CONFIG_PROVE_RCU rhp = READ_ONCE(rdp->nocb_head); @@ -2052,7 +1942,7 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, TPS("WakeNotPoll")); return; } - len = atomic_long_read(&rdp->nocb_q_count); + len = rcu_get_n_cbs_nocb_cpu(rdp); if (old_rhpp == &rdp->nocb_head) { if (!irqs_disabled_flags(flags)) { /* ... if queue was empty ... */ @@ -2101,11 +1991,11 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, trace_rcu_kfree_callback(rcu_state.name, rhp, (unsigned long)rhp->func, -atomic_long_read(&rdp->nocb_q_count_lazy), - -atomic_long_read(&rdp->nocb_q_count)); + -rcu_get_n_cbs_nocb_cpu(rdp)); else trace_rcu_callback(rcu_state.name, rhp, -atomic_long_read(&rdp->nocb_q_count_lazy), - -atomic_long_read(&rdp->nocb_q_count)); + -rcu_get_n_cbs_nocb_cpu(rdp)); /* * If called from an extended quiescent state with interrupts @@ -2322,13 +2212,14 @@ static int rcu_nocb_kthread(void *arg) tail = rdp->nocb_follower_tail; rdp->nocb_follower_tail = &rdp->nocb_follower_head; raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); - BUG_ON(!list); + if (WARN_ON_ONCE(!list)) + continue; trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeNonEmpty")); /* Each pass through the following loop invokes a callback. */ trace_rcu_batch_start(rcu_state.name, atomic_long_read(&rdp->nocb_q_count_lazy), - atomic_long_read(&rdp->nocb_q_count), -1); + rcu_get_n_cbs_nocb_cpu(rdp), -1); c = cl = 0; while (list) { next = list->next; @@ -2495,15 +2386,16 @@ static void rcu_spawn_one_nocb_kthread(int cpu) /* Spawn the kthread for this CPU. */ t = kthread_run(rcu_nocb_kthread, rdp_spawn, "rcuo%c/%d", rcu_state.abbr, cpu); - BUG_ON(IS_ERR(t)); + if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo kthread, OOM is now expected behavior\n", __func__)) + return; WRITE_ONCE(rdp_spawn->nocb_kthread, t); } /* * If the specified CPU is a no-CBs CPU that does not already have its - * rcuo kthreads, spawn them. + * rcuo kthread, spawn it. */ -static void rcu_spawn_all_nocb_kthreads(int cpu) +static void rcu_spawn_cpu_nocb_kthread(int cpu) { if (rcu_scheduler_fully_active) rcu_spawn_one_nocb_kthread(cpu); @@ -2520,7 +2412,7 @@ static void __init rcu_spawn_nocb_kthreads(void) int cpu; for_each_online_cpu(cpu) - rcu_spawn_all_nocb_kthreads(cpu); + rcu_spawn_cpu_nocb_kthread(cpu); } /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ @@ -2587,6 +2479,26 @@ static bool init_nocb_callback_list(struct rcu_data *rdp) return true; } +/* + * Bind the current task to the offloaded CPUs. If there are no offloaded + * CPUs, leave the task unbound. Splat if the bind attempt fails. + */ +void rcu_bind_current_to_nocb(void) +{ + if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask)) + WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask)); +} +EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb); + +/* + * Return the number of RCU callbacks still queued from the specified + * CPU, which must be a nocbs CPU. + */ +static unsigned long rcu_get_n_cbs_nocb_cpu(struct rcu_data *rdp) +{ + return atomic_long_read(&rdp->nocb_q_count); +} + #else /* #ifdef CONFIG_RCU_NOCB_CPU */ static bool rcu_nocb_cpu_needs_barrier(int cpu) @@ -2634,7 +2546,7 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) { } -static void rcu_spawn_all_nocb_kthreads(int cpu) +static void rcu_spawn_cpu_nocb_kthread(int cpu) { } @@ -2647,6 +2559,11 @@ static bool init_nocb_callback_list(struct rcu_data *rdp) return false; } +static unsigned long rcu_get_n_cbs_nocb_cpu(struct rcu_data *rdp) +{ + return 0; +} + #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ /* diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index f203b94f6b5b..cbaa976c5945 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -1,26 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2001 * * Authors: Dipankar Sarma <[email protected]> * Manfred Spraul <[email protected]> * - * Based on the original work by Paul McKenney <[email protected]> + * Based on the original work by Paul McKenney <[email protected]> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf @@ -52,6 +39,7 @@ #include <linux/tick.h> #include <linux/rcupdate_wait.h> #include <linux/sched/isolation.h> +#include <linux/kprobes.h> #define CREATE_TRACE_POINTS @@ -249,6 +237,7 @@ int notrace debug_lockdep_rcu_enabled(void) current->lockdep_recursion == 0; } EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); +NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled); /** * rcu_read_lock_held() - might we be in RCU read-side critical section? @@ -335,8 +324,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, /* Initialize and register callbacks for each crcu_array element. */ for (i = 0; i < n; i++) { if (checktiny && - (crcu_array[i] == call_rcu || - crcu_array[i] == call_rcu_bh)) { + (crcu_array[i] == call_rcu)) { might_sleep(); continue; } @@ -352,8 +340,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, /* Wait for all callbacks to be invoked. */ for (i = 0; i < n; i++) { if (checktiny && - (crcu_array[i] == call_rcu || - crcu_array[i] == call_rcu_bh)) + (crcu_array[i] == call_rcu)) continue; for (j = 0; j < i; j++) if (crcu_array[j] == crcu_array[i]) @@ -822,7 +809,8 @@ static int __init rcu_spawn_tasks_kthread(void) struct task_struct *t; t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread"); - BUG_ON(IS_ERR(t)); + if (WARN_ONCE(IS_ERR(t), "%s: Could not start Tasks-RCU grace-period kthread, OOM is now expected behavior\n", __func__)) + return 0; smp_mb(); /* Ensure others see full kthread. */ WRITE_ONCE(rcu_tasks_kthread_ptr, t); return 0; |