Merge tag 'rcu.release.v6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Neeraj Upadhyay:
 "Context tracking:
   - rename context tracking state related symbols and remove references
     to "dynticks" in various context tracking state variables and
     related helpers
   - force context_tracking_enabled_this_cpu() to be inlined to avoid
     leaving a noinstr section

  CSD lock:
   - enhance CSD-lock diagnostic reports
   - add an API to provide an indication of ongoing CSD-lock stall

  nocb:
   - update and simplify RCU nocb code to handle (de-)offloading of
     callbacks only for offline CPUs
   - fix RT throttling hrtimer being armed from offline CPU

  rcutorture:
   - remove redundant rcu_torture_ops get_gp_completed fields
   - add SRCU ->same_gp_state and ->get_comp_state functions
   - add generic test for NUM_ACTIVE_*RCU_POLL* for testing RCU and SRCU
     polled grace periods
   - add CFcommon.arch for arch-specific Kconfig options
   - print number of update types in rcu_torture_write_types()
   - add rcutree.nohz_full_patience_delay testing to the TREE07 scenario
   - add a stall_cpu_repeat module parameter to test repeated CPU stalls
   - add argument to limit number of CPUs a guest OS can use in
     torture.sh

  rcustall:
   - abbreviate RCU CPU stall warnings during CSD-lock stalls
   - Allow dump_cpu_task() to be called without disabling preemption
   - defer printing stall-warning backtrace when holding rcu_node lock

  srcu:
   - make SRCU gp seq wrap-around faster
   - add KCSAN checks for concurrent updates to ->srcu_n_exp_nodelay and
     ->reschedule_count which are used in heuristics governing
     auto-expediting of normal SRCU grace periods and
     grace-period-state-machine delays
   - mark idle SRCU-barrier callbacks to help identify stuck
     SRCU-barrier callback

  rcu tasks:
   - remove RCU Tasks Rude asynchronous APIs as they are no longer used
   - stop testing RCU Tasks Rude asynchronous APIs
   - fix access to non-existent percpu regions
   - check processor-ID assumptions during chosen CPU calculation for
     callback enqueuing
   - update description of rtp->tasks_gp_seq grace-period sequence
     number
   - add rcu_barrier_cb_is_done() to identify whether a given
     rcu_barrier callback is stuck
   - mark idle Tasks-RCU-barrier callbacks
   - add *torture_stats_print() functions to print detailed diagnostics
     for Tasks-RCU variants
   - capture start time of rcu_barrier_tasks*() operation to help
     distinguish a hung barrier operation from a long series of barrier
     operations

  refscale:
   - add a TINY scenario to support tests of Tiny RCU and Tiny
     SRCU
   - optimize process_durations() operation

  rcuscale:
   - dump stacks of stalled rcu_scale_writer() instances and
     grace-period statistics when rcu_scale_writer() stalls
   - mark idle RCU-barrier callbacks to identify stuck RCU-barrier
     callbacks
   - print detailed grace-period and barrier diagnostics on
     rcu_scale_writer() hangs for Tasks-RCU variants
   - warn if async module parameter is specified for RCU implementations
     that do not have async primitives such as RCU Tasks Rude
   - make all writer tasks report upon hang
   - tolerate repeated GFP_KERNEL failure in rcu_scale_writer()
   - use special allocator for rcu_scale_writer()
   - NULL out top-level pointers to heap memory to avoid double-free
     bugs on modprobe failures
   - maintain per-task instead of per-CPU callbacks count to avoid any
     issues with migration of either tasks or callbacks
   - constify struct ref_scale_ops

  Fixes:
   - use system_unbound_wq for kfree_rcu work to avoid disturbing
     isolated CPUs

  Misc:
   - warn on unexpected rcu_state.srs_done_tail state
   - better define "atomic" for list_replace_rcu() and
     hlist_replace_rcu() routines
   - annotate struct kvfree_rcu_bulk_data with __counted_by()"

* tag 'rcu.release.v6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (90 commits)
  rcu: Defer printing stall-warning backtrace when holding rcu_node lock
  rcu/nocb: Remove superfluous memory barrier after bypass enqueue
  rcu/nocb: Conditionally wake up rcuo if not already waiting on GP
  rcu/nocb: Fix RT throttling hrtimer armed from offline CPU
  rcu/nocb: Simplify (de-)offloading state machine
  context_tracking: Tag context_tracking_enabled_this_cpu() __always_inline
  context_tracking, rcu: Rename rcu_dyntick trace event into rcu_watching
  rcu: Update stray documentation references to rcu_dynticks_eqs_{enter, exit}()
  rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()
  rcu: Rename rcu_implicit_dynticks_qs() into rcu_watching_snap_recheck()
  rcu: Rename dyntick_save_progress_counter() into rcu_watching_snap_save()
  rcu: Rename struct rcu_data .exp_dynticks_snap into .exp_watching_snap
  rcu: Rename struct rcu_data .dynticks_snap into .watching_snap
  rcu: Rename rcu_dynticks_zero_in_eqs() into rcu_watching_zero_in_eqs()
  rcu: Rename rcu_dynticks_in_eqs_since() into rcu_watching_snap_stopped_since()
  rcu: Rename rcu_dynticks_in_eqs() into rcu_watching_snap_in_eqs()
  rcu: Rename rcu_dynticks_eqs_online() into rcu_watching_online()
  context_tracking, rcu: Rename rcu_dynticks_curr_cpu_in_eqs() into rcu_is_watching_curr_cpu()
  context_tracking, rcu: Rename rcu_dynticks_task*() into rcu_task*()
  refscale: Constify struct ref_scale_ops
  ...

1 files changed, 35 insertions, 32 deletions

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index f4ea5b1ec068..0db9db73f57f 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -28,6 +28,7 @@
 #include <linux/rcupdate_trace.h>
 #include <linux/reboot.h>
 #include <linux/sched.h>
+#include <linux/seq_buf.h>
 #include <linux/spinlock.h>
 #include <linux/smp.h>
 #include <linux/stat.h>
@@ -134,7 +135,7 @@ struct ref_scale_ops {
 	const char *name;
 };
 
-static struct ref_scale_ops *cur_ops;
+static const struct ref_scale_ops *cur_ops;
 
 static void un_delay(const int udl, const int ndl)
 {
@@ -170,7 +171,7 @@ static bool rcu_sync_scale_init(void)
 	return true;
 }
 
-static struct ref_scale_ops rcu_ops = {
+static const struct ref_scale_ops rcu_ops = {
 	.init		= rcu_sync_scale_init,
 	.readsection	= ref_rcu_read_section,
 	.delaysection	= ref_rcu_delay_section,
@@ -204,7 +205,7 @@ static void srcu_ref_scale_delay_section(const int nloops, const int udl, const
 	}
 }
 
-static struct ref_scale_ops srcu_ops = {
+static const struct ref_scale_ops srcu_ops = {
 	.init		= rcu_sync_scale_init,
 	.readsection	= srcu_ref_scale_read_section,
 	.delaysection	= srcu_ref_scale_delay_section,
@@ -231,7 +232,7 @@ static void rcu_tasks_ref_scale_delay_section(const int nloops, const int udl, c
 		un_delay(udl, ndl);
 }
 
-static struct ref_scale_ops rcu_tasks_ops = {
+static const struct ref_scale_ops rcu_tasks_ops = {
 	.init		= rcu_sync_scale_init,
 	.readsection	= rcu_tasks_ref_scale_read_section,
 	.delaysection	= rcu_tasks_ref_scale_delay_section,
@@ -270,7 +271,7 @@ static void rcu_trace_ref_scale_delay_section(const int nloops, const int udl, c
 	}
 }
 
-static struct ref_scale_ops rcu_trace_ops = {
+static const struct ref_scale_ops rcu_trace_ops = {
 	.init		= rcu_sync_scale_init,
 	.readsection	= rcu_trace_ref_scale_read_section,
 	.delaysection	= rcu_trace_ref_scale_delay_section,
@@ -309,7 +310,7 @@ static void ref_refcnt_delay_section(const int nloops, const int udl, const int
 	}
 }
 
-static struct ref_scale_ops refcnt_ops = {
+static const struct ref_scale_ops refcnt_ops = {
 	.init		= rcu_sync_scale_init,
 	.readsection	= ref_refcnt_section,
 	.delaysection	= ref_refcnt_delay_section,
@@ -346,7 +347,7 @@ static void ref_rwlock_delay_section(const int nloops, const int udl, const int
 	}
 }
 
-static struct ref_scale_ops rwlock_ops = {
+static const struct ref_scale_ops rwlock_ops = {
 	.init		= ref_rwlock_init,
 	.readsection	= ref_rwlock_section,
 	.delaysection	= ref_rwlock_delay_section,
@@ -383,7 +384,7 @@ static void ref_rwsem_delay_section(const int nloops, const int udl, const int n
 	}
 }
 
-static struct ref_scale_ops rwsem_ops = {
+static const struct ref_scale_ops rwsem_ops = {
 	.init		= ref_rwsem_init,
 	.readsection	= ref_rwsem_section,
 	.delaysection	= ref_rwsem_delay_section,
@@ -418,7 +419,7 @@ static void ref_lock_delay_section(const int nloops, const int udl, const int nd
 	preempt_enable();
 }
 
-static struct ref_scale_ops lock_ops = {
+static const struct ref_scale_ops lock_ops = {
 	.readsection	= ref_lock_section,
 	.delaysection	= ref_lock_delay_section,
 	.name		= "lock"
@@ -453,7 +454,7 @@ static void ref_lock_irq_delay_section(const int nloops, const int udl, const in
 	preempt_enable();
 }
 
-static struct ref_scale_ops lock_irq_ops = {
+static const struct ref_scale_ops lock_irq_ops = {
 	.readsection	= ref_lock_irq_section,
 	.delaysection	= ref_lock_irq_delay_section,
 	.name		= "lock-irq"
@@ -489,7 +490,7 @@ static void ref_acqrel_delay_section(const int nloops, const int udl, const int
 	preempt_enable();
 }
 
-static struct ref_scale_ops acqrel_ops = {
+static const struct ref_scale_ops acqrel_ops = {
 	.readsection	= ref_acqrel_section,
 	.delaysection	= ref_acqrel_delay_section,
 	.name		= "acqrel"
@@ -523,7 +524,7 @@ static void ref_clock_delay_section(const int nloops, const int udl, const int n
 	stopopts = x;
 }
 
-static struct ref_scale_ops clock_ops = {
+static const struct ref_scale_ops clock_ops = {
 	.readsection	= ref_clock_section,
 	.delaysection	= ref_clock_delay_section,
 	.name		= "clock"
@@ -555,7 +556,7 @@ static void ref_jiffies_delay_section(const int nloops, const int udl, const int
 	stopopts = x;
 }
 
-static struct ref_scale_ops jiffies_ops = {
+static const struct ref_scale_ops jiffies_ops = {
 	.readsection	= ref_jiffies_section,
 	.delaysection	= ref_jiffies_delay_section,
 	.name		= "jiffies"
@@ -705,9 +706,9 @@ static void refscale_typesafe_ctor(void *rtsp_in)
 	preempt_enable();
 }
 
-static struct ref_scale_ops typesafe_ref_ops;
-static struct ref_scale_ops typesafe_lock_ops;
-static struct ref_scale_ops typesafe_seqlock_ops;
+static const struct ref_scale_ops typesafe_ref_ops;
+static const struct ref_scale_ops typesafe_lock_ops;
+static const struct ref_scale_ops typesafe_seqlock_ops;
 
 // Initialize for a typesafe test.
 static bool typesafe_init(void)
@@ -768,7 +769,7 @@ static void typesafe_cleanup(void)
 }
 
 // The typesafe_init() function distinguishes these structures by address.
-static struct ref_scale_ops typesafe_ref_ops = {
+static const struct ref_scale_ops typesafe_ref_ops = {
 	.init		= typesafe_init,
 	.cleanup	= typesafe_cleanup,
 	.readsection	= typesafe_read_section,
@@ -776,7 +777,7 @@ static struct ref_scale_ops typesafe_ref_ops = {
 	.name		= "typesafe_ref"
 };
 
-static struct ref_scale_ops typesafe_lock_ops = {
+static const struct ref_scale_ops typesafe_lock_ops = {
 	.init		= typesafe_init,
 	.cleanup	= typesafe_cleanup,
 	.readsection	= typesafe_read_section,
@@ -784,7 +785,7 @@ static struct ref_scale_ops typesafe_lock_ops = {
 	.name		= "typesafe_lock"
 };
 
-static struct ref_scale_ops typesafe_seqlock_ops = {
+static const struct ref_scale_ops typesafe_seqlock_ops = {
 	.init		= typesafe_init,
 	.cleanup	= typesafe_cleanup,
 	.readsection	= typesafe_read_section,
@@ -891,32 +892,34 @@ static u64 process_durations(int n)
 {
 	int i;
 	struct reader_task *rt;
-	char buf1[64];
+	struct seq_buf s;
 	char *buf;
 	u64 sum = 0;
 
 	buf = kmalloc(800 + 64, GFP_KERNEL);
 	if (!buf)
 		return 0;
-	buf[0] = 0;
-	sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
-		exp_idx);
+	seq_buf_init(&s, buf, 800 + 64);
+
+	seq_buf_printf(&s, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
+		       exp_idx);
 
 	for (i = 0; i < n && !torture_must_stop(); i++) {
 		rt = &(reader_tasks[i]);
-		sprintf(buf1, "%d: %llu\t", i, rt->last_duration_ns);
 
 		if (i % 5 == 0)
-			strcat(buf, "\n");
-		if (strlen(buf) >= 800) {
-			pr_alert("%s", buf);
-			buf[0] = 0;
+			seq_buf_putc(&s, '\n');
+
+		if (seq_buf_used(&s) >= 800) {
+			pr_alert("%s", seq_buf_str(&s));
+			seq_buf_clear(&s);
 		}
-		strcat(buf, buf1);
+
+		seq_buf_printf(&s, "%d: %llu\t", i, rt->last_duration_ns);
 
 		sum += rt->last_duration_ns;
 	}
-	pr_alert("%s\n", buf);
+	pr_alert("%s\n", seq_buf_str(&s));
 
 	kfree(buf);
 	return sum;
@@ -1023,7 +1026,7 @@ end:
 }
 
 static void
-ref_scale_print_module_parms(struct ref_scale_ops *cur_ops, const char *tag)
+ref_scale_print_module_parms(const struct ref_scale_ops *cur_ops, const char *tag)
 {
 	pr_alert("%s" SCALE_FLAG
 		 "--- %s:  verbose=%d verbose_batched=%d shutdown=%d holdoff=%d lookup_instances=%ld loops=%ld nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
@@ -1078,7 +1081,7 @@ ref_scale_init(void)
 {
 	long i;
 	int firsterr = 0;
-	static struct ref_scale_ops *scale_ops[] = {
+	static const struct ref_scale_ops *scale_ops[] = {
 		&rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
 		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops,
 		&typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,