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-rw-r--r--kernel/fork.c8
-rw-r--r--kernel/futex.c33
-rw-r--r--kernel/sched/Makefile2
-rw-r--r--kernel/sched/auto_group.c6
-rw-r--r--kernel/sched/auto_group.h2
-rw-r--r--kernel/sched/core.c92
-rw-r--r--kernel/sched/cputime.c2
-rw-r--r--kernel/sched/deadline.c2
-rw-r--r--kernel/sched/fair.c276
-rw-r--r--kernel/sched/loadavg.c (renamed from kernel/sched/proc.c)236
-rw-r--r--kernel/sched/rt.c2
-rw-r--r--kernel/sched/sched.h10
-rw-r--r--kernel/sched/stats.h15
-rw-r--r--kernel/sched/wait.c4
-rw-r--r--kernel/signal.c6
-rw-r--r--kernel/time/posix-cpu-timers.c87
16 files changed, 424 insertions, 359 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 03c1eaaa6ef5..0bb88b555550 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1091,10 +1091,7 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
unsigned long cpu_limit;
- /* Thread group counters. */
- thread_group_cputime_init(sig);
-
- cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+ cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
if (cpu_limit != RLIM_INFINITY) {
sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
sig->cputimer.running = 1;
@@ -1396,6 +1393,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->hardirq_context = 0;
p->softirq_context = 0;
#endif
+
+ p->pagefault_disabled = 0;
+
#ifdef CONFIG_LOCKDEP
p->lockdep_depth = 0; /* no locks held yet */
p->curr_chain_key = 0;
diff --git a/kernel/futex.c b/kernel/futex.c
index 2579e407ff67..f9984c363e9a 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1090,9 +1090,11 @@ static void __unqueue_futex(struct futex_q *q)
/*
* The hash bucket lock must be held when this is called.
- * Afterwards, the futex_q must not be accessed.
+ * Afterwards, the futex_q must not be accessed. Callers
+ * must ensure to later call wake_up_q() for the actual
+ * wakeups to occur.
*/
-static void wake_futex(struct futex_q *q)
+static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q)
{
struct task_struct *p = q->task;
@@ -1100,14 +1102,10 @@ static void wake_futex(struct futex_q *q)
return;
/*
- * We set q->lock_ptr = NULL _before_ we wake up the task. If
- * a non-futex wake up happens on another CPU then the task
- * might exit and p would dereference a non-existing task
- * struct. Prevent this by holding a reference on p across the
- * wake up.
+ * Queue the task for later wakeup for after we've released
+ * the hb->lock. wake_q_add() grabs reference to p.
*/
- get_task_struct(p);
-
+ wake_q_add(wake_q, p);
__unqueue_futex(q);
/*
* The waiting task can free the futex_q as soon as
@@ -1117,9 +1115,6 @@ static void wake_futex(struct futex_q *q)
*/
smp_wmb();
q->lock_ptr = NULL;
-
- wake_up_state(p, TASK_NORMAL);
- put_task_struct(p);
}
static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
@@ -1217,6 +1212,7 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
struct futex_q *this, *next;
union futex_key key = FUTEX_KEY_INIT;
int ret;
+ WAKE_Q(wake_q);
if (!bitset)
return -EINVAL;
@@ -1244,13 +1240,14 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
if (!(this->bitset & bitset))
continue;
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
}
spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
out_put_key:
put_futex_key(&key);
out:
@@ -1269,6 +1266,7 @@ futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
struct futex_hash_bucket *hb1, *hb2;
struct futex_q *this, *next;
int ret, op_ret;
+ WAKE_Q(wake_q);
retry:
ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
@@ -1320,7 +1318,7 @@ retry_private:
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
@@ -1334,7 +1332,7 @@ retry_private:
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++op_ret >= nr_wake2)
break;
}
@@ -1344,6 +1342,7 @@ retry_private:
out_unlock:
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
out_put_keys:
put_futex_key(&key2);
out_put_key1:
@@ -1503,6 +1502,7 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
struct futex_pi_state *pi_state = NULL;
struct futex_hash_bucket *hb1, *hb2;
struct futex_q *this, *next;
+ WAKE_Q(wake_q);
if (requeue_pi) {
/*
@@ -1679,7 +1679,7 @@ retry_private:
* woken by futex_unlock_pi().
*/
if (++task_count <= nr_wake && !requeue_pi) {
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
continue;
}
@@ -1719,6 +1719,7 @@ retry_private:
out_unlock:
free_pi_state(pi_state);
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
hb_waiters_dec(hb2);
/*
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 46be87024875..67687973ce80 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -11,7 +11,7 @@ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
endif
-obj-y += core.o proc.o clock.o cputime.o
+obj-y += core.o loadavg.o clock.o cputime.o
obj-y += idle_task.o fair.o rt.o deadline.o stop_task.o
obj-y += wait.o completion.o idle.o
obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index eae160dd669d..750ed601ddf7 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -1,5 +1,3 @@
-#ifdef CONFIG_SCHED_AUTOGROUP
-
#include "sched.h"
#include <linux/proc_fs.h>
@@ -141,7 +139,7 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
p->signal->autogroup = autogroup_kref_get(ag);
- if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
+ if (!READ_ONCE(sysctl_sched_autogroup_enabled))
goto out;
for_each_thread(p, t)
@@ -249,5 +247,3 @@ int autogroup_path(struct task_group *tg, char *buf, int buflen)
return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
}
#endif /* CONFIG_SCHED_DEBUG */
-
-#endif /* CONFIG_SCHED_AUTOGROUP */
diff --git a/kernel/sched/auto_group.h b/kernel/sched/auto_group.h
index 8bd047142816..890c95f2587a 100644
--- a/kernel/sched/auto_group.h
+++ b/kernel/sched/auto_group.h
@@ -29,7 +29,7 @@ extern bool task_wants_autogroup(struct task_struct *p, struct task_group *tg);
static inline struct task_group *
autogroup_task_group(struct task_struct *p, struct task_group *tg)
{
- int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
+ int enabled = READ_ONCE(sysctl_sched_autogroup_enabled);
if (enabled && task_wants_autogroup(p, tg))
return p->signal->autogroup->tg;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 123673291ffb..20b858f2db22 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -511,7 +511,7 @@ static bool set_nr_and_not_polling(struct task_struct *p)
static bool set_nr_if_polling(struct task_struct *p)
{
struct thread_info *ti = task_thread_info(p);
- typeof(ti->flags) old, val = ACCESS_ONCE(ti->flags);
+ typeof(ti->flags) old, val = READ_ONCE(ti->flags);
for (;;) {
if (!(val & _TIF_POLLING_NRFLAG))
@@ -541,6 +541,52 @@ static bool set_nr_if_polling(struct task_struct *p)
#endif
#endif
+void wake_q_add(struct wake_q_head *head, struct task_struct *task)
+{
+ struct wake_q_node *node = &task->wake_q;
+
+ /*
+ * Atomically grab the task, if ->wake_q is !nil already it means
+ * its already queued (either by us or someone else) and will get the
+ * wakeup due to that.
+ *
+ * This cmpxchg() implies a full barrier, which pairs with the write
+ * barrier implied by the wakeup in wake_up_list().
+ */
+ if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
+ return;
+
+ get_task_struct(task);
+
+ /*
+ * The head is context local, there can be no concurrency.
+ */
+ *head->lastp = node;
+ head->lastp = &node->next;
+}
+
+void wake_up_q(struct wake_q_head *head)
+{
+ struct wake_q_node *node = head->first;
+
+ while (node != WAKE_Q_TAIL) {
+ struct task_struct *task;
+
+ task = container_of(node, struct task_struct, wake_q);
+ BUG_ON(!task);
+ /* task can safely be re-inserted now */
+ node = node->next;
+ task->wake_q.next = NULL;
+
+ /*
+ * wake_up_process() implies a wmb() to pair with the queueing
+ * in wake_q_add() so as not to miss wakeups.
+ */
+ wake_up_process(task);
+ put_task_struct(task);
+ }
+}
+
/*
* resched_curr - mark rq's current task 'to be rescheduled now'.
*
@@ -2397,9 +2443,9 @@ unsigned long nr_iowait_cpu(int cpu)
void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
{
- struct rq *this = this_rq();
- *nr_waiters = atomic_read(&this->nr_iowait);
- *load = this->cpu_load[0];
+ struct rq *rq = this_rq();
+ *nr_waiters = atomic_read(&rq->nr_iowait);
+ *load = rq->load.weight;
}
#ifdef CONFIG_SMP
@@ -2497,6 +2543,7 @@ void scheduler_tick(void)
update_rq_clock(rq);
curr->sched_class->task_tick(rq, curr, 0);
update_cpu_load_active(rq);
+ calc_global_load_tick(rq);
raw_spin_unlock(&rq->lock);
perf_event_task_tick();
@@ -2525,7 +2572,7 @@ void scheduler_tick(void)
u64 scheduler_tick_max_deferment(void)
{
struct rq *rq = this_rq();
- unsigned long next, now = ACCESS_ONCE(jiffies);
+ unsigned long next, now = READ_ONCE(jiffies);
next = rq->last_sched_tick + HZ;
@@ -2726,9 +2773,7 @@ again:
* - return from syscall or exception to user-space
* - return from interrupt-handler to user-space
*
- * WARNING: all callers must re-check need_resched() afterward and reschedule
- * accordingly in case an event triggered the need for rescheduling (such as
- * an interrupt waking up a task) while preemption was disabled in __schedule().
+ * WARNING: must be called with preemption disabled!
*/
static void __sched __schedule(void)
{
@@ -2737,7 +2782,6 @@ static void __sched __schedule(void)
struct rq *rq;
int cpu;
- preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
rcu_note_context_switch();
@@ -2801,8 +2845,6 @@ static void __sched __schedule(void)
raw_spin_unlock_irq(&rq->lock);
post_schedule(rq);
-
- sched_preempt_enable_no_resched();
}
static inline void sched_submit_work(struct task_struct *tsk)
@@ -2823,7 +2865,9 @@ asmlinkage __visible void __sched schedule(void)
sched_submit_work(tsk);
do {
+ preempt_disable();
__schedule();
+ sched_preempt_enable_no_resched();
} while (need_resched());
}
EXPORT_SYMBOL(schedule);
@@ -2862,15 +2906,14 @@ void __sched schedule_preempt_disabled(void)
static void __sched notrace preempt_schedule_common(void)
{
do {
- __preempt_count_add(PREEMPT_ACTIVE);
+ preempt_active_enter();
__schedule();
- __preempt_count_sub(PREEMPT_ACTIVE);
+ preempt_active_exit();
/*
* Check again in case we missed a preemption opportunity
* between schedule and now.
*/
- barrier();
} while (need_resched());
}
@@ -2917,7 +2960,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
return;
do {
- __preempt_count_add(PREEMPT_ACTIVE);
+ preempt_active_enter();
/*
* Needs preempt disabled in case user_exit() is traced
* and the tracer calls preempt_enable_notrace() causing
@@ -2927,8 +2970,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
__schedule();
exception_exit(prev_ctx);
- __preempt_count_sub(PREEMPT_ACTIVE);
- barrier();
+ preempt_active_exit();
} while (need_resched());
}
EXPORT_SYMBOL_GPL(preempt_schedule_context);
@@ -2952,17 +2994,11 @@ asmlinkage __visible void __sched preempt_schedule_irq(void)
prev_state = exception_enter();
do {
- __preempt_count_add(PREEMPT_ACTIVE);
+ preempt_active_enter();
local_irq_enable();
__schedule();
local_irq_disable();
- __preempt_count_sub(PREEMPT_ACTIVE);
-
- /*
- * Check again in case we missed a preemption opportunity
- * between schedule and now.
- */
- barrier();
+ preempt_active_exit();
} while (need_resched());
exception_exit(prev_state);
@@ -5314,7 +5350,7 @@ static struct notifier_block migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
-static void __cpuinit set_cpu_rq_start_time(void)
+static void set_cpu_rq_start_time(void)
{
int cpu = smp_processor_id();
struct rq *rq = cpu_rq(cpu);
@@ -7734,11 +7770,11 @@ static long sched_group_rt_runtime(struct task_group *tg)
return rt_runtime_us;
}
-static int sched_group_set_rt_period(struct task_group *tg, long rt_period_us)
+static int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
{
u64 rt_runtime, rt_period;
- rt_period = (u64)rt_period_us * NSEC_PER_USEC;
+ rt_period = rt_period_us * NSEC_PER_USEC;
rt_runtime = tg->rt_bandwidth.rt_runtime;
return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 8394b1ee600c..f5a64ffad176 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -567,7 +567,7 @@ static void cputime_advance(cputime_t *counter, cputime_t new)
{
cputime_t old;
- while (new > (old = ACCESS_ONCE(*counter)))
+ while (new > (old = READ_ONCE(*counter)))
cmpxchg_cputime(counter, old, new);
}
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 5e95145088fd..890ce951c717 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -995,7 +995,7 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
rq = cpu_rq(cpu);
rcu_read_lock();
- curr = ACCESS_ONCE(rq->curr); /* unlocked access */
+ curr = READ_ONCE(rq->curr); /* unlocked access */
/*
* If we are dealing with a -deadline task, we must
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ffeaa4105e48..0d4632f7799b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -141,9 +141,9 @@ static inline void update_load_set(struct load_weight *lw, unsigned long w)
*
* This idea comes from the SD scheduler of Con Kolivas:
*/
-static int get_update_sysctl_factor(void)
+static unsigned int get_update_sysctl_factor(void)
{
- unsigned int cpus = min_t(int, num_online_cpus(), 8);
+ unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
unsigned int factor;
switch (sysctl_sched_tunable_scaling) {
@@ -576,7 +576,7 @@ int sched_proc_update_handler(struct ctl_table *table, int write,
loff_t *ppos)
{
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
- int factor = get_update_sysctl_factor();
+ unsigned int factor = get_update_sysctl_factor();
if (ret || !write)
return ret;
@@ -834,7 +834,7 @@ static unsigned int task_nr_scan_windows(struct task_struct *p)
static unsigned int task_scan_min(struct task_struct *p)
{
- unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size);
+ unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
unsigned int scan, floor;
unsigned int windows = 1;
@@ -1794,7 +1794,12 @@ static void task_numa_placement(struct task_struct *p)
u64 runtime, period;
spinlock_t *group_lock = NULL;
- seq = ACCESS_ONCE(p->mm->numa_scan_seq);
+ /*
+ * The p->mm->numa_scan_seq field gets updated without
+ * exclusive access. Use READ_ONCE() here to ensure
+ * that the field is read in a single access:
+ */
+ seq = READ_ONCE(p->mm->numa_scan_seq);
if (p->numa_scan_seq == seq)
return;
p->numa_scan_seq = seq;
@@ -1938,7 +1943,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
}
rcu_read_lock();
- tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
+ tsk = READ_ONCE(cpu_rq(cpu)->curr);
if (!cpupid_match_pid(tsk, cpupid))
goto no_join;
@@ -2107,7 +2112,15 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
static void reset_ptenuma_scan(struct task_struct *p)
{
- ACCESS_ONCE(p->mm->numa_scan_seq)++;
+ /*
+ * We only did a read acquisition of the mmap sem, so
+ * p->mm->numa_scan_seq is written to without exclusive access
+ * and the update is not guaranteed to be atomic. That's not
+ * much of an issue though, since this is just used for
+ * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
+ * expensive, to avoid any form of compiler optimizations:
+ */
+ WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
p->mm->numa_scan_offset = 0;
}
@@ -4323,6 +4336,189 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
}
#ifdef CONFIG_SMP
+
+/*
+ * per rq 'load' arrray crap; XXX kill this.
+ */
+
+/*
+ * The exact cpuload at various idx values, calculated at every tick would be
+ * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
+ *
+ * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
+ * on nth tick when cpu may be busy, then we have:
+ * load = ((2^idx - 1) / 2^idx)^(n-1) * load
+ * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
+ *
+ * decay_load_missed() below does efficient calculation of
+ * load = ((2^idx - 1) / 2^idx)^(n-1) * load
+ * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
+ *
+ * The calculation is approximated on a 128 point scale.
+ * degrade_zero_ticks is the number of ticks after which load at any
+ * particular idx is approximated to be zero.
+ * degrade_factor is a precomputed table, a row for each load idx.
+ * Each column corresponds to degradation factor for a power of two ticks,
+ * based on 128 point scale.
+ * Example:
+ * row 2, col 3 (=12) says that the degradation at load idx 2 after
+ * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
+ *
+ * With this power of 2 load factors, we can degrade the load n times
+ * by looking at 1 bits in n and doing as many mult/shift instead of
+ * n mult/shifts needed by the exact degradation.
+ */
+#define DEGRADE_SHIFT 7
+static const unsigned char
+ degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
+static const unsigned char
+ degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
+ {0, 0, 0, 0, 0, 0, 0, 0},
+ {64, 32, 8, 0, 0, 0, 0, 0},
+ {96, 72, 40, 12, 1, 0, 0},
+ {112, 98, 75, 43, 15, 1, 0},
+ {120, 112, 98, 76, 45, 16, 2} };
+
+/*
+ * Update cpu_load for any missed ticks, due to tickless idle. The backlog
+ * would be when CPU is idle and so we just decay the old load without
+ * adding any new load.
+ */
+static unsigned long
+decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
+{
+ int j = 0;
+
+ if (!missed_updates)
+ return load;
+
+ if (missed_updates >= degrade_zero_ticks[idx])
+ return 0;
+
+ if (idx == 1)
+ return load >> missed_updates;
+
+ while (missed_updates) {
+ if (missed_updates % 2)
+ load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
+
+ missed_updates >>= 1;
+ j++;
+ }
+ return load;
+}
+
+/*
+ * Update rq->cpu_load[] statistics. This function is usually called every
+ * scheduler tick (TICK_NSEC). With tickless idle this will not be called
+ * every tick. We fix it up based on jiffies.
+ */
+static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
+ unsigned long pending_updates)
+{
+ int i, scale;
+
+ this_rq->nr_load_updates++;
+
+ /* Update our load: */
+ this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
+ for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
+ unsigned long old_load, new_load;
+
+ /* scale is effectively 1 << i now, and >> i divides by scale */
+
+ old_load = this_rq->cpu_load[i];
+ old_load = decay_load_missed(old_load, pending_updates - 1, i);
+ new_load = this_load;
+ /*
+ * Round up the averaging division if load is increasing. This
+ * prevents us from getting stuck on 9 if the load is 10, for
+ * example.
+ */
+ if (new_load > old_load)
+ new_load += scale - 1;
+
+ this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
+ }
+
+ sched_avg_update(this_rq);
+}
+
+#ifdef CONFIG_NO_HZ_COMMON
+/*
+ * There is no sane way to deal with nohz on smp when using jiffies because the
+ * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
+ * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
+ *
+ * Therefore we cannot use the delta approach from the regular tick since that
+ * would seriously skew the load calculation. However we'll make do for those
+ * updates happening while idle (nohz_idle_balance) or coming out of idle
+ * (tick_nohz_idle_exit).
+ *
+ * This means we might still be one tick off for nohz periods.
+ */
+
+/*
+ * Called from nohz_idle_balance() to update the load ratings before doing the
+ * idle balance.
+ */
+static void update_idle_cpu_load(struct rq *this_rq)
+{
+ unsigned long curr_jiffies = READ_ONCE(jiffies);
+ unsigned long load = this_rq->cfs.runnable_load_avg;
+ unsigned long pending_updates;
+
+ /*
+ * bail if there's load or we're actually up-to-date.
+ */
+ if (load || curr_jiffies == this_rq->last_load_update_tick)
+ return;
+
+ pending_updates = curr_jiffies - this_rq->last_load_update_tick;
+ this_rq->last_load_update_tick = curr_jiffies;
+
+ __update_cpu_load(this_rq, load, pending_updates);
+}
+
+/*
+ * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
+ */
+void update_cpu_load_nohz(void)
+{
+ struct rq *this_rq = this_rq();
+ unsigned long curr_jiffies = READ_ONCE(jiffies);
+ unsigned long pending_updates;
+
+ if (curr_jiffies == this_rq->last_load_update_tick)
+ return;
+
+ raw_spin_lock(&this_rq->lock);
+ pending_updates = curr_jiffies - this_rq->last_load_update_tick;
+ if (pending_updates) {
+ this_rq->last_load_update_tick = curr_jiffies;
+ /*
+ * We were idle, this means load 0, the current load might be
+ * !0 due to remote wakeups and the sort.
+ */
+ __update_cpu_load(this_rq, 0, pending_updates);
+ }
+ raw_spin_unlock(&this_rq->lock);
+}
+#endif /* CONFIG_NO_HZ */
+
+/*
+ * Called from scheduler_tick()
+ */
+void update_cpu_load_active(struct rq *this_rq)
+{
+ unsigned long load = this_rq->cfs.runnable_load_avg;
+ /*
+ * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
+ */
+ this_rq->last_load_update_tick = jiffies;
+ __update_cpu_load(this_rq, load, 1);
+}
+
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
@@ -4375,7 +4571,7 @@ static unsigned long capacity_orig_of(int cpu)
static unsigned long cpu_avg_load_per_task(int cpu)
{
struct rq *rq = cpu_rq(cpu);
- unsigned long nr_running = ACCESS_ONCE(rq->cfs.h_nr_running);
+ unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
unsigned long load_avg = rq->cfs.runnable_load_avg;
if (nr_running)
@@ -5467,10 +5663,15 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
}
#ifdef CONFIG_NUMA_BALANCING
-/* Returns true if the destination node has incurred more faults */
+/*
+ * Returns true if the destination node is the preferred node.
+ * Needs to match fbq_classify_rq(): if there is a runnable task
+ * that is not on its preferred node, we should identify it.
+ */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
@@ -5484,29 +5685,30 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is already in the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return false;
-
- /* Task is moving into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return true;
-
- return group_faults(p, dst_nid) > group_faults(p, src_nid);
- }
-
/* Encourage migration to the preferred node. */
if (dst_nid == p->numa_preferred_nid)
return true;
- return task_faults(p, dst_nid) > task_faults(p, src_nid);
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return false;
+
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
+ }
+
+ return dst_faults > src_faults;
}
static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
@@ -5521,23 +5723,23 @@ static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is moving within/into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return false;
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return true;
- /* Task is moving out of the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return true;
+ /* Encourage migration to the preferred node. */
+ if (dst_nid == p->numa_preferred_nid)
+ return false;
- return group_faults(p, dst_nid) < group_faults(p, src_nid);
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
}
- /* Migrating away from the preferred node is always bad. */
- if (src_nid == p->numa_preferred_nid)
- return true;
-
- return task_faults(p, dst_nid) < task_faults(p, src_nid);
+ return dst_faults < src_faults;
}
#else
@@ -6037,8 +6239,8 @@ static unsigned long scale_rt_capacity(int cpu)
* Since we're reading these variables without serialization make sure
* we read them once before doing sanity checks on them.
*/
- age_stamp = ACCESS_ONCE(rq->age_stamp);
- avg = ACCESS_ONCE(rq->rt_avg);
+ age_stamp = READ_ONCE(rq->age_stamp);
+ avg = READ_ONCE(rq->rt_avg);
delta = __rq_clock_broken(rq) - age_stamp;
if (unlikely(delta < 0))
diff --git a/kernel/sched/proc.c b/kernel/sched/loadavg.c
index 8ecd552fe4f2..ef7159012cf3 100644
--- a/kernel/sched/proc.c
+++ b/kernel/sched/loadavg.c
@@ -1,7 +1,9 @@
/*
- * kernel/sched/proc.c
+ * kernel/sched/loadavg.c
*
- * Kernel load calculations, forked from sched/core.c
+ * This file contains the magic bits required to compute the global loadavg
+ * figure. Its a silly number but people think its important. We go through
+ * great pains to make it work on big machines and tickless kernels.
*/
#include <linux/export.h>
@@ -81,7 +83,7 @@ long calc_load_fold_active(struct rq *this_rq)
long nr_active, delta = 0;
nr_active = this_rq->nr_running;
- nr_active += (long) this_rq->nr_uninterruptible;
+ nr_active += (long)this_rq->nr_uninterruptible;
if (nr_active != this_rq->calc_load_active) {
delta = nr_active - this_rq->calc_load_active;
@@ -186,6 +188,7 @@ void calc_load_enter_idle(void)
delta = calc_load_fold_active(this_rq);
if (delta) {
int idx = calc_load_write_idx();
+
atomic_long_add(delta, &calc_load_idle[idx]);
}
}
@@ -241,18 +244,20 @@ fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
{
unsigned long result = 1UL << frac_bits;
- if (n) for (;;) {
- if (n & 1) {
- result *= x;
- result += 1UL << (frac_bits - 1);
- result >>= frac_bits;
+ if (n) {
+ for (;;) {
+ if (n & 1) {
+ result *= x;
+ result += 1UL << (frac_bits - 1);
+ result >>= frac_bits;
+ }
+ n >>= 1;
+ if (!n)
+ break;
+ x *= x;
+ x += 1UL << (frac_bits - 1);
+ x >>= frac_bits;
}
- n >>= 1;
- if (!n)
- break;
- x *= x;
- x += 1UL << (frac_bits - 1);
- x >>= frac_bits;
}
return result;
@@ -285,7 +290,6 @@ static unsigned long
calc_load_n(unsigned long load, unsigned long exp,
unsigned long active, unsigned int n)
{
-
return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
}
@@ -339,6 +343,8 @@ static inline void calc_global_nohz(void) { }
/*
* calc_load - update the avenrun load estimates 10 ticks after the
* CPUs have updated calc_load_tasks.
+ *
+ * Called from the global timer code.
*/
void calc_global_load(unsigned long ticks)
{
@@ -370,10 +376,10 @@ void calc_global_load(unsigned long ticks)
}
/*
- * Called from update_cpu_load() to periodically update this CPU's
+ * Called from scheduler_tick() to periodically update this CPU's
* active count.
*/
-static void calc_load_account_active(struct rq *this_rq)
+void calc_global_load_tick(struct rq *this_rq)
{
long delta;
@@ -386,199 +392,3 @@ static void calc_load_account_active(struct rq *this_rq)
this_rq->calc_load_update += LOAD_FREQ;
}
-
-/*
- * End of global load-average stuff
- */
-
-/*
- * The exact cpuload at various idx values, calculated at every tick would be
- * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
- *
- * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
- * on nth tick when cpu may be busy, then we have:
- * load = ((2^idx - 1) / 2^idx)^(n-1) * load
- * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
- *
- * decay_load_missed() below does efficient calculation of
- * load = ((2^idx - 1) / 2^idx)^(n-1) * load
- * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
- *
- * The calculation is approximated on a 128 point scale.
- * degrade_zero_ticks is the number of ticks after which load at any
- * particular idx is approximated to be zero.
- * degrade_factor is a precomputed table, a row for each load idx.
- * Each column corresponds to degradation factor for a power of two ticks,
- * based on 128 point scale.
- * Example:
- * row 2, col 3 (=12) says that the degradation at load idx 2 after
- * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
- *
- * With this power of 2 load factors, we can degrade the load n times
- * by looking at 1 bits in n and doing as many mult/shift instead of
- * n mult/shifts needed by the exact degradation.
- */
-#define DEGRADE_SHIFT 7
-static const unsigned char
- degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
-static const unsigned char
- degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
- {0, 0, 0, 0, 0, 0, 0, 0},
- {64, 32, 8, 0, 0, 0, 0, 0},
- {96, 72, 40, 12, 1, 0, 0},
- {112, 98, 75, 43, 15, 1, 0},
- {120, 112, 98, 76, 45, 16, 2} };
-
-/*
- * Update cpu_load for any missed ticks, due to tickless idle. The backlog
- * would be when CPU is idle and so we just decay the old load without
- * adding any new load.
- */
-static unsigned long
-decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
-{
- int j = 0;
-
- if (!missed_updates)
- return load;
-
- if (missed_updates >= degrade_zero_ticks[idx])
- return 0;
-
- if (idx == 1)
- return load >> missed_updates;
-
- while (missed_updates) {
- if (missed_updates % 2)
- load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
-
- missed_updates >>= 1;
- j++;
- }
- return load;
-}
-
-/*
- * Update rq->cpu_load[] statistics. This function is usually called every
- * scheduler tick (TICK_NSEC). With tickless idle this will not be called
- * every tick. We fix it up based on jiffies.
- */
-static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
- unsigned long pending_updates)
-{
- int i, scale;
-
- this_rq->nr_load_updates++;
-
- /* Update our load: */
- this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
- for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
- unsigned long old_load, new_load;
-
- /* scale is effectively 1 << i now, and >> i divides by scale */
-
- old_load = this_rq->cpu_load[i];
- old_load = decay_load_missed(old_load, pending_updates - 1, i);
- new_load = this_load;
- /*
- * Round up the averaging division if load is increasing. This
- * prevents us from getting stuck on 9 if the load is 10, for
- * example.
- */
- if (new_load > old_load)
- new_load += scale - 1;
-
- this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
- }
-
- sched_avg_update(this_rq);
-}
-
-#ifdef CONFIG_SMP
-static inline unsigned long get_rq_runnable_load(struct rq *rq)
-{
- return rq->cfs.runnable_load_avg;
-}
-#else
-static inline unsigned long get_rq_runnable_load(struct rq *rq)
-{
- return rq->load.weight;
-}
-#endif
-
-#ifdef CONFIG_NO_HZ_COMMON
-/*
- * There is no sane way to deal with nohz on smp when using jiffies because the
- * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
- * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
- *
- * Therefore we cannot use the delta approach from the regular tick since that
- * would seriously skew the load calculation. However we'll make do for those
- * updates happening while idle (nohz_idle_balance) or coming out of idle
- * (tick_nohz_idle_exit).
- *
- * This means we might still be one tick off for nohz periods.
- */
-
-/*
- * Called from nohz_idle_balance() to update the load ratings before doing the
- * idle balance.
- */
-void update_idle_cpu_load(struct rq *this_rq)
-{
- unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
- unsigned long load = get_rq_runnable_load(this_rq);
- unsigned long pending_updates;
-
- /*
- * bail if there's load or we're actually up-to-date.
- */
- if (load || curr_jiffies == this_rq->last_load_update_tick)
- return;
-
- pending_updates = curr_jiffies - this_rq->last_load_update_tick;
- this_rq->last_load_update_tick = curr_jiffies;
-
- __update_cpu_load(this_rq, load, pending_updates);
-}
-
-/*
- * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
- */
-void update_cpu_load_nohz(void)
-{
- struct rq *this_rq = this_rq();
- unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
- unsigned long pending_updates;
-
- if (curr_jiffies == this_rq->last_load_update_tick)
- return;
-
- raw_spin_lock(&this_rq->lock);
- pending_updates = curr_jiffies - this_rq->last_load_update_tick;
- if (pending_updates) {
- this_rq->last_load_update_tick = curr_jiffies;
- /*
- * We were idle, this means load 0, the current load might be
- * !0 due to remote wakeups and the sort.
- */
- __update_cpu_load(this_rq, 0, pending_updates);
- }
- raw_spin_unlock(&this_rq->lock);
-}
-#endif /* CONFIG_NO_HZ */
-
-/*
- * Called from scheduler_tick()
- */
-void update_cpu_load_active(struct rq *this_rq)
-{
- unsigned long load = get_rq_runnable_load(this_rq);
- /*
- * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
- */
- this_rq->last_load_update_tick = jiffies;
- __update_cpu_load(this_rq, load, 1);
-
- calc_load_account_active(this_rq);
-}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 575da76a3874..560d2fa623c3 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1323,7 +1323,7 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
rq = cpu_rq(cpu);
rcu_read_lock();
- curr = ACCESS_ONCE(rq->curr); /* unlocked access */
+ curr = READ_ONCE(rq->curr); /* unlocked access */
/*
* If the current task on @p's runqueue is an RT task, then
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e0e129993958..d85455539d5c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -26,8 +26,14 @@ extern __read_mostly int scheduler_running;
extern unsigned long calc_load_update;
extern atomic_long_t calc_load_tasks;
+extern void calc_global_load_tick(struct rq *this_rq);
extern long calc_load_fold_active(struct rq *this_rq);
+
+#ifdef CONFIG_SMP
extern void update_cpu_load_active(struct rq *this_rq);
+#else
+static inline void update_cpu_load_active(struct rq *this_rq) { }
+#endif
/*
* Helpers for converting nanosecond timing to jiffy resolution
@@ -707,7 +713,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
static inline u64 __rq_clock_broken(struct rq *rq)
{
- return ACCESS_ONCE(rq->clock);
+ return READ_ONCE(rq->clock);
}
static inline u64 rq_clock(struct rq *rq)
@@ -1298,8 +1304,6 @@ extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
unsigned long to_ratio(u64 period, u64 runtime);
-extern void update_idle_cpu_load(struct rq *this_rq);
-
extern void init_task_runnable_average(struct task_struct *p);
static inline void add_nr_running(struct rq *rq, unsigned count)
diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 4ab704339656..077ebbd5e10f 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -174,7 +174,8 @@ static inline bool cputimer_running(struct task_struct *tsk)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
- if (!cputimer->running)
+ /* Check if cputimer isn't running. This is accessed without locking. */
+ if (!READ_ONCE(cputimer->running))
return false;
/*
@@ -215,9 +216,7 @@ static inline void account_group_user_time(struct task_struct *tsk,
if (!cputimer_running(tsk))
return;
- raw_spin_lock(&cputimer->lock);
- cputimer->cputime.utime += cputime;
- raw_spin_unlock(&cputimer->lock);
+ atomic64_add(cputime, &cputimer->cputime_atomic.utime);
}
/**
@@ -238,9 +237,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
if (!cputimer_running(tsk))
return;
- raw_spin_lock(&cputimer->lock);
- cputimer->cputime.stime += cputime;
- raw_spin_unlock(&cputimer->lock);
+ atomic64_add(cputime, &cputimer->cputime_atomic.stime);
}
/**
@@ -261,7 +258,5 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
if (!cputimer_running(tsk))
return;
- raw_spin_lock(&cputimer->lock);
- cputimer->cputime.sum_exec_runtime += ns;
- raw_spin_unlock(&cputimer->lock);
+ atomic64_add(ns, &cputimer->cputime_atomic.sum_exec_runtime);
}
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 852143a79f36..2ccec988d6b7 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -601,7 +601,7 @@ EXPORT_SYMBOL(bit_wait_io);
__sched int bit_wait_timeout(struct wait_bit_key *word)
{
- unsigned long now = ACCESS_ONCE(jiffies);
+ unsigned long now = READ_ONCE(jiffies);
if (signal_pending_state(current->state, current))
return 1;
if (time_after_eq(now, word->timeout))
@@ -613,7 +613,7 @@ EXPORT_SYMBOL_GPL(bit_wait_timeout);
__sched int bit_wait_io_timeout(struct wait_bit_key *word)
{
- unsigned long now = ACCESS_ONCE(jiffies);
+ unsigned long now = READ_ONCE(jiffies);
if (signal_pending_state(current->state, current))
return 1;
if (time_after_eq(now, word->timeout))
diff --git a/kernel/signal.c b/kernel/signal.c
index d51c5ddd855c..f19833b5db3c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -245,7 +245,7 @@ static inline void print_dropped_signal(int sig)
* RETURNS:
* %true if @mask is set, %false if made noop because @task was dying.
*/
-bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask)
+bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
{
BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
@@ -297,7 +297,7 @@ void task_clear_jobctl_trapping(struct task_struct *task)
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
-void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask)
+void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
{
BUG_ON(mask & ~JOBCTL_PENDING_MASK);
@@ -2000,7 +2000,7 @@ static bool do_signal_stop(int signr)
struct signal_struct *sig = current->signal;
if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
- unsigned int gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
+ unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
struct task_struct *t;
/* signr will be recorded in task->jobctl for retries */
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 0075da74abf0..892e3dae0aac 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -196,39 +196,62 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
return 0;
}
-static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
+/*
+ * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
+ * to avoid race conditions with concurrent updates to cputime.
+ */
+static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
{
- if (b->utime > a->utime)
- a->utime = b->utime;
+ u64 curr_cputime;
+retry:
+ curr_cputime = atomic64_read(cputime);
+ if (sum_cputime > curr_cputime) {
+ if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
+ goto retry;
+ }
+}
- if (b->stime > a->stime)
- a->stime = b->stime;
+static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)
+{
+ __update_gt_cputime(&cputime_atomic->utime, sum->utime);
+ __update_gt_cputime(&cputime_atomic->stime, sum->stime);
+ __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
+}
- if (b->sum_exec_runtime > a->sum_exec_runtime)
- a->sum_exec_runtime = b->sum_exec_runtime;
+/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */
+static inline void sample_cputime_atomic(struct task_cputime *times,
+ struct task_cputime_atomic *atomic_times)
+{
+ times->utime = atomic64_read(&atomic_times->utime);
+ times->stime = atomic64_read(&atomic_times->stime);
+ times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
}
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct task_cputime sum;
- unsigned long flags;
- if (!cputimer->running) {
+ /* Check if cputimer isn't running. This is accessed without locking. */
+ if (!READ_ONCE(cputimer->running)) {
/*
* The POSIX timer interface allows for absolute time expiry
* values through the TIMER_ABSTIME flag, therefore we have
- * to synchronize the timer to the clock every time we start
- * it.
+ * to synchronize the timer to the clock every time we start it.
*/
thread_group_cputime(tsk, &sum);
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- cputimer->running = 1;
- update_gt_cputime(&cputimer->cputime, &sum);
- } else
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- *times = cputimer->cputime;
- raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+ update_gt_cputime(&cputimer->cputime_atomic, &sum);
+
+ /*
+ * We're setting cputimer->running without a lock. Ensure
+ * this only gets written to in one operation. We set
+ * running after update_gt_cputime() as a small optimization,
+ * but barriers are not required because update_gt_cputime()
+ * can handle concurrent updates.
+ */
+ WRITE_ONCE(cputimer->running, 1);
+ }
+ sample_cputime_atomic(times, &cputimer->cputime_atomic);
}
/*
@@ -582,7 +605,8 @@ bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
if (!task_cputime_zero(&tsk->cputime_expires))
return false;
- if (tsk->signal->cputimer.running)
+ /* Check if cputimer is running. This is accessed without locking. */
+ if (READ_ONCE(tsk->signal->cputimer.running))
return false;
return true;
@@ -852,10 +876,10 @@ static void check_thread_timers(struct task_struct *tsk,
/*
* Check for the special case thread timers.
*/
- soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
+ soft = READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long hard =
- ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
+ READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
if (hard != RLIM_INFINITY &&
tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
@@ -882,14 +906,12 @@ static void check_thread_timers(struct task_struct *tsk,
}
}
-static void stop_process_timers(struct signal_struct *sig)
+static inline void stop_process_timers(struct signal_struct *sig)
{
struct thread_group_cputimer *cputimer = &sig->cputimer;
- unsigned long flags;
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- cputimer->running = 0;
- raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+ /* Turn off cputimer->running. This is done without locking. */
+ WRITE_ONCE(cputimer->running, 0);
}
static u32 onecputick;
@@ -958,11 +980,11 @@ static void check_process_timers(struct task_struct *tsk,
SIGPROF);
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
SIGVTALRM);
- soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+ soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long psecs = cputime_to_secs(ptime);
unsigned long hard =
- ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
+ READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
cputime_t x;
if (psecs >= hard) {
/*
@@ -1111,12 +1133,11 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
}
sig = tsk->signal;
- if (sig->cputimer.running) {
+ /* Check if cputimer is running. This is accessed without locking. */
+ if (READ_ONCE(sig->cputimer.running)) {
struct task_cputime group_sample;
- raw_spin_lock(&sig->cputimer.lock);
- group_sample = sig->cputimer.cputime;
- raw_spin_unlock(&sig->cputimer.lock);
+ sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);
if (task_cputime_expired(&group_sample, &sig->cputime_expires))
return 1;
@@ -1157,7 +1178,7 @@ void run_posix_cpu_timers(struct task_struct *tsk)
* If there are any active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) cputimer must be running.
*/
- if (tsk->signal->cputimer.running)
+ if (READ_ONCE(tsk->signal->cputimer.running))
check_process_timers(tsk, &firing);
/*
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