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-rw-r--r--kernel/time/posix-cpu-timers.c81
-rw-r--r--kernel/time/posix-timers.c4
-rw-r--r--kernel/time/tick-common.c12
-rw-r--r--kernel/time/tick-sched.c135
-rw-r--r--kernel/time/tick-sched.h67
5 files changed, 187 insertions, 112 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 2f5e9b34022c..e9c6f9d0e42c 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -846,6 +846,8 @@ static u64 collect_timerqueue(struct timerqueue_head *head,
return expires;
ctmr->firing = 1;
+ /* See posix_cpu_timer_wait_running() */
+ rcu_assign_pointer(ctmr->handling, current);
cpu_timer_dequeue(ctmr);
list_add_tail(&ctmr->elist, firing);
}
@@ -1161,7 +1163,49 @@ static void handle_posix_cpu_timers(struct task_struct *tsk);
#ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
static void posix_cpu_timers_work(struct callback_head *work)
{
+ struct posix_cputimers_work *cw = container_of(work, typeof(*cw), work);
+
+ mutex_lock(&cw->mutex);
handle_posix_cpu_timers(current);
+ mutex_unlock(&cw->mutex);
+}
+
+/*
+ * Invoked from the posix-timer core when a cancel operation failed because
+ * the timer is marked firing. The caller holds rcu_read_lock(), which
+ * protects the timer and the task which is expiring it from being freed.
+ */
+static void posix_cpu_timer_wait_running(struct k_itimer *timr)
+{
+ struct task_struct *tsk = rcu_dereference(timr->it.cpu.handling);
+
+ /* Has the handling task completed expiry already? */
+ if (!tsk)
+ return;
+
+ /* Ensure that the task cannot go away */
+ get_task_struct(tsk);
+ /* Now drop the RCU protection so the mutex can be locked */
+ rcu_read_unlock();
+ /* Wait on the expiry mutex */
+ mutex_lock(&tsk->posix_cputimers_work.mutex);
+ /* Release it immediately again. */
+ mutex_unlock(&tsk->posix_cputimers_work.mutex);
+ /* Drop the task reference. */
+ put_task_struct(tsk);
+ /* Relock RCU so the callsite is balanced */
+ rcu_read_lock();
+}
+
+static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
+{
+ /* Ensure that timr->it.cpu.handling task cannot go away */
+ rcu_read_lock();
+ spin_unlock_irq(&timr->it_lock);
+ posix_cpu_timer_wait_running(timr);
+ rcu_read_unlock();
+ /* @timr is on stack and is valid */
+ spin_lock_irq(&timr->it_lock);
}
/*
@@ -1177,6 +1221,7 @@ void clear_posix_cputimers_work(struct task_struct *p)
sizeof(p->posix_cputimers_work.work));
init_task_work(&p->posix_cputimers_work.work,
posix_cpu_timers_work);
+ mutex_init(&p->posix_cputimers_work.mutex);
p->posix_cputimers_work.scheduled = false;
}
@@ -1255,6 +1300,18 @@ static inline void __run_posix_cpu_timers(struct task_struct *tsk)
lockdep_posixtimer_exit();
}
+static void posix_cpu_timer_wait_running(struct k_itimer *timr)
+{
+ cpu_relax();
+}
+
+static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
+{
+ spin_unlock_irq(&timr->it_lock);
+ cpu_relax();
+ spin_lock_irq(&timr->it_lock);
+}
+
static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
{
return false;
@@ -1363,6 +1420,8 @@ static void handle_posix_cpu_timers(struct task_struct *tsk)
*/
if (likely(cpu_firing >= 0))
cpu_timer_fire(timer);
+ /* See posix_cpu_timer_wait_running() */
+ rcu_assign_pointer(timer->it.cpu.handling, NULL);
spin_unlock(&timer->it_lock);
}
}
@@ -1497,23 +1556,16 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
expires = cpu_timer_getexpires(&timer.it.cpu);
error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
if (!error) {
- /*
- * Timer is now unarmed, deletion can not fail.
- */
+ /* Timer is now unarmed, deletion can not fail. */
posix_cpu_timer_del(&timer);
+ } else {
+ while (error == TIMER_RETRY) {
+ posix_cpu_timer_wait_running_nsleep(&timer);
+ error = posix_cpu_timer_del(&timer);
+ }
}
- spin_unlock_irq(&timer.it_lock);
- while (error == TIMER_RETRY) {
- /*
- * We need to handle case when timer was or is in the
- * middle of firing. In other cases we already freed
- * resources.
- */
- spin_lock_irq(&timer.it_lock);
- error = posix_cpu_timer_del(&timer);
- spin_unlock_irq(&timer.it_lock);
- }
+ spin_unlock_irq(&timer.it_lock);
if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
/*
@@ -1623,6 +1675,7 @@ const struct k_clock clock_posix_cpu = {
.timer_del = posix_cpu_timer_del,
.timer_get = posix_cpu_timer_get,
.timer_rearm = posix_cpu_timer_rearm,
+ .timer_wait_running = posix_cpu_timer_wait_running,
};
const struct k_clock clock_process = {
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 0c8a87a11b39..808a247205a9 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -846,6 +846,10 @@ static struct k_itimer *timer_wait_running(struct k_itimer *timer,
rcu_read_lock();
unlock_timer(timer, *flags);
+ /*
+ * kc->timer_wait_running() might drop RCU lock. So @timer
+ * cannot be touched anymore after the function returns!
+ */
if (!WARN_ON_ONCE(!kc->timer_wait_running))
kc->timer_wait_running(timer);
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 46789356f856..65b8658da829 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -218,9 +218,19 @@ static void tick_setup_device(struct tick_device *td,
* this cpu:
*/
if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
+ ktime_t next_p;
+ u32 rem;
+
tick_do_timer_cpu = cpu;
- tick_next_period = ktime_get();
+ next_p = ktime_get();
+ div_u64_rem(next_p, TICK_NSEC, &rem);
+ if (rem) {
+ next_p -= rem;
+ next_p += TICK_NSEC;
+ }
+
+ tick_next_period = next_p;
#ifdef CONFIG_NO_HZ_FULL
/*
* The boot CPU may be nohz_full, in which case set
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a46506f7ec6d..52254679ec48 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -647,43 +647,67 @@ static void tick_nohz_update_jiffies(ktime_t now)
touch_softlockup_watchdog_sched();
}
-/*
- * Updates the per-CPU time idle statistics counters
- */
-static void
-update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
+static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
{
ktime_t delta;
- if (ts->idle_active) {
- delta = ktime_sub(now, ts->idle_entrytime);
- if (nr_iowait_cpu(cpu) > 0)
- ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
- else
- ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
- ts->idle_entrytime = now;
- }
+ if (WARN_ON_ONCE(!ts->idle_active))
+ return;
- if (last_update_time)
- *last_update_time = ktime_to_us(now);
+ delta = ktime_sub(now, ts->idle_entrytime);
-}
+ write_seqcount_begin(&ts->idle_sleeptime_seq);
+ if (nr_iowait_cpu(smp_processor_id()) > 0)
+ ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
+ else
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
-static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
-{
- update_ts_time_stats(smp_processor_id(), ts, now, NULL);
+ ts->idle_entrytime = now;
ts->idle_active = 0;
+ write_seqcount_end(&ts->idle_sleeptime_seq);
sched_clock_idle_wakeup_event();
}
static void tick_nohz_start_idle(struct tick_sched *ts)
{
+ write_seqcount_begin(&ts->idle_sleeptime_seq);
ts->idle_entrytime = ktime_get();
ts->idle_active = 1;
+ write_seqcount_end(&ts->idle_sleeptime_seq);
+
sched_clock_idle_sleep_event();
}
+static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
+ bool compute_delta, u64 *last_update_time)
+{
+ ktime_t now, idle;
+ unsigned int seq;
+
+ if (!tick_nohz_active)
+ return -1;
+
+ now = ktime_get();
+ if (last_update_time)
+ *last_update_time = ktime_to_us(now);
+
+ do {
+ seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
+
+ if (ts->idle_active && compute_delta) {
+ ktime_t delta = ktime_sub(now, ts->idle_entrytime);
+
+ idle = ktime_add(*sleeptime, delta);
+ } else {
+ idle = *sleeptime;
+ }
+ } while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq));
+
+ return ktime_to_us(idle);
+
+}
+
/**
* get_cpu_idle_time_us - get the total idle time of a CPU
* @cpu: CPU number to query
@@ -691,7 +715,10 @@ static void tick_nohz_start_idle(struct tick_sched *ts)
* counters if NULL.
*
* Return the cumulative idle time (since boot) for a given
- * CPU, in microseconds.
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
*
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.
@@ -701,27 +728,9 @@ static void tick_nohz_start_idle(struct tick_sched *ts)
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
- ktime_t now, idle;
-
- if (!tick_nohz_active)
- return -1;
-
- now = ktime_get();
- if (last_update_time) {
- update_ts_time_stats(cpu, ts, now, last_update_time);
- idle = ts->idle_sleeptime;
- } else {
- if (ts->idle_active && !nr_iowait_cpu(cpu)) {
- ktime_t delta = ktime_sub(now, ts->idle_entrytime);
-
- idle = ktime_add(ts->idle_sleeptime, delta);
- } else {
- idle = ts->idle_sleeptime;
- }
- }
-
- return ktime_to_us(idle);
+ return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime,
+ !nr_iowait_cpu(cpu), last_update_time);
}
EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
@@ -732,7 +741,10 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
* counters if NULL.
*
* Return the cumulative iowait time (since boot) for a given
- * CPU, in microseconds.
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
*
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.
@@ -742,26 +754,9 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
- ktime_t now, iowait;
- if (!tick_nohz_active)
- return -1;
-
- now = ktime_get();
- if (last_update_time) {
- update_ts_time_stats(cpu, ts, now, last_update_time);
- iowait = ts->iowait_sleeptime;
- } else {
- if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
- ktime_t delta = ktime_sub(now, ts->idle_entrytime);
-
- iowait = ktime_add(ts->iowait_sleeptime, delta);
- } else {
- iowait = ts->iowait_sleeptime;
- }
- }
-
- return ktime_to_us(iowait);
+ return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime,
+ nr_iowait_cpu(cpu), last_update_time);
}
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
@@ -1094,10 +1089,16 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
return true;
}
-static void __tick_nohz_idle_stop_tick(struct tick_sched *ts)
+/**
+ * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
+ *
+ * When the next event is more than a tick into the future, stop the idle tick
+ */
+void tick_nohz_idle_stop_tick(void)
{
- ktime_t expires;
+ struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
int cpu = smp_processor_id();
+ ktime_t expires;
/*
* If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
@@ -1129,16 +1130,6 @@ static void __tick_nohz_idle_stop_tick(struct tick_sched *ts)
}
}
-/**
- * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
- *
- * When the next event is more than a tick into the future, stop the idle tick
- */
-void tick_nohz_idle_stop_tick(void)
-{
- __tick_nohz_idle_stop_tick(this_cpu_ptr(&tick_cpu_sched));
-}
-
void tick_nohz_idle_retain_tick(void)
{
tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 504649513399..5ed5a9d41d5a 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -22,65 +22,82 @@ enum tick_nohz_mode {
/**
* struct tick_sched - sched tick emulation and no idle tick control/stats
- * @sched_timer: hrtimer to schedule the periodic tick in high
- * resolution mode
- * @check_clocks: Notification mechanism about clocksource changes
- * @nohz_mode: Mode - one state of tick_nohz_mode
+ *
* @inidle: Indicator that the CPU is in the tick idle mode
* @tick_stopped: Indicator that the idle tick has been stopped
* @idle_active: Indicator that the CPU is actively in the tick idle mode;
* it is reset during irq handling phases.
- * @do_timer_lst: CPU was the last one doing do_timer before going idle
+ * @do_timer_last: CPU was the last one doing do_timer before going idle
* @got_idle_tick: Tick timer function has run with @inidle set
+ * @stalled_jiffies: Number of stalled jiffies detected across ticks
+ * @last_tick_jiffies: Value of jiffies seen on last tick
+ * @sched_timer: hrtimer to schedule the periodic tick in high
+ * resolution mode
* @last_tick: Store the last tick expiry time when the tick
* timer is modified for nohz sleeps. This is necessary
* to resume the tick timer operation in the timeline
* when the CPU returns from nohz sleep.
* @next_tick: Next tick to be fired when in dynticks mode.
* @idle_jiffies: jiffies at the entry to idle for idle time accounting
+ * @idle_waketime: Time when the idle was interrupted
+ * @idle_entrytime: Time when the idle call was entered
+ * @nohz_mode: Mode - one state of tick_nohz_mode
+ * @last_jiffies: Base jiffies snapshot when next event was last computed
+ * @timer_expires_base: Base time clock monotonic for @timer_expires
+ * @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
+ * @next_timer: Expiry time of next expiring timer for debugging purpose only
+ * @idle_expires: Next tick in idle, for debugging purpose only
* @idle_calls: Total number of idle calls
* @idle_sleeps: Number of idle calls, where the sched tick was stopped
- * @idle_entrytime: Time when the idle call was entered
- * @idle_waketime: Time when the idle was interrupted
* @idle_exittime: Time when the idle state was left
* @idle_sleeptime: Sum of the time slept in idle with sched tick stopped
* @iowait_sleeptime: Sum of the time slept in idle with sched tick stopped, with IO outstanding
- * @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
- * @timer_expires_base: Base time clock monotonic for @timer_expires
- * @next_timer: Expiry time of next expiring timer for debugging purpose only
* @tick_dep_mask: Tick dependency mask - is set, if someone needs the tick
- * @last_tick_jiffies: Value of jiffies seen on last tick
- * @stalled_jiffies: Number of stalled jiffies detected across ticks
+ * @check_clocks: Notification mechanism about clocksource changes
*/
struct tick_sched {
- struct hrtimer sched_timer;
- unsigned long check_clocks;
- enum tick_nohz_mode nohz_mode;
-
+ /* Common flags */
unsigned int inidle : 1;
unsigned int tick_stopped : 1;
unsigned int idle_active : 1;
unsigned int do_timer_last : 1;
unsigned int got_idle_tick : 1;
+ /* Tick handling: jiffies stall check */
+ unsigned int stalled_jiffies;
+ unsigned long last_tick_jiffies;
+
+ /* Tick handling */
+ struct hrtimer sched_timer;
ktime_t last_tick;
ktime_t next_tick;
unsigned long idle_jiffies;
- unsigned long idle_calls;
- unsigned long idle_sleeps;
- ktime_t idle_entrytime;
ktime_t idle_waketime;
- ktime_t idle_exittime;
- ktime_t idle_sleeptime;
- ktime_t iowait_sleeptime;
+
+ /* Idle entry */
+ seqcount_t idle_sleeptime_seq;
+ ktime_t idle_entrytime;
+
+ /* Tick stop */
+ enum tick_nohz_mode nohz_mode;
unsigned long last_jiffies;
- u64 timer_expires;
u64 timer_expires_base;
+ u64 timer_expires;
u64 next_timer;
ktime_t idle_expires;
+ unsigned long idle_calls;
+ unsigned long idle_sleeps;
+
+ /* Idle exit */
+ ktime_t idle_exittime;
+ ktime_t idle_sleeptime;
+ ktime_t iowait_sleeptime;
+
+ /* Full dynticks handling */
atomic_t tick_dep_mask;
- unsigned long last_tick_jiffies;
- unsigned int stalled_jiffies;
+
+ /* Clocksource changes */
+ unsigned long check_clocks;
};
extern struct tick_sched *tick_get_tick_sched(int cpu);
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-13 07:58:41 +0000