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-rw-r--r--kernel/time/tick-sched.c98
1 files changed, 39 insertions, 59 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 536ada80f6dd..204fdc86863d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -31,7 +31,7 @@
#include <trace/events/timer.h>
/*
- * Per cpu nohz control structure
+ * Per-CPU nohz control structure
*/
static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
@@ -61,7 +61,7 @@ static void tick_do_update_jiffies64(ktime_t now)
if (delta.tv64 < tick_period.tv64)
return;
- /* Reevalute with jiffies_lock held */
+ /* Reevaluate with jiffies_lock held */
write_seqlock(&jiffies_lock);
delta = ktime_sub(now, last_jiffies_update);
@@ -116,8 +116,8 @@ static void tick_sched_do_timer(ktime_t now)
#ifdef CONFIG_NO_HZ_COMMON
/*
* Check if the do_timer duty was dropped. We don't care about
- * concurrency: This happens only when the cpu in charge went
- * into a long sleep. If two cpus happen to assign themself to
+ * concurrency: This happens only when the CPU in charge went
+ * into a long sleep. If two CPUs happen to assign themselves to
* this duty, then the jiffies update is still serialized by
* jiffies_lock.
*/
@@ -349,7 +349,7 @@ void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bi
/*
* Re-evaluate the need for the tick as we switch the current task.
* It might need the tick due to per task/process properties:
- * perf events, posix cpu timers, ...
+ * perf events, posix CPU timers, ...
*/
void __tick_nohz_task_switch(void)
{
@@ -509,8 +509,8 @@ int tick_nohz_tick_stopped(void)
*
* In case the sched_tick was stopped on this CPU, we have to check if jiffies
* must be updated. Otherwise an interrupt handler could use a stale jiffy
- * value. We do this unconditionally on any cpu, as we don't know whether the
- * cpu, which has the update task assigned is in a long sleep.
+ * value. We do this unconditionally on any CPU, as we don't know whether the
+ * CPU, which has the update task assigned is in a long sleep.
*/
static void tick_nohz_update_jiffies(ktime_t now)
{
@@ -526,7 +526,7 @@ static void tick_nohz_update_jiffies(ktime_t now)
}
/*
- * Updates the per cpu time idle statistics counters
+ * 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)
@@ -566,12 +566,12 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
}
/**
- * get_cpu_idle_time_us - get the total idle time of a cpu
+ * get_cpu_idle_time_us - get the total idle time of a CPU
* @cpu: CPU number to query
* @last_update_time: variable to store update time in. Do not update
* counters if NULL.
*
- * Return the cummulative idle time (since boot) for a given
+ * Return the cumulative idle time (since boot) for a given
* CPU, in microseconds.
*
* This time is measured via accounting rather than sampling,
@@ -607,12 +607,12 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
/**
- * get_cpu_iowait_time_us - get the total iowait time of a cpu
+ * get_cpu_iowait_time_us - get the total iowait time of a CPU
* @cpu: CPU number to query
* @last_update_time: variable to store update time in. Do not update
* counters if NULL.
*
- * Return the cummulative iowait time (since boot) for a given
+ * Return the cumulative iowait time (since boot) for a given
* CPU, in microseconds.
*
* This time is measured via accounting rather than sampling,
@@ -700,6 +700,12 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
delta = next_tick - basemono;
if (delta <= (u64)TICK_NSEC) {
tick.tv64 = 0;
+
+ /*
+ * Tell the timer code that the base is not idle, i.e. undo
+ * the effect of get_next_timer_interrupt():
+ */
+ timer_clear_idle();
/*
* We've not stopped the tick yet, and there's a timer in the
* next period, so no point in stopping it either, bail.
@@ -726,14 +732,14 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
}
/*
- * If this cpu is the one which updates jiffies, then give up
- * the assignment and let it be taken by the cpu which runs
- * the tick timer next, which might be this cpu as well. If we
+ * If this CPU is the one which updates jiffies, then give up
+ * the assignment and let it be taken by the CPU which runs
+ * the tick timer next, which might be this CPU as well. If we
* don't drop this here the jiffies might be stale and
* do_timer() never invoked. Keep track of the fact that it
- * was the one which had the do_timer() duty last. If this cpu
+ * was the one which had the do_timer() duty last. If this CPU
* is the one which had the do_timer() duty last, we limit the
- * sleep time to the timekeeping max_deferement value.
+ * sleep time to the timekeeping max_deferment value.
* Otherwise we can sleep as long as we want.
*/
delta = timekeeping_max_deferment();
@@ -809,6 +815,12 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
tick_do_update_jiffies64(now);
cpu_load_update_nohz_stop();
+ /*
+ * Clear the timer idle flag, so we avoid IPIs on remote queueing and
+ * the clock forward checks in the enqueue path:
+ */
+ timer_clear_idle();
+
calc_load_exit_idle();
touch_softlockup_watchdog_sched();
/*
@@ -841,9 +853,9 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
{
/*
- * If this cpu is offline and it is the one which updates
+ * If this CPU is offline and it is the one which updates
* jiffies, then give up the assignment and let it be taken by
- * the cpu which runs the tick timer next. If we don't drop
+ * the CPU which runs the tick timer next. If we don't drop
* this here the jiffies might be stale and do_timer() never
* invoked.
*/
@@ -896,11 +908,10 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts)
ktime_t now, expires;
int cpu = smp_processor_id();
- now = tick_nohz_start_idle(ts);
-
if (can_stop_idle_tick(cpu, ts)) {
int was_stopped = ts->tick_stopped;
+ now = tick_nohz_start_idle(ts);
ts->idle_calls++;
expires = tick_nohz_stop_sched_tick(ts, now, cpu);
@@ -933,11 +944,11 @@ void tick_nohz_idle_enter(void)
WARN_ON_ONCE(irqs_disabled());
/*
- * Update the idle state in the scheduler domain hierarchy
- * when tick_nohz_stop_sched_tick() is called from the idle loop.
- * State will be updated to busy during the first busy tick after
- * exiting idle.
- */
+ * Update the idle state in the scheduler domain hierarchy
+ * when tick_nohz_stop_sched_tick() is called from the idle loop.
+ * State will be updated to busy during the first busy tick after
+ * exiting idle.
+ */
set_cpu_sd_state_idle();
local_irq_disable();
@@ -1092,35 +1103,6 @@ static void tick_nohz_switch_to_nohz(void)
tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
}
-/*
- * When NOHZ is enabled and the tick is stopped, we need to kick the
- * tick timer from irq_enter() so that the jiffies update is kept
- * alive during long running softirqs. That's ugly as hell, but
- * correctness is key even if we need to fix the offending softirq in
- * the first place.
- *
- * Note, this is different to tick_nohz_restart. We just kick the
- * timer and do not touch the other magic bits which need to be done
- * when idle is left.
- */
-static void tick_nohz_kick_tick(struct tick_sched *ts, ktime_t now)
-{
-#if 0
- /* Switch back to 2.6.27 behaviour */
- ktime_t delta;
-
- /*
- * Do not touch the tick device, when the next expiry is either
- * already reached or less/equal than the tick period.
- */
- delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
- if (delta.tv64 <= tick_period.tv64)
- return;
-
- tick_nohz_restart(ts, now);
-#endif
-}
-
static inline void tick_nohz_irq_enter(void)
{
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
@@ -1131,10 +1113,8 @@ static inline void tick_nohz_irq_enter(void)
now = ktime_get();
if (ts->idle_active)
tick_nohz_stop_idle(ts, now);
- if (ts->tick_stopped) {
+ if (ts->tick_stopped)
tick_nohz_update_jiffies(now);
- tick_nohz_kick_tick(ts, now);
- }
}
#else
@@ -1211,7 +1191,7 @@ void tick_setup_sched_timer(void)
hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
ts->sched_timer.function = tick_sched_timer;
- /* Get the next period (per cpu) */
+ /* Get the next period (per-CPU) */
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
/* Offset the tick to avert jiffies_lock contention. */