Linux-libre 4.8.2-gnupck-4.8.2-gnu

1 files changed, 38 insertions, 57 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 536ada80f..2ec7c0022 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.
 	 */
@@ -933,11 +945,11 @@ 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 +1104,6 @@ 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 +1114,8 @@ 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 +1192,7 @@ 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. */