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FAILED: patch "[PATCH] timers: Forward the wheel clock whenever possible" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jul 20, 2020

Subsystems (3)
Stable branch High-resolution timers, timer wheel, clockevents Nohz, dynticks support
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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a683f390b93f4d1292f849fc48d28e322046120f Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Mon, 4 Jul 2016 09:50:36 +0000
Subject: [PATCH] timers: Forward the wheel clock whenever possible

The wheel clock is stale when a CPU goes into a long idle sleep. This has the side effect that timers which are queued end up in the outer wheel levels. That results in coarser granularity.

To solve this, we keep track of the idle state and forward the wheel clock whenever possible.

Signed-off-by Thomas Gleixner <[email protected]>
Cc Arjan van de Ven <[email protected]>
Cc Chris Mason <[email protected]>
Cc Eric Dumazet <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc George Spelvin <[email protected]>
Cc Josh Triplett <[email protected]>
Cc Len Brown <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Paul E. McKenney <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Rik van Riel <[email protected]>
Cc [email protected]
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
kernel/time/tick-internal.h +1 -0
index 966a5a6fdd0a..f738251000fe 100644
@@ -164,3 +164,4 @@ static inline void timers_update_migration(bool update_nohz) { }
 DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
 
 extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem);
+void timer_clear_idle(void);
kernel/time/tick-sched.c +12 -0
index 69abc7bfe80f..5d81f9aa30d2 100644
@@ -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.

@@ -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();
 	/*
kernel/time/timer.c +107 -21

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