Commit 57ccdf44 authored Sep 07, 2016 by Wanpeng Li Committed by Thomas Gleixner Sep 13, 2016

tick/nohz: Prevent stopping the tick on an offline CPU



can_stop_full_tick() has no check for offline cpus. So it allows to stop
the tick on an offline cpu from the interrupt return path, which is wrong
and subsequently makes irq_work_needs_cpu() warn about being called for an
offline cpu.

Commit f7ea0fd6 ("tick: Don't invoke tick_nohz_stop_sched_tick() if
the cpu is offline") added prevention for can_stop_idle_tick(), but forgot
to do the same in can_stop_full_tick(). Add it.

[ tglx: Massaged changelog ]

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1473245473-4463-1-git-send-email-wanpeng.li@hotmail.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 2ea3401e

kernel/time/tick-sched.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -186,10 +186,13 @@ static bool check_tick_dependency(atomic_t *dep)
		return false;
		}

		static bool can_stop_full_tick(struct tick_sched *ts)
		static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
		{
		WARN_ON_ONCE(!irqs_disabled());

		if (unlikely(!cpu_online(cpu)))
		return false;

		if (check_tick_dependency(&tick_dep_mask))
		return false;

		@@ -843,7 +846,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
		if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
		return;

		if (can_stop_full_tick(ts))
		if (can_stop_full_tick(cpu, ts))
		tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
		else if (ts->tick_stopped)
		tick_nohz_restart_sched_tick(ts, ktime_get());

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