sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task() (0905f04e) · Commits · 戴 / test

If a newly created task is selected to go to a different CPU in fork balance when it wakes up the first time, its load averages should not be removed from the source CPU since they are never added to it before. The same is also applicable to a never used group entity. Fix it in remove_entity_load_avg(): when entity's last_update_time is 0, simply return. This should precisely identify the case in question, because in other migrations, the last_update_time is set to 0 after remove_entity_load_avg(). Reported-by:

Steve Muckle <steve.muckle@linaro.org> Signed-off-by:

Yuyang Du <yuyang.du@intel.com> [peterz: cfs_rq_last_update_time] Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Juri Lelli <Juri.Lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Patrick Bellasi <patrick.bellasi@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vincent Guittot <vincent.guittot@linaro.org> Link: http://lkml.kernel.org/r/20151216233427.GJ28098@intel.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

+28 −10

Original line number	Diff line number	Diff line
		@@ -2900,27 +2900,45 @@ dequeue_entity_load_avg(struct cfs_rq cfs_rq, struct sched_entity se)
		max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
		}

		/*
		* Task first catches up with cfs_rq, and then subtract
		* itself from the cfs_rq (task must be off the queue now).
		*/
		void remove_entity_load_avg(struct sched_entity *se)
		{
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 last_update_time;

		#ifndef CONFIG_64BIT
		static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
		{
		u64 last_update_time_copy;
		u64 last_update_time;

		do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
		} while (last_update_time != last_update_time_copy);

		return last_update_time;
		}
		#else
		last_update_time = cfs_rq->avg.last_update_time;
		static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
		{
		return cfs_rq->avg.last_update_time;
		}
		#endif

		/*
		* Task first catches up with cfs_rq, and then subtract
		* itself from the cfs_rq (task must be off the queue now).
		*/
		void remove_entity_load_avg(struct sched_entity *se)
		{
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 last_update_time;

		/*
		* Newly created task or never used group entity should not be removed
		* from its (source) cfs_rq
		*/
		if (se->avg.last_update_time == 0)
		return;

		last_update_time = cfs_rq_last_update_time(cfs_rq);

		__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
		atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
		atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);

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