sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume) (8cb68b34) · Commits · 戴 / test

The hotplug code still triggers the warning about using a stale rq->clock value. Fix things up to actually run update_rq_clock() in a place where we record the 'UPDATED' flag, and then modify the annotation to retain this flag over the rq->lock fiddling that happens as a result of actually migrating all the tasks elsewhere. Reported-by:

Linus Torvalds <torvalds@linux-foundation.org> Tested-by:

Mike Galbraith <efault@gmx.de> Tested-by:

Sachin Sant <sachinp@linux.vnet.ibm.com> Tested-by:

Borislav Petkov <bp@suse.de> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by:

Matt Fleming <matt@codeblueprint.co.uk> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ross Zwisler <zwisler@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: ("sched/fair: Restore previous rq_flags when migrating tasks in hotplug") Link: http://lkml.kernel.org/r/20170202155506.GX6515@twins.programming.kicks-ass.net Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

+4 −10

Original line number	Diff line number	Diff line
		@@ -5557,7 +5557,7 @@ static void migrate_tasks(struct rq *dead_rq)
		{
		struct rq *rq = dead_rq;
		struct task_struct next, stop = rq->stop;
		struct rq_flags rf, old_rf;
		struct rq_flags rf;
		int dest_cpu;

		/*
		@@ -5576,7 +5576,9 @@ static void migrate_tasks(struct rq *dead_rq)
		* class method both need to have an up-to-date
		* value of rq->clock[_task]
		*/
		rq_pin_lock(rq, &rf);
		update_rq_clock(rq);
		rq_unpin_lock(rq, &rf);

		for (;;) {
		/*
		@@ -5589,7 +5591,7 @@ static void migrate_tasks(struct rq *dead_rq)
		/*
		* pick_next_task() assumes pinned rq->lock:
		*/
		rq_pin_lock(rq, &rf);
		rq_repin_lock(rq, &rf);
		next = pick_next_task(rq, &fake_task, &rf);
		BUG_ON(!next);
		next->sched_class->put_prev_task(rq, next);
		@@ -5618,13 +5620,6 @@ static void migrate_tasks(struct rq *dead_rq)
		continue;
		}

		/*
		* __migrate_task() may return with a different
		* rq->lock held and a new cookie in 'rf', but we need
		* to preserve rf::clock_update_flags for 'dead_rq'.
		*/
		old_rf = rf;

		/* Find suitable destination for @next, with force if needed. */
		dest_cpu = select_fallback_rq(dead_rq->cpu, next);

		@@ -5633,7 +5628,6 @@ static void migrate_tasks(struct rq *dead_rq)
		raw_spin_unlock(&rq->lock);
		rq = dead_rq;
		raw_spin_lock(&rq->lock);
		rf = old_rf;
		}
		raw_spin_unlock(&next->pi_lock);
		}

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