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sched/fair: Restore previous rq_flags when migrating tasks in hotplug 

__migrate_task() can return with a different runqueue locked than the
one we passed as an argument. So that we can repin the lock in
migrate_tasks() (and keep the update_rq_clock() bit) we need to
restore the old rq_flags before repinning.

Note that it wouldn't be correct to change move_queued_task() to repin
because of the change of runqueue and the fact that having an
up-to-date clock on the initial rq doesn't mean the new rq has one
too.

Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Matt Fleming 2016-10-26 16:15:44 +01:00 committed by Ingo Molnar
parent 1b1d62254d
commit 4d25b35ea3
1 changed files with 9 additions and 1 deletions
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10
kernel/sched/core.c
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@ -5608,7 +5608,7 @@ static void migrate_tasks(struct rq *dead_rq)
{
struct rq *rq = dead_rq;
struct task_struct *next, *stop = rq->stop;
struct rq_flags rf;
struct rq_flags rf, old_rf;
int dest_cpu;
/*
@ -5669,6 +5669,13 @@ 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);
@ -5677,6 +5684,7 @@ 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);
}