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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>
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1b1d62254d
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1 changed files with 9 additions and 1 deletions
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@ -5608,7 +5608,7 @@ static void migrate_tasks(struct rq *dead_rq)
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{
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struct rq *rq = dead_rq;
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struct task_struct *next, *stop = rq->stop;
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struct rq_flags rf;
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struct rq_flags rf, old_rf;
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int dest_cpu;
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/*
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@ -5669,6 +5669,13 @@ static void migrate_tasks(struct rq *dead_rq)
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continue;
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}
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/*
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* __migrate_task() may return with a different
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* rq->lock held and a new cookie in 'rf', but we need
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* to preserve rf::clock_update_flags for 'dead_rq'.
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*/
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old_rf = rf;
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/* Find suitable destination for @next, with force if needed. */
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dest_cpu = select_fallback_rq(dead_rq->cpu, next);
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@ -5677,6 +5684,7 @@ static void migrate_tasks(struct rq *dead_rq)
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raw_spin_unlock(&rq->lock);
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rq = dead_rq;
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raw_spin_lock(&rq->lock);
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rf = old_rf;
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}
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raw_spin_unlock(&next->pi_lock);
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}
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