Commit 4d25b35e authored by Matt Fleming's avatar Matt Fleming Committed by Ingo Molnar

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: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 1b1d6225
...@@ -5608,7 +5608,7 @@ static void migrate_tasks(struct rq *dead_rq) ...@@ -5608,7 +5608,7 @@ static void migrate_tasks(struct rq *dead_rq)
{ {
struct rq *rq = dead_rq; struct rq *rq = dead_rq;
struct task_struct *next, *stop = rq->stop; struct task_struct *next, *stop = rq->stop;
struct rq_flags rf; struct rq_flags rf, old_rf;
int dest_cpu; int dest_cpu;
/* /*
...@@ -5669,6 +5669,13 @@ static void migrate_tasks(struct rq *dead_rq) ...@@ -5669,6 +5669,13 @@ static void migrate_tasks(struct rq *dead_rq)
continue; 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. */ /* Find suitable destination for @next, with force if needed. */
dest_cpu = select_fallback_rq(dead_rq->cpu, next); dest_cpu = select_fallback_rq(dead_rq->cpu, next);
...@@ -5677,6 +5684,7 @@ static void migrate_tasks(struct rq *dead_rq) ...@@ -5677,6 +5684,7 @@ static void migrate_tasks(struct rq *dead_rq)
raw_spin_unlock(&rq->lock); raw_spin_unlock(&rq->lock);
rq = dead_rq; rq = dead_rq;
raw_spin_lock(&rq->lock); raw_spin_lock(&rq->lock);
rf = old_rf;
} }
raw_spin_unlock(&next->pi_lock); raw_spin_unlock(&next->pi_lock);
} }
......
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