Commit-ID: 4d25b35ea3729affd37d69c78191ce6f92766e1a
Gitweb: http://git.kernel.org/tip/4d25b35ea3729affd37d69c78191ce6f92766e1a
Author: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 26 Oct 2016 16:15:44 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 30 Jan 2017 11:46:35 +0100
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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f983e8..3b248b0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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);
}
--
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