diff options
| author | Daniel Lezcano <daniel.lezcano@linaro.org> | 2014-01-17 10:04:02 +0100 |
|---|---|---|
| committer | Daniel Lezcano <daniel.lezcano@linaro.org> | 2014-02-06 10:16:23 +0000 |
| commit | 9106dbfdfca0fa0cee7f945a723dded89a2f8e4a (patch) | |
| tree | 1fd8cdac2f3210c315cc818b1360a265ca25ae4d | |
| parent | b60523258b78451864adfbfea5bb857fba41b791 (diff) | |
sched: Fix race in idle_balance()
The scheduler main function 'schedule()' checks if there are no more tasks
on the runqueue. Then it checks if a task should be pulled in the current
runqueue in idle_balance() assuming it will go to idle otherwise.
But the idle_balance() releases the rq->lock in order to lookup in the sched
domains and takes the lock again right after. That opens a window where
another cpu may put a task in our runqueue, so we won't go to idle but
we have filled the idle_stamp, thinking we will.
This patch closes the window by checking if the runqueue has been modified
but without pulling a task after taking the lock again, so we won't go to idle
right after in the __schedule() function.
Cc: linaro-kernel@lists.linaro.org
Cc: alex.shi@linaro.org
Cc: peterz@infradead.org
Cc: mingo@kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389949444-14821-2-git-send-email-daniel.lezcano@linaro.org
| -rw-r--r-- | kernel/sched/fair.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 428bc9d2c383..5ebc6817c036 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6589,6 +6589,13 @@ void idle_balance(struct rq *this_rq) raw_spin_lock(&this_rq->lock); + /* + * While browsing the domains, we released the rq lock. + * A task could have be enqueued in the meantime + */ + if (this_rq->nr_running && !pulled_task) + return; + if (pulled_task || time_after(jiffies, this_rq->next_balance)) { /* * We are going idle. next_balance may be set based on |