On Sat, 17 May 2014 01:30:03 +0400
Kirill Tkhai <tkhai@xxxxxxxxx> wrote:
> The race is in unlocked task_rq() access. In pair with parallel
> call of sched_setaffinity() it may be a reason of corruption
> of internal rq's data.
>
Sure, the thing can happen!
> Signed-off-by: Kirill Tkhai <tkhai@xxxxxxxxx>
> CC: Juri Lelli <juri.lelli@xxxxxxxxx>
> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v3.14
> ---
> kernel/sched/deadline.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 800e99b..ffb023a 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -513,9 +513,16 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
> struct sched_dl_entity,
> dl_timer);
> struct task_struct *p = dl_task_of(dl_se);
> - struct rq *rq = task_rq(p);
> + struct rq *rq;
We could maybe add a comment here, in line with what we have below, to
document why we need this.
Thanks,
- Juri
> +again:
> + rq = task_rq(p);
> raw_spin_lock(&rq->lock);
>
> + if (unlikely(rq != task_rq(p))) {
> + raw_spin_unlock(&rq->lock);
> + goto again;
> + }
> +
> /*
> * We need to take care of a possible races here. In fact, the
> * task might have changed its scheduling policy to something
>
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