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From: Kirill Tkhai <tkhai@yandex.ru>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>,
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Subject: Re: [PATCH] sched/dl: Fix race between dl_task_timer() and sched_setaffinity()
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20.05.2014, 09:08, "Kirill Tkhai" <tkhai@yandex.ru>:
> 20.05.2014, 04:00, "Peter Zijlstra" <peterz@infradead.org>:
>
>> šOn Mon, May 19, 2014 at 11:31:19PM +0400, Kirill Tkhai wrote:
>>> šš@@ -513,9 +513,17 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
>>> ššššššššššššššššššššššššššššššššššššššššššššššššššššššššstruct sched_dl_entity,
>>> ššššššššššššššššššššššššššššššššššššššššššššššššššššššššdl_timer);
>>> šššššššššššstruct task_struct *p = dl_task_of(dl_se);
>>> šš- struct rq *rq = task_rq(p);
>>> šš+ struct rq *rq;
>>> šš+again:
>>> šš+ rq = task_rq(p);
>>> šššššššššššraw_spin_lock(&rq->lock);
>>>
>>> šš+ if (unlikely(rq != task_rq(p))) {
>>> šš+ /* Task was moved, retrying. */
>>> šš+ raw_spin_unlock(&rq->lock);
>>> šš+ goto again;
>>> šš+ }
>>> šš+
>> šThat thing is called: rq = __task_rq_lock(p);
>
> But p->pi_lock is not held. The problem is __task_rq_lock() has lockdep assert.
> Should we change it?

Or make something like this?

static inline struct rq *_task_rq_lock(struct task_struct *p)
{
        lockdep_assert_held(&p->pi_lock);

        return __task_rq_lock(p);
}

Thanks!