From: Quentin Perret <qperret@google.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: kernel test robot <lkp@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Aaron Lu <aaron.lwe@gmail.com>, Phil Auld <pauld@redhat.com>,
Julien Desfossez <jdesfossez@digitalocean.com>,
Nishanth Aravamudan <naravamudan@digitalocean.com>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
lkp@01.org
Subject: Re: [sched] 10e7071b2f: BUG:kernel_NULL_pointer_dereference,address
Date: Thu, 7 Nov 2019 12:43:55 +0000 [thread overview]
Message-ID: <20191107124355.GA161316@google.com> (raw)
In-Reply-To: <6a23a062-9b82-668d-7945-8da34f4dc5f0@arm.com>
On Thursday 07 Nov 2019 at 12:37:09 (+0000), Valentin Schneider wrote:
> On 07/11/2019 12:15, Quentin Perret wrote:
> > On Thursday 07 Nov 2019 at 12:09:22 (+0000), Quentin Perret wrote:
> >> sched_move_task() follows what Peter called the 'change' pattern, so I'm
> >> thinking this is most likely the same issue. Dropping the lock causes an
> >> unmitigated race between sched_move_task() and pick_next_task_dl(), so
> >> hilarity ensues (set_next_task() being called twice for instance).
> >
> > Bah, scratch that. 10e7071b2 is clearly before the pick_next_task()
> > rework, so that's not it :(
> >
>
> And besides we don't drop the lock until reaching pick_next_task_fair(),
> and the splat says it died on pick_next_task_dl() which happens earlier.
Right, with the rework of pick_next_task(), we would in fact drop the
lock before calling pick_next_task_dl(), which would explain the issue,
hence my confusion.
But that doesn't apply here, so this is another problem :(
Sorry for the noise,
Quentin
next prev parent reply other threads:[~2019-11-07 12:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 9:08 [sched] 10e7071b2f: BUG:kernel_NULL_pointer_dereference,address kernel test robot
2019-11-07 11:41 ` Valentin Schneider
2019-11-07 12:09 ` Quentin Perret
2019-11-07 12:15 ` Quentin Perret
2019-11-07 12:37 ` Valentin Schneider
2019-11-07 12:43 ` Quentin Perret [this message]
2019-11-07 13:51 ` Valentin Schneider
2019-11-07 14:46 ` Peter Zijlstra
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