From: "Paul E. McKenney" <paulmck@kernel•org>
To: Valentin Schneider <vschneid@redhat•com>
Cc: Chen Yu <yu.c.chen@intel•com>,
Peter Zijlstra <peterz@infradead•org>,
linux-kernel@vger•kernel.org, sfr@canb•auug.org.au,
linux-next@vger•kernel.org, kernel-team@meta•com
Subject: Re: [BUG almost bisected] Splat in dequeue_rt_stack() and build error
Date: Wed, 28 Aug 2024 11:39:19 -0700 [thread overview]
Message-ID: <8094db32-5c81-4537-8809-ddfe92a0ac6c@paulmck-laptop> (raw)
In-Reply-To: <xhsmh4j74o6l9.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
On Wed, Aug 28, 2024 at 08:17:06PM +0200, Valentin Schneider wrote:
> On 28/08/24 09:35, Paul E. McKenney wrote:
> > On Wed, Aug 28, 2024 at 04:32:41PM +0200, Valentin Schneider wrote:
> >> On 28/08/24 21:44, Chen Yu wrote:
> >> >
> >> > One question, although there is no DEQUEUE_DELAYED flag, it is possible
> >> > the delayed task could be dequeued from CFS tree. Because the dequeue in
> >> > set_schedule() does not have DEQUEUE_SLEEP. And in dequeue_entity():
> >> >
> >> > bool sleep = flags & DEQUEUE_SLEEP;
> >> >
> >> > if (flags & DEQUEUE_DELAYED) {
> >> >
> >> > } else {
> >> > bool delay = sleep;
> >> > if (sched_feat(DELAY_DEQUEUE) && delay && //false
> >> > !entity_eligible(cfs_rq, se) {
> >> > //do not dequeue
> >> > }
> >> > }
> >> >
> >> > //dequeue the task <---- we should reach here?
> >> >
> >>
> >> You're quite right, so really here the main missing bit would be the final
> >> __block_task() that a DEQUEUE_DELAYED dequeue_entities() would get us.
> >
> > 50*TREE03 passed, yay! Thank you both!!!
>
> Fantastic, I'll hammer this into a "proper" patch then. Thanks again for
> all the testing!
>
> > I started a 500*TREE03.
> >
> > Yes, the odds all 50 passing given the baseline 52% failure rate is
> > something like 10^-16, but software bugs are not necessarily constrained
> > by elementary statistics...
>
> :-)
The 500*TREE03 run had exactly one failure that was the dreaded
enqueue_dl_entity() failure, followed by RCU CPU stall warnings.
But a huge improvement over the prior state!
Plus, this failure is likely unrelated (see earlier discussions with
Peter). I just started a 5000*TREE03 run, just in case we can now
reproduce this thing.
Thanx, Paul
next prev parent reply other threads:[~2024-08-28 18:39 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-21 21:57 [BUG almost bisected] Splat in dequeue_rt_stack() and build error Paul E. McKenney
2024-08-22 23:01 ` Paul E. McKenney
2024-08-23 7:47 ` Peter Zijlstra
2024-08-23 12:46 ` Paul E. McKenney
2024-08-23 21:51 ` Paul E. McKenney
2024-08-24 6:54 ` Peter Zijlstra
2024-08-24 15:26 ` Paul E. McKenney
2024-08-25 2:10 ` Paul E. McKenney
2024-08-25 19:36 ` Paul E. McKenney
2024-08-26 11:44 ` Valentin Schneider
2024-08-26 16:31 ` Paul E. McKenney
2024-08-27 10:03 ` Valentin Schneider
2024-08-27 15:41 ` Valentin Schneider
2024-08-27 17:33 ` Paul E. McKenney
2024-08-27 18:35 ` Paul E. McKenney
2024-08-27 20:30 ` Valentin Schneider
2024-08-27 20:36 ` Paul E. McKenney
2024-08-28 12:35 ` Valentin Schneider
2024-08-28 13:03 ` Paul E. McKenney
2024-08-28 13:40 ` Paul E. McKenney
2024-08-28 13:44 ` Chen Yu
2024-08-28 14:32 ` Valentin Schneider
2024-08-28 16:35 ` Paul E. McKenney
2024-08-28 18:17 ` Valentin Schneider
2024-08-28 18:39 ` Paul E. McKenney [this message]
2024-08-29 10:28 ` Paul E. McKenney
2024-08-29 13:50 ` Valentin Schneider
2024-08-29 14:13 ` Paul E. McKenney
2024-09-08 16:32 ` Paul E. McKenney
2024-09-13 14:08 ` Paul E. McKenney
2024-09-13 16:55 ` Valentin Schneider
2024-09-13 18:00 ` Paul E. McKenney
2024-09-30 19:09 ` Paul E. McKenney
2024-09-30 20:44 ` Valentin Schneider
2024-10-01 10:10 ` Paul E. McKenney
2024-10-01 12:52 ` Valentin Schneider
2024-10-01 16:47 ` Paul E. McKenney
2024-10-02 9:01 ` Tomas Glozar
2024-10-02 12:07 ` Paul E. McKenney
2024-10-10 11:24 ` Tomas Glozar
2024-10-10 15:01 ` Paul E. McKenney
2024-10-10 23:28 ` Paul E. McKenney
2024-10-14 18:55 ` Paul E. McKenney
2024-10-21 19:25 ` Paul E. McKenney
2024-11-14 18:16 ` Paul E. McKenney
2024-12-15 18:31 ` Paul E. McKenney
2024-12-16 14:38 ` Tomas Glozar
2024-12-16 19:36 ` Paul E. McKenney
2024-12-17 16:42 ` Paul E. McKenney
2024-10-22 6:33 ` Tomas Glozar
2024-10-03 8:40 ` Peter Zijlstra
2024-10-03 8:47 ` Peter Zijlstra
2024-10-03 9:27 ` Peter Zijlstra
2024-10-03 12:28 ` Peter Zijlstra
2024-10-03 12:45 ` Paul E. McKenney
2024-10-03 14:22 ` Peter Zijlstra
2024-10-03 16:04 ` Paul E. McKenney
2024-10-03 18:50 ` Peter Zijlstra
2024-10-03 19:12 ` Paul E. McKenney
2024-10-04 13:22 ` Paul E. McKenney
2024-10-04 13:35 ` Peter Zijlstra
2024-10-06 20:44 ` Paul E. McKenney
2024-10-07 9:34 ` Peter Zijlstra
2024-10-08 11:11 ` Peter Zijlstra
2024-10-08 16:24 ` Paul E. McKenney
2024-10-08 22:34 ` Paul E. McKenney
2024-10-03 12:44 ` Paul E. McKenney
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