linux-kernel - Re: [BUG almost bisected] Splat in dequeue_rt

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Message-ID: <xhsmho75fo6e4.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Mon, 26 Aug 2024 13:44:35 +0200
From: Valentin Schneider <vschneid@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>, "Paul E. McKenney"
 <paulmck@...nel.org>
Cc: linux-kernel@...r.kernel.org, sfr@...b.auug.org.au,
 linux-next@...r.kernel.org, kernel-team@...a.com
Subject: Re: [BUG almost bisected] Splat in dequeue_rt_stack() and build error

On 23/08/24 09:47, Peter Zijlstra wrote:
> On Wed, Aug 21, 2024 at 02:57:16PM -0700, Paul E. McKenney wrote:
>
>> 2e0199df252a ("sched/fair: Prepare exit/cleanup paths for delayed_dequeue")
>>
>> The preceding commit is very reliable.
>>
>> Only instead of (or maybe as well as?) introducing the dequeue_rt_stack()
>> bug, the 2e0199df252a commit introduced a build bug:
>>
>> ------------------------------------------------------------------------
>>
>> In file included from kernel/sched/fair.c:54:
>> kernel/sched/fair.c: In function ‘switched_from_fair’:
>> kernel/sched/sched.h:2154:58: error: ‘__SCHED_FEAT_DELAY_ZERO’ undeclared (first use in this function); did you mean ‘__SCHED_FEAT_LATENCY_WARN’?
>>  2154 | #define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
>>       |                                                          ^~~~~~~~~~~~~
>> kernel/sched/fair.c:12878:21: note: in expansion of macro ‘sched_feat’
>> 12878 |                 if (sched_feat(DELAY_ZERO) && p->se.vlag > 0)
>>       |                     ^~~~~~~~~~
>> kernel/sched/sched.h:2154:58: note: each undeclared identifier is reported only once for each function it appears in
>>  2154 | #define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
>>       |                                                          ^~~~~~~~~~~~~
>> kernel/sched/fair.c:12878:21: note: in expansion of macro ‘sched_feat’
>> 12878 |                 if (sched_feat(DELAY_ZERO) && p->se.vlag > 0)
>>       |                     ^~~~~~~~~~
>>
>
> Oh gawd, last minute back-merges :/
>
> Does the below help any? That's more or less what it was before Valentin
> asked me why it was weird like that :-)
>

Woops...