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Message-ID: <aMHKuRBUSeNFiLVF@gpd4>
Date: Wed, 10 Sep 2025 21:00:09 +0200
From: Andrea Righi <arighi@...dia.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: tj@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
juri.lelli@...hat.com, vincent.guittot@...aro.org,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
mgorman@...e.de, vschneid@...hat.com, longman@...hat.com,
hannes@...xchg.org, mkoutny@...e.com, void@...ifault.com,
changwoo@...lia.com, cgroups@...r.kernel.org,
sched-ext@...ts.linux.dev, liuwenfang@...or.com, tglx@...utronix.de
Subject: Re: [PATCH 00/14] sched: Support shared runqueue locking
On Wed, Sep 10, 2025 at 08:35:55PM +0200, Peter Zijlstra wrote:
> On Wed, Sep 10, 2025 at 07:32:12PM +0200, Andrea Righi wrote:
>
> > [ 15.160400] Call Trace:
> > [ 15.160706] dequeue_task_scx+0x14a/0x270
> > [ 15.160857] move_queued_task+0x7d/0x2d0
> > [ 15.160952] affine_move_task+0x6ca/0x700
> > [ 15.161210] __set_cpus_allowed_ptr+0x64/0xa0
> > [ 15.161348] __sched_setaffinity+0x72/0x100
> > [ 15.161459] sched_setaffinity+0x261/0x2f0
> > [ 15.161569] __x64_sys_sched_setaffinity+0x50/0x80
> > [ 15.161705] do_syscall_64+0xbb/0x370
> > [ 15.161816] entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > Are we missing a DEQUEUE_LOCKED in the sched_setaffinity() path?
>
> Yeah, the affine_move_task->move_queued_task path is messed up. It
> relied on raw_spin_lock_irqsave(&p->pi_lock); rq_lock(rq); being
> equivalent to task_rq_lock(), which is no longer true.
>
> I fixed a few such sites earlier today but missed this one.
>
> I'll go untangle it, but probably something for tomorrow, I'm bound to
> make a mess of it now :-)
Sure! I’ll run more tests in the meantime. For now, that's the only issue
I've found. :)
Thanks!
-Andrea
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