linux-kernel - Re: [PATCH 1/3] sched/deadline: Fix warning in migrate

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Message-ID: <CAAq0SU=c7vCq0honu=GpvLY=sL3xQHZ2N_=TmB23P=d4OXBcBQ@mail.gmail.com>
Date: Tue, 23 Jul 2024 09:28:07 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, "open list:SCHEDULER" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] sched/deadline: Fix warning in migrate_enable for
 boosted tasks

On Tue, Jul 23, 2024 at 5:50 AM Juri Lelli <juri.lelli@...hat.com> wrote:
>
> Hi Wander,
>
> On 22/07/24 10:29, Wander Lairson Costa wrote:
> > When running the following command:
> >
> > while true; do
> >     stress-ng --cyclic 30 --timeout 30s --minimize --quiet
> > done
> >
> > a warning is eventually triggered:
> >
> > WARNING: CPU: 43 PID: 2848 at kernel/sched/deadline.c:794
> > setup_new_dl_entity+0x13e/0x180
> > ...
> > Call Trace:
> >  <TASK>
> >  ? show_trace_log_lvl+0x1c4/0x2df
> >  ? enqueue_dl_entity+0x631/0x6e0
> >  ? setup_new_dl_entity+0x13e/0x180
> >  ? __warn+0x7e/0xd0
> >  ? report_bug+0x11a/0x1a0
> >  ? handle_bug+0x3c/0x70
> >  ? exc_invalid_op+0x14/0x70
> >  ? asm_exc_invalid_op+0x16/0x20
> >  enqueue_dl_entity+0x631/0x6e0
> >  enqueue_task_dl+0x7d/0x120
> >  __do_set_cpus_allowed+0xe3/0x280
> >  __set_cpus_allowed_ptr_locked+0x140/0x1d0
> >  __set_cpus_allowed_ptr+0x54/0xa0
> >  migrate_enable+0x7e/0x150
> >  rt_spin_unlock+0x1c/0x90
> >  group_send_sig_info+0xf7/0x1a0
> >  ? kill_pid_info+0x1f/0x1d0
> >  kill_pid_info+0x78/0x1d0
> >  kill_proc_info+0x5b/0x110
> >  __x64_sys_kill+0x93/0xc0
> >  do_syscall_64+0x5c/0xf0
> >  entry_SYSCALL_64_after_hwframe+0x6e/0x76
> >  RIP: 0033:0x7f0dab31f92b
> >
> > This warning occurs because set_cpus_allowed dequeues and enqueues tasks
> > with the ENQUEUE_RESTORE flag set. If the task is boosted, the warning
> > is triggered. A boosted task already had its parameters set by
> > rt_mutex_setprio, and a new call to setup_new_dl_entity is unnecessary,
> > hence the WARN_ON call.
> >
> > Check if we are requeueing a boosted task and avoid calling
> > setup_new_dl_entity if that's the case.
> >
> > Signed-off-by: Wander Lairson Costa <wander@...hat.com>
> > Fixes: 2279f540ea7d ("sched/deadline: Fix priority inheritance with multiple scheduling classes")
>
> I believe your fix makes sense to me. I only wonder if however it
> actually fixes 295d6d5e37360 ("sched/deadline: Fix switching to
> -deadline") instead of the change you reference above?
>

That makes more sense, thanks.

> Thanks,
> Juri
>