Re: [PATCH 1/3] sched/deadline: Fix warning in migrate_enable for boosted tasks
From: Wander Lairson Costa
Date: Tue Jul 23 2024 - 08:28:31 EST
On Tue, Jul 23, 2024 at 5:50 AM Juri Lelli <juri.lelli@xxxxxxxxxx> 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@xxxxxxxxxx>
> > 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
>