From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Scott Wood <swood@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Clark Williams <williams@redhat.com>,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Subject: Re: [PATCH RT 6/8] sched: migrate_enable: Set state to TASK_RUNNING
Date: Tue, 17 Sep 2019 17:31:10 +0200 [thread overview]
Message-ID: <20190917153110.fgi6ilb6mpfkcwbr@linutronix.de> (raw)
In-Reply-To: <20190727055638.20443-7-swood@redhat.com>
On 2019-07-27 00:56:36 [-0500], Scott Wood wrote:
> If migrate_enable() is called while a task is preparing to sleep
> (state != TASK_RUNNING), that triggers a debug check in stop_one_cpu().
> Explicitly reset state to acknowledge that we're accepting the spurious
> wakeup.
>
> Signed-off-by: Scott Wood <swood@redhat.com>
> ---
> kernel/sched/core.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 38a9a9df5638..eb27a9bf70d7 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7396,6 +7396,14 @@ void migrate_enable(void)
> unpin_current_cpu();
> preempt_lazy_enable();
> preempt_enable();
> +
> + /*
> + * Avoid sleeping with an existing non-running
> + * state. This will result in a spurious wakeup
> + * for the calling context.
> + */
> + __set_current_state(TASK_RUNNING);
Do you have an example for this? I'm not too sure if we are not using a
state by doing this. Actually we were losing it and get yelled at. We do:
|rt_spin_unlock()
|{
| rt_spin_lock_fastunlock();
| migrate_enable();
|}
So save the state as part of the locking process and lose it as part of
migrate_enable() if the CPU mask was changed. I *think* we need to
preserve that state until after the migration to the other CPU.
> sleeping_lock_inc();
> stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
> sleeping_lock_dec();
Sebastian
next prev parent reply other threads:[~2019-09-17 15:31 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-27 5:56 [RT PATCH 0/8] migrate disable fixes and performance Scott Wood
2019-07-27 5:56 ` [PATCH RT 1/8] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Scott Wood
2019-07-29 13:26 ` Steven Rostedt
2019-07-27 5:56 ` [PATCH RT 2/8] sched: __set_cpus_allowed_ptr: Check cpus_mask, not cpus_ptr Scott Wood
2019-09-17 14:57 ` Sebastian Andrzej Siewior
2019-09-17 15:23 ` Scott Wood
2019-07-27 5:56 ` [PATCH RT 3/8] sched: Remove dead __migrate_disabled() check Scott Wood
2019-07-27 5:56 ` [PATCH RT 4/8] sched: migrate disable: Protect cpus_ptr with lock Scott Wood
2019-09-26 16:39 ` Sebastian Andrzej Siewior
2019-09-26 16:52 ` Scott Wood
2019-09-27 12:19 ` Sebastian Andrzej Siewior
2019-09-27 20:02 ` Scott Wood
2019-07-27 5:56 ` [PATCH RT 5/8] sched/deadline: Reclaim cpuset bandwidth in .migrate_task_rq() Scott Wood
2019-09-17 15:10 ` Sebastian Andrzej Siewior
2019-09-27 8:11 ` Juri Lelli
2019-09-27 16:40 ` Scott Wood
2019-09-30 7:12 ` Juri Lelli
2019-09-30 16:24 ` Scott Wood
2019-10-01 8:52 ` Juri Lelli
2019-10-09 6:25 ` Scott Wood
2019-10-09 7:27 ` Juri Lelli
2019-10-09 19:12 ` Scott Wood
2019-10-10 8:18 ` Juri Lelli
2019-07-27 5:56 ` [PATCH RT 6/8] sched: migrate_enable: Set state to TASK_RUNNING Scott Wood
2019-09-17 15:31 ` Sebastian Andrzej Siewior [this message]
2019-09-17 17:54 ` Scott Wood
2019-07-27 5:56 ` [PATCH RT 7/8] sched: migrate_enable: Use select_fallback_rq() Scott Wood
2019-09-17 16:00 ` Sebastian Andrzej Siewior
2019-09-24 18:05 ` Scott Wood
2019-07-27 5:56 ` [PATCH RT 8/8] sched: Lazy migrate_disable processing Scott Wood
2019-09-17 16:50 ` Sebastian Andrzej Siewior
2019-09-17 17:06 ` Scott Wood
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