From: Valentin Schneider <valentin.schneider@arm.com>
To: peterz@infradead.org
Cc: mingo@kernel.org, vincent.guittot@linaro.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bristot@redhat.com, swood@redhat.com
Subject: Re: [PATCH 1/2] sched: Fix balance_callback()
Date: Fri, 11 Sep 2020 14:27:30 +0100 [thread overview]
Message-ID: <jhjpn6s5tq5.mognet@arm.com> (raw)
In-Reply-To: <20200911122547.GI1362448@hirez.programming.kicks-ass.net>
On 11/09/20 13:25, peterz@infradead.org wrote:
> On Fri, Sep 11, 2020 at 01:17:02PM +0100, Valentin Schneider wrote:
>> So that can be say __schedule() tail racing with some setprio; what's the
>> worst that can (currently) happen here? Something like say two consecutive
>> enqueuing of push_rt_tasks() to the callback list?
>
> Yeah, but that isn't in fact the case I worry most about.
>
> What can happen (and what I've spotted once before) is that someone
> attempts to enqueue a balance_callback from a rq->lock region that
> doesn't handle the calls.
>
> Currently that 'works', that is, it will get ran _eventually_. But
> ideally we'd want that to not work and issue a WARN. We want the
> callbacks to be timely.
>
> So basically all of these machinations we in order to add the WARN :-)
Makes sense, thanks!
next prev parent reply other threads:[~2020-09-11 14:12 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 8:17 [PATCH 0/2] sched: migrate_disable() preparations Peter Zijlstra
2020-09-11 8:17 ` [PATCH 1/2] sched: Fix balance_callback() Peter Zijlstra
2020-09-11 12:17 ` Valentin Schneider
2020-09-11 12:25 ` peterz
2020-09-11 13:27 ` Valentin Schneider [this message]
2020-09-11 8:17 ` [PATCH 2/2] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-09-11 12:17 ` Valentin Schneider
2020-09-11 12:29 ` peterz
2020-09-11 13:48 ` Valentin Schneider
2020-09-16 10:18 ` Sebastian Andrzej Siewior
2020-09-16 12:10 ` peterz
2020-09-16 13:58 ` Sebastian Andrzej Siewior
2020-09-16 14:07 ` peterz
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