From: Daniel Bristot de Oliveira <daniel@bristot.me>
To: Steven Rostedt <rostedt@goodmis.org>, Christoph Lameter <cl@linux.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature
Date: Mon, 7 Nov 2016 19:49:03 +0100 [thread overview]
Message-ID: <47238aa4-cc41-96ac-4d6e-c182a340db85@bristot.me> (raw)
In-Reply-To: <20161107133207.4282de69@gandalf.local.home>
On 11/07/2016 07:32 PM, Steven Rostedt wrote:
>> Excellent this would improve the situation with deadlocks as a result of
>> > cgroup_locks not being released due to lack of workqueue processing.
> ?? What deadlocks do you see? I mean, can you show the situation that
> throttling RT tasks will cause deadlock?
>
> Sorry, but I'm just not seeing it.
It is not a deadlock in the theoretical sense of the word, but it is
more a side effect of the starvation - that looks like a deadlock.
There is a case where the removal of a cgroup dir calls
lru_add_drain_all(), that might schedule a kworker in the CPU that is
running the spinning-rt task. The kworker will starve - because they are
SCHED_OTHER by design, the lru_add_drain_all() will wait forever while
holding the cgroup lock and this will cause a lot of problems on other
tasks.
This problem was fixed on -rt using a -rt specific lock mechanism, but
the problem still exist in the non-rt kernel. Btw, this is just an
example of side effects of the starvation of non-rt-tasks. We can have
more examples...
-- Daniel
next prev parent reply other threads:[~2016-11-07 18:49 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-07 8:17 [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira
2016-11-07 10:31 ` Tommaso Cucinotta
2016-11-07 13:51 ` Daniel Bristot de Oliveira
2016-11-07 18:03 ` Tommaso Cucinotta
2016-11-07 18:06 ` Luca Abeni
2016-11-08 7:55 ` luca abeni
2016-11-08 10:30 ` Juri Lelli
2016-11-07 16:55 ` Christoph Lameter
2016-11-07 18:32 ` Steven Rostedt
2016-11-07 18:49 ` Daniel Bristot de Oliveira [this message]
2016-11-07 19:16 ` Steven Rostedt
2016-11-07 19:30 ` Christoph Lameter
2016-11-07 19:47 ` Steven Rostedt
2016-11-07 19:54 ` Christoph Lameter
2016-11-07 20:00 ` Steven Rostedt
2016-11-07 20:06 ` Daniel Bristot de Oliveira
2016-11-07 20:16 ` Steven Rostedt
2016-11-07 20:33 ` Daniel Bristot de Oliveira
2016-11-07 20:44 ` Steven Rostedt
2016-11-08 9:22 ` [PATCH] sched/rt: Change default setup for RT THROTTLING Daniel Bristot de Oliveira
2016-11-08 23:42 ` [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter
2016-11-07 18:22 ` Clark Williams
2016-11-07 18:30 ` Steven Rostedt
2016-11-07 18:38 ` Daniel Bristot de Oliveira
2016-11-07 18:39 ` Clark Williams
2016-11-08 11:59 ` Peter Zijlstra
2016-11-08 14:07 ` Steven Rostedt
2016-11-08 16:51 ` Peter Zijlstra
2016-11-08 17:17 ` Steven Rostedt
2016-11-08 18:05 ` Peter Zijlstra
2016-11-08 19:29 ` Daniel Bristot de Oliveira
2016-11-08 19:50 ` Peter Zijlstra
2016-11-09 13:33 ` Daniel Bristot de Oliveira
[not found] ` <CAA7rmPF0nQb9721MQWurRCy7E3X46hAy2qV=joK=z5U-t70NOg@mail.gmail.com>
2016-11-11 18:46 ` Christoph Lameter
2016-11-11 22:53 ` Peter Zijlstra
2016-11-13 18:53 ` Christoph Lameter
2016-11-14 9:20 ` Peter Zijlstra
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