From: Peter Zijlstra <peterz@infradead.org>
To: umgwanakikbuti@gmail.com, mingo@elte.hu
Cc: ktkhai@parallels.com, rostedt@goodmis.org, juri.lelli@gmail.com,
pang.xunlei@linaro.org, oleg@redhat.com,
linux-kernel@vger.kernel.org,
"Peter Zijlstra" <peterz@infradead.org>
Subject: [RFC][PATCH 0/7] sched: balance callbacks
Date: Mon, 01 Jun 2015 15:58:18 +0200 [thread overview]
Message-ID: <20150601135818.506080835@infradead.org> (raw)
Hi,
Mike stumbled over a cute bug where the RT/DL balancing ops caused a bug.
The exact scenario is __sched_setscheduler() changing a (runnable) task from
FIFO to OTHER. In swiched_from_rt(), where we do pull_rt_task() we temporarity
drop rq->lock. This gap allows regular cfs load-balancing to step in and
migrate our.
However, check_class_changed() will happily continue with switched_to_fair()
which assumes our task is still on the old rq and makes the kernel go boom.
Instead of trying to patch this up and make things complicated; simply disallow
these methods to drop rq->lock and extend the current post_schedule stuff into
a balancing callback list, and use that.
This survives Mike's testcase for well over an hour on my ivb-ep. I've not yet
tested it on anything bigger.
next reply other threads:[~2015-06-01 14:14 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-01 13:58 Peter Zijlstra [this message]
2015-06-01 13:58 ` [RFC][PATCH 1/7] sched: Replace post_schedule with a balance callback list Peter Zijlstra
2015-06-03 4:41 ` Kamalesh Babulal
2015-06-03 7:21 ` Peter Zijlstra
2015-06-03 8:24 ` pang.xunlei
2015-06-03 8:55 ` Peter Zijlstra
2015-06-05 7:13 ` pang.xunlei
2015-06-05 7:19 ` Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 2/7] sched: Use replace normalize_task() with __sched_setscheduler() Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 3/7] sched: Allow balance callbacks for check_class_changed() Peter Zijlstra
2015-06-02 13:58 ` Kirill Tkhai
2015-06-02 14:27 ` Peter Zijlstra
2015-06-02 16:07 ` Peter Zijlstra
2015-06-02 16:27 ` Kirill Tkhai
2015-06-03 7:32 ` Peter Zijlstra
2015-06-03 10:40 ` Kirill Tkhai
2015-06-03 10:42 ` Kirill Tkhai
2015-06-03 10:45 ` Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 4/7] sched,rt: Remove return value from pull_rt_task() Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 5/7] sched,rt: Convert switched_{from,to}_rt() / prio_changed_rt() to balance callbacks Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 6/7] sched,dl: Remove return value from pull_dl_task() Peter Zijlstra
2015-06-01 13:58 ` [RFC][PATCH 7/7] sched,dl: Convert switched_{from,to}_dl() / prio_changed_dl() to balance callbacks Peter Zijlstra
2015-06-03 4:52 ` Kamalesh Babulal
2015-06-01 14:16 ` [RFC][PATCH 0/7] sched: " Peter Zijlstra
2015-06-01 14:42 ` Mike Galbraith
2015-06-02 6:48 ` Mike Galbraith
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