From: Peter Zijlstra <peterz@infradead.org>
To: umgwanakikbuti@gmail.com, mingo@elte.hu
Cc: ktkhai@parallels.com, rostedt@goodmis.org, tglx@linutronix.de,
juri.lelli@gmail.com, pang.xunlei@linaro.org, oleg@redhat.com,
wanpeng.li@linux.intel.com, linux-kernel@vger.kernel.org,
peterz@infradead.org
Subject: [PATCH 0/9] sched: balance callbacks
Date: Wed, 03 Jun 2015 15:29:03 +0200 [thread overview]
Message-ID: <20150603132903.203333087@infradead.org> (raw)
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 task.
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.
Changes since -v1:
- make SMP=n build,
- cured switched_from_dl()'s cancel_dl_timer().
no real tests on the new parts other than booting.
next reply other threads:[~2015-06-03 13:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-03 13:29 Peter Zijlstra [this message]
2015-06-03 13:29 ` [PATCH 1/9] sched: Replace post_schedule with a balance callback list Peter Zijlstra
2015-06-03 13:29 ` [PATCH 2/9] sched: Use replace normalize_task() with __sched_setscheduler() Peter Zijlstra
2015-06-03 13:29 ` [PATCH 3/9] sched: Allow balance callbacks for check_class_changed() Peter Zijlstra
2015-06-03 13:29 ` [PATCH 4/9] sched,rt: Remove return value from pull_rt_task() Peter Zijlstra
2015-06-03 13:29 ` [PATCH 5/9] sched,rt: Convert switched_{from,to}_rt() / prio_changed_rt() to balance callbacks Peter Zijlstra
2015-06-03 13:29 ` [PATCH 6/9] sched,dl: Remove return value from pull_dl_task() Peter Zijlstra
2015-06-03 13:29 ` [PATCH 7/9] sched,dl: Convert switched_{from,to}_dl() / prio_changed_dl() to balance callbacks Peter Zijlstra
2015-06-03 13:29 ` [PATCH 8/9] hrtimer: Allow hrtimer::function() to free the timer Peter Zijlstra
2015-06-03 16:26 ` Kirill Tkhai
2015-06-03 21:13 ` Peter Zijlstra
2015-06-04 9:07 ` Kirill Tkhai
2015-06-04 10:49 ` Peter Zijlstra
2015-06-04 10:55 ` Peter Zijlstra
2015-06-04 10:58 ` Peter Zijlstra
2015-06-05 9:02 ` Kirill Tkhai
2015-06-05 9:03 ` Kirill Tkhai
2015-06-05 9:11 ` Peter Zijlstra
2015-06-05 9:10 ` Peter Zijlstra
2015-06-05 9:27 ` Kirill Tkhai
2015-06-03 17:41 ` Thomas Gleixner
2015-06-03 21:29 ` Peter Zijlstra
2015-06-04 5:59 ` Ingo Molnar
2015-06-04 10:07 ` Peter Zijlstra
2015-06-04 12:37 ` Ingo Molnar
2015-06-03 13:29 ` [PATCH 9/9] sched,dl: Fix sched class hopping CBS hole Peter Zijlstra
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