| From: |
| Peter Zijlstra <peterz@infradead.org> |
| To: |
| umgwanakikbuti@gmail.com, mingo@elte.hu |
| Subject: |
| [PATCH 00/14] sched: balance callbacks |
| Date: |
| Fri, 05 Jun 2015 10:48:36 +0200 |
| Message-ID: |
| <20150605084836.364306429@infradead.org> |
| 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 |
| Archive‑link: | |
Article |
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 -v2:
- reworked the hrtimer patch. -- Kirill, tglx
- added lock pinning
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 / building kernels.
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