From: Peter Zijlstra <peterz@infradead.org>
To: xlpang@redhat.com
Cc: Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, Juri Lelli <juri.lelli@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline tasks
Date: Sat, 9 Apr 2016 15:29:35 +0200 [thread overview]
Message-ID: <20160409132935.GU3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <57087633.3020700@redhat.com>
On Sat, Apr 09, 2016 at 11:25:39AM +0800, Xunlei Pang wrote:
> > In any case, I just realized we do not in fact provide this guarantee
> > (of pointing to a blocked task) that needs a bit more work.
>
> Current patch calls rt_mutex_adjust_prio() before wake_up_q() the
> wakee, at that moment the wakee has been removed by
> rt_mutex_slowunlock()->mark_wakeup_next_waiter(), from current's
> pi_waiters, rt_mutex_adjust_prio() won't see this wakee, so I think
> this should not be problem.
No, any wakeup after mark_wakeup_next_waiter() will make the task run.
And since we must always consider spurious wakeups, we cannot rely on us
(eg. our wake_up_q call) being the one and only.
Therefore it is possible and the only thing that stands between us and
doom is the fact that the wake_q stuff holds a task reference.
But we cannot guarantee that the task we have a pointer to is in fact
blocked.
next prev parent reply other threads:[~2016-04-09 13:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 11:00 [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline tasks Xunlei Pang
2016-04-01 11:38 ` Peter Zijlstra
2016-04-01 12:23 ` Xunlei Pang
2016-04-01 13:12 ` Peter Zijlstra
2016-04-01 13:34 ` Xunlei Pang
2016-04-01 21:51 ` Peter Zijlstra
2016-04-02 10:19 ` Xunlei Pang
2016-04-05 8:38 ` Xunlei Pang
2016-04-05 9:19 ` Peter Zijlstra
2016-04-05 9:29 ` Peter Zijlstra
2016-04-05 10:48 ` Xunlei Pang
2016-04-05 11:32 ` Peter Zijlstra
2016-04-08 16:25 ` Steven Rostedt
2016-04-08 17:38 ` Peter Zijlstra
2016-04-08 18:50 ` Steven Rostedt
2016-04-08 18:59 ` Peter Zijlstra
2016-04-08 19:15 ` Steven Rostedt
2016-04-08 19:28 ` Steven Rostedt
2016-04-09 3:27 ` Xunlei Pang
2016-04-09 3:25 ` Xunlei Pang
2016-04-09 13:29 ` Peter Zijlstra [this message]
2016-04-10 8:22 ` Xunlei Pang
2016-04-12 3:08 ` Xunlei Pang
2016-04-12 15:51 ` Peter Zijlstra
2016-04-13 2:13 ` Xunlei Pang
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