linux-kernel - Re: [PATCH RT] sched: Prevent task state corruption by spurious lock wakeup

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Date:   Tue, 6 Jun 2017 14:16:38 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
cc:     linux-rt-users <linux-rt-users@...r.kernel.org>,
        Sebastian Sewior <bigeasy@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mathias Koehrer <mathias.koehrer@...s.com>,
        David Hauck <davidh@...acquire.com>
Subject: Re: [PATCH RT] sched: Prevent task state corruption by spurious lock
 wakeup

On Sat, 3 Jun 2017, Thomas Gleixner wrote:
> If the to be woken task has state TASK_TRACED then the wakeup state check
> should not match. But for some stupid reason wake_up_lock_sleeper() should
> not use TASK_ALL. The lock sleepers are in state UNINTERRUPTIBLE, so the
> wake state should be UNINTERRUPTIBLE as well.
> 
> The extra check in try_to_wake_up() should stay though as it prevents
> spurious wake ups in general.

Further experimentation shows that it's not worth it. I'll send a V2 of
that patch with the proper fix.

Thanks,

	tglx