linux-kernel - Re: [PATCH 05/14] hrtimer: Fix invalid wakeup in do

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Message-ID: <alpine.DEB.2.02.1309121527320.4089@ionos.tec.linutronix.de>
Date:	Thu, 12 Sep 2013 15:33:48 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Libin <huawei.libin@...wei.com>
cc:	akpm@...ux-foundation.org, tj@...nel.org, viro@...iv.linux.org.uk,
	eparis@...hat.com, rusty@...tcorp.com.au, ebiederm@...ssion.com,
	paulmck@...ux.vnet.ibm.com, john.stultz@...aro.org,
	mingo@...hat.com, peterz@...radead.org, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, lizefan@...wei.com,
	jovi.zhangwei@...wei.com, guohanjun@...wei.com,
	zhangdianfang@...wei.com, wangyijing@...wei.com
Subject: Re: [PATCH 05/14] hrtimer: Fix invalid wakeup in do_nanosleep

On Thu, 29 Aug 2013, Libin wrote:

> If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE),
> and the other thread set the condition followed with wake_up_process. After
> that when this thread is re-scheduled, calling set_current_state to set itself
> as state TASK_INTERRUPTIBLE, if it is preempted again after that and before
> __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.

do_nanosleep() is only called from sys_nanosleep() and
sys_clock_nanosleep() user space interfaces.

So the task is not going to be woken up by some magic other thread
except by a signal. The latter is handled by the scheduler which will
return with state running. So what kind of problem are you trying to
solve?

Thanks,

	tglx



 
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