linux-kernel - Re: race condition in schedule_on_each

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Message-ID: <51B14472.60904@kylinos.com.cn>
Date:	Fri, 07 Jun 2013 10:24:50 +0800
From:	"weiqi@...inos.com.cn" <weiqi@...inos.com.cn>
To:	Tejun Heo <tj@...nel.org>
CC:	"weiqi@...inos.com.cn" <weiqi@...inos.com.cn>,
	torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: race condition in schedule_on_each_cpu()

In the previous  message,You mentioned:


>> by the way, I'm wondering about  what's the race condition before
which  doesn't exist now


> Before the commit you originally quoted, the calling thread could be
preempted and migrated to another CPU before get_online_cpus() thus
ending up executing the function twice on the new cpu but skipping the
old one.


does this situation will happen in "Full preemption" config, on 3.0.30-rt50?







于 2013年06月07日 09:34, weiqi@...inos.com.cn 写道:
> it's preemption mode related ,
>
> on the 3.0.30-rt50, only   config kernel  with highest preemption 
> level (Fully Preemptible Kernel (RT)) in cpu preemption model
> will cause problem
>
> and even i use the "Preemptible Kernel" or "Preemptible Kernel 
> (Low-Latency Desktop)"  the problem would not happen..
>
>
> > I looked through the logs but the only worker depletion related 
> patches which pop up are around CPU hotplugs, so I don't think they 
> apply here. If the problem is relatively easy to reproduce && you 
> can't move onto a newer kernel, I'm afraid bisection probably is the 
> best option. Thanks!
>


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