linux-kernel - Re: Issue with core dump

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Message-ID: <20111102113030.GE22462@linux-mips.org>
Date:	Wed, 2 Nov 2011 11:30:31 +0000
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	trisha yad <trisha1march@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-mm <linux-mm@...ck.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
	kamezawa.hiroyu@...fujitsu.com, mhocko@...e.cz,
	rientjes@...gle.com, Andrew Morton <akpm@...ux-foundation.org>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Tejun Heo <htejun@...il.com>
Subject: Re: Issue with core dump

On Wed, Nov 02, 2011 at 12:03:39PM +0530, trisha yad wrote:

> Thanks all for your answer.
> 
> In loaded embedded system the time at with code hit do_user_fault()
> and core_dump_wait() is bit
> high, I check on my  system it took 2.7 sec. so it is very much
> possible that core dump is not correct.
> It  contain global value updated.
> 
> So is it possible at time of send_signal() we can stop modification of
> faulty thread memory ?

On existing hardware it is impossible to take a consistent snapshot of a
multi-threaded application at the time of one thread faulting.

A software simulator can handle this sort of race condition but of course
this approach has other disadvantages.

  Ralf
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