linux-kernel - RE: kdump: crash_kexec()-smp_send

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Message-ID: <5C4C569E8A4B9B42A84A977CF070A35B2C57612A37@USINDEVS01.corp.hds.com>
Date:	Mon, 24 Oct 2011 18:24:14 -0400
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Vivek Goyal <vgoyal@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Américo Wang <xiyou.wangcong@...il.com>,
	"holzheu@...ux.vnet.ibm.com" <holzheu@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
	"heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: kdump: crash_kexec()-smp_send_stop() race in panic

Hi,

>> >>> 1st CPU:
>> >>> panic()->crash_kexec()->mutex_trylock(&kexec_mutex)-> do kdump
>> >>>
>> >>> 2nd CPU:
>> >>> panic()->crash_kexec()->kexec_mutex already held by 1st CPU
>> >>>        ->smp_send_stop()-> stop CPU 1 (stop kdump)
>> >>>
>> >>> How should we fix this problem? One possibility could be to do
>> >>> smp_send_stop() before we call crash_kexec().

http://lkml.org/lkml/2010/9/16/353

I developed a patch solving this issue one year ago.
(Just adding local_irq_disable in kexec path.)

I hope this helps.

Seiji

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