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Date: Tue, 20 Apr 2010 15:54:46 +0200
Message-ID: <87r5maqleh.wl%vmayatsk@redhat.com>
From: Vitaly Mayatskikh <v.mayatskih@gmail.com>
To: Cong Wang <amwang@redhat.com>
Cc: Vitaly Mayatskikh <v.mayatskih@gmail.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Neil Horman <nhorman@tuxdriver.com>
Subject: Re: Fix OOPS in crash_kernel_shrink
In-Reply-To: <4BCDA46E.9030405@redhat.com>
References: <87iq7n8toc.wl%vmayatsk@redhat.com>
	<4BCDA46E.9030405@redhat.com>
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At Tue, 20 Apr 2010 20:56:14 +0800, Cong Wang wrote:
> 
> Vitaly Mayatskikh wrote:
> > Two "echo 0 > /sys/kernel/kexec_crash_size" OOPSes kernel. Also
> > content of this file is invalid after first shrink to zero: it shows 1
> > instead of 0.
> > 
> > This patch fixes it.
> 
> Hmmm, I certainly did tests for 'echo 0 > kexec_crash_size' when I
> worked on this, but I didn't get any oops. Can you show me the full
> oops?

Do it twice. start == end condition will work over and over, and
kernel will try to release_resource() again (and that's causes OOPS).

This scenario is unlikely to happen often (root privs, valid
crashkernel= in cmdline, dump-capture kernel not loaded), I hit it
only by chance.

-- 
wbr, Vitaly
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