linux-kernel - Re: OOPS in perf_mmap

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Date:	Wed, 22 May 2013 23:48:51 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Vince Weaver <vincent.weaver@...ne.edu>
cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	trinity@...r.kernel.org
Subject: Re: OOPS in perf_mmap_close()


In case anyone cares, the Oops is happening here:

    1a56:       48 c1 e8 0c             shr    $0xc,%rax
    1a5a:       48 ff c0                inc    %rax
>   1a5d:       f0 48 29 45 60          lock sub %rax,0x60(%rbp)
    1a62:       49 8b 46 40             mov    0x40(%r14),%rax

Which maps to this in perf_mmap_close() in kernel/events/core.c:

                atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);

And "user" (%rbp) is RBP: 0000000000000000, hence the problem.

I'm having trouble tracking the problem back any further as the code is a 
bit covoluted and is not commented at all.

Vince
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