linux-kernel - Re: OOPS in perf_mmap

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Message-ID: <alpine.DEB.2.10.1305231006280.17701@vincent-weaver-1.um.maine.edu>
Date:	Thu, 23 May 2013 10:10:36 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Al Viro <viro@...iv.linux.org.uk>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	linux-kernel@...r.kernel.org, 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()


I can confirm your patch avoids the oops on my machine.

It does lead to interesting behavior if I run the sample program
multiple times (with added printfs):

vince@...e2:~$ ./perf_mmap_close_bug 
mmap1=0x7f06a6e90000
mmap2=0x7f06a6e7f000
vince@...e2:~$ ./perf_mmap_close_bug 
mmap1=0x7f878a138000
mmap2=0x7f878a127000
vince@...e2:~$ ./perf_mmap_close_bug 
mmap1=0xffffffffffffffff
Error opening fd2 Invalid argument

and then it never successfully completes again.  Is this unexpected 
behavior?  Or just a normal mmap/perf interaction that I don't understand?

Vince
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