From: Li Zefan <lizf@cn.fujitsu.com>
Date: Mon, 23 Aug 2010 08:50:12 +0000 (+0800)
Subject: tracing: Fix a race in function profile
X-Git-Tag: v2.6.36-rc4~73^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3aaba20f26f58843e8f20611e5c0b1c06954310f;p=pandora-kernel.git

tracing: Fix a race in function profile

While we are reading trace_stat/functionX and someone just
disabled function_profile at that time, we can trigger this:

	divide error: 0000 [#1] PREEMPT SMP
	...
	EIP is at function_stat_show+0x90/0x230
	...

This fix just takes the ftrace_profile_lock and checks if
rec->counter is 0. If it's 0, we know the profile buffer
has been reset.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: stable@kernel.org
LKML-Reference: <4C723644.4040708@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

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