linux-kernel - Re: BUG - function tracing with breakpoints

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Message-ID: <4FBFC421.3020901@linux.intel.com>
Date:	Fri, 25 May 2012 10:40:49 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: BUG - function tracing with breakpoints

On 05/25/2012 08:29 AM, Steven Rostedt wrote:
> 
> This would make sense for this bug, as if modifying_ftrace_code was not
> seen by other CPUs, it wouldn't go into the ftrace_int3_handler() path.
> That would cause this issue. But the bug remains after the smp_mb()'s
> were put in place. Although it behaves a little differently not. Maybe
> there's something else I missed?
> 

Perhaps you should make the modifying_ftrace_code modification atomic...
it seems odd to have it not be atomic when it is clearly accessed across
CPUs that way.

	-hpa


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