linux-kernel - Re: [tip:x86/urgent] x86, trace: Fix CR2 corruption when tracing page faults

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Message-ID: <20140305073344.2f179931@gandalf.local.home>
Date:	Wed, 5 Mar 2014 07:33:44 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...nel.org, hpa@...or.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, acme@...stprotocols.net,
	seiji.aguchi@....com, jolsa@...hat.com, vincent.weaver@...ne.edu,
	tglx@...utronix.de, hpa@...ux.intel.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, trace: Fix CR2 corruption when tracing
 page faults

On Wed, 5 Mar 2014 13:25:35 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Wed, Mar 05, 2014 at 07:20:22AM -0500, Steven Rostedt wrote:
> > On Wed, 5 Mar 2014 12:14:15 +0100
> > Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > Please no! I used tracing of the do_page_fault function all the time.
> > It is very useful.
> 
> Why do you trace do_page_fault and not the __do_page_fault() function?
> do_page_fault() is a minimal wrapper which doesn't actually do all that
> much?

Then we better make sure that __do_page_fault() is never inlined.
Otherwise, it wont be available to trace.

I'm fine with adding "notrace" to do_page_fault() and to
trace_do_page_fault() as long as we also include a "noinline" to
__do_page_fault(). Would need a comment stating why that noinline is
there though.

-- Steve
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