linux-kernel - Re: [PATCH] ppc64 ftrace: mark data

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Message-ID: <20150520090325.GA11577@lst.de>
Date:	Wed, 20 May 2015 11:03:25 +0200
From:	Torsten Duwe <duwe@....de>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ppc64 ftrace: mark data_access callees "notrace" (pt.1)

On Tue, May 19, 2015 at 01:27:07PM +1000, Michael Ellerman wrote:
> On Mon, 2015-05-18 at 14:29 +0200, Jiri Kosina wrote:
> > 
> > ftrace already handles recursion protection by itself (depending on the 
> > per-ftrace-ops FTRACE_OPS_FL_RECURSION_SAFE flag).
> 
> OK, so I wonder why that's not working for us?

IIRC a data access fault happens just before that flag is looked at ;-)

I'm now thinking about a hybrid solution: mark the most critical functions
"notrace", especially those directly involved with MMU loading, and add
a per-thread flag to catch the not-so-obvious cases.

	Torsten

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