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Date: Wed, 20 May 2015 11:03:25 +0200
From: Torsten Duwe <duwe@lst.de>
To: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH] ppc64 ftrace: mark data_access callees "notrace" (pt.1)
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Cc: Jiri Kosina <jkosina@suse.cz>, ppc-dev <linuxppc-dev@lists.ozlabs.org>,
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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