Date: Fri, 16 Feb 2007 18:38:25 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Karim Yaghmour <karim.yaghmour@kryptiva.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Christoph Hellwig <hch@infradead.org>, Ingo Molnar <mingo@redhat.com>,
       systemtap@sources.redhat.com, ltt-dev@shafik.org
Subject: Re: [PATCH 05/05] Linux Kernel Markers, non optimized architectures
Message-ID: <20070216233825.GB28087@Krystal>
References: <1171224207118-git-send-email-mathieu.desnoyers@polymtl.ca> <1171224209195-git-send-email-mathieu.desnoyers@polymtl.ca> <20070214231635.091c7169.akpm@linux-foundation.org> <20070215190919.GA31359@Krystal> <45D61361.6030200@kryptiva.com>
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* Karim Yaghmour (karim.yaghmour@kryptiva.com) wrote:
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> Mathieu Desnoyers wrote:
> > The main goal of this config option is for embedded systems which doesn't 
> support live code modification. Maybe we can put that under "embedded 
> sytems" menu ?
> 
> Not sure whether you had had other feedback on this elsewhere in
> the rest of the thread, but yes, this would make sense if the
> "embedded" angle is the only reason we need this (and not, say,
> performance, etc.) Also, having done that, maybe it would make
> some sense to have it be a "disable" rather than "enable":
> CONFIG_MARKERS_DISABLE_OPTIMIZATION?
> 

Hi Karim,

Yes, that was indeed the first way I implemented it, as a "disable"
option. One of the main thing we have to figure out before I modify this
is if we want to have the generic version of markers available in a
"forced" manner at the marker site with the GEN_MARK macro instead of
the MARK macro (this is the actual implementation). It has proven to
be useful to instrument lockdep.c irq enable/disable tracing functions.
The reason why is because they are called just before the trap handler
returns and I need it to do XMC on x86 and x86_64. It would therefore
cause a recursive trap.

I think it makes sense to have this kind of support for hard-to-instrument
sites within the marker infrastructure, but the cost is to have two
marker flavors : MARK and GEN_MARK (but really GEN_MARK is only intended
for a few sites).

Mathieu

> Karim
> 
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-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Candidate, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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