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Date: Sat, 20 Mar 2010 05:46:52 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>,
       Jason Baron <jbaron@redhat.com>, Steven Rostedt <rostedt@goodmis.org>,
       Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <peterz@infradead.org>,
       linux-kernel@vger.kernel.org, h.mitake@gmail.com,
       Paul Mackerras <paulus@samba.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [PATCH RFC 00/11] lock monitor: Separate features related to
	lock
Message-ID: <20100320044649.GL5085@nowhere>
References: <20100317095230.GD17146@elte.hu> <4BA1C141.8050409@dcl.info.waseda.ac.jp> <20100318211633.GG5103@nowhere> <20100319010857.GC23020@Krystal> <20100319012337.GA22095@nowhere> <20100319013658.GB28456@Krystal> <20100319022659.GC22095@nowhere> <20100319024042.GB28941@Krystal> <20100319030611.GE22095@nowhere> <20100319125600.GA12211@Krystal>
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On Fri, Mar 19, 2010 at 08:56:00AM -0400, Mathieu Desnoyers wrote:
> > Sure. My doubt is: currently with the upstream version, does the
> > compiler tend to load the parameters to the stack before the branch is
> > checked? Or is this a magic that jmp labels bring for whatever reason?
> 
> Even without the static jump patching, the compiler takes care of putting the
> stack setup after the branch is checked. That worked with a standard test on a
> variable, with immediate values and should still work with asm gotos.


Ok.


 
> I already did some presentations around these question. You can refer to my OLS
> 2008 slides, where I proposed static jump patching (ancestor of the asm gotos,
> where I did the liveness analysis myself in the back of the compiler; good
> enough for a prototype ;) ). Slide 11 discusses the branch vs stack setup
> question:
> 
> http://lttng.org/files/slides/desnoyers-talk-ols2008.pdf
> 
> Even more in Sections 8.1, 8.2 and 8.3 of my thesis:
> 
> http://lttng.org/files/thesis/desnoyers-dissertation-2009-12-v27.pdf
> 
> 8.1 Kernel Markers
> 8.2 Tracepoints
> 8.3 Immediate Values


Cool. I was already keeping your thesis on hand anyway :)

Thanks.