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Re: [PATCH] Linux Kernel Markers 0.13 for 2.6.17
- From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- To: Jeremy Fitzhardinge <jeremy at goop dot org>
- Cc: Martin Bligh <mbligh at google dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, Ingo Molnar <mingo at elte dot hu>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>, Karim Yaghmour <karim at opersys dot com>, Pavel Machek <pavel at suse dot cz>, Joe Perches <joe at perches dot com>, "Randy.Dunlap" <rdunlap at xenotime dot net>, "Jose R. Santos" <jrs at us dot ibm dot com>
- Date: Tue, 26 Sep 2006 15:08:49 -0400
- Subject: Re: [PATCH] Linux Kernel Markers 0.13 for 2.6.17
- References: <20060925233349.GA2352@Krystal> <20060925235617.GA3147@Krystal> <45187146.8040302@goop.org> <20060926002551.GA18276@Krystal> <20060926004535.GA2978@Krystal> <45187C0E.1080601@goop.org> <20060926025924.GA27366@Krystal> <4518B4A0.6070509@goop.org> <20060926180414.GA10497@Krystal> <4519781D.9040503@goop.org>
* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Mathieu Desnoyers wrote:
> >Hi,
> >
> >Ok, so as far as I can see, we can only control the execution flow by
> >modifying
> >values in the output list of the asm.
> >
> >Do you think the following would work ?
> >
> >
> >#define MARK_JUMP(name, format, args...) \
> > do { \
> > char condition; \
> > asm volatile( ".section .markers, \"a\";\n\t" \
> > ".long 0f;\n\t" \
> > ".previous;\n\t" \
> > "0:\n\t" \
> > "movb $0,%1;\n\t" \
> > : "+m" (__marker_sequencer), \
> > "=r" (condition) : ); \
> > if(unlikely(condition)) { \
> > MARK_CALL(name, format, ## args); \
> > } \
> > } while(0)
> >
>
> Yep, that looks reasonable. Though you could just directly test a
> per-marker enable flag, rather than using "condition"...
>
The goal of the local variable "condition" here is that it will be forced to be
a register (=r in asm output), so there is no memory load involved (immediate
value).
I am not sure I understand your suggestion correctly.. do you mean having
a per-marker flag that would be loaded and tested at every marker site ?
Mathieu
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