linux-kernel - Re: [PATCH] Linux Kernel Markers 0.13 for 2.6.17

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Date:	Mon, 25 Sep 2006 19:56:17 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Martin Bligh <mbligh@...gle.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	prasanna@...ibm.com, Andrew Morton <akpm@...l.org>,
	Ingo Molnar <mingo@...e.hu>, Paul Mundt <lethal@...ux-sh.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jes Sorensen <jes@....com>, Tom Zanussi <zanussi@...ibm.com>,
	Richard J Moore <richardj_moore@...ibm.com>,
	Michel Dagenais <michel.dagenais@...ymtl.ca>,
	Christoph Hellwig <hch@...radead.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	William Cohen <wcohen@...hat.com>, ltt-dev@...fik.org,
	systemtap@...rces.redhat.com, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Karim Yaghmour <karim@...rsys.com>,
	Pavel Machek <pavel@...e.cz>, Joe Perches <joe@...ches.com>,
	"Randy.Dunlap" <rdunlap@...otime.net>,
	"Jose R. Santos" <jrs@...ibm.com>
Subject: Re: [PATCH] Linux Kernel Markers 0.13 for 2.6.17

Just as a precision :

The following sequence (please refer to the code below for local symbols
1 and 2) :

1:
preempt_disable()
call (*__mark_call_##name)(format, ## args);
preempt_enable_no_resched()
2:

is insured because :

1 is part of an inline assembly with rw dependency on __marker_sequencer
the call is surrounded by memory barriers.
2 is part of an inline assembly with rw dependency on __marker_sequencer

Mathieu

* Mathieu Desnoyers (compudj@...stal.dyndns.org) wrote:
> +++ b/include/asm-generic/marker.h
> @@ -0,0 +1,22 @@
> +/*
> + * marker.h
> + *
> + * Code markup for dynamic and static tracing. Generic header.
> + * 
> + * This file is released under the GPLv2.
> + * See the file COPYING for more details.
> + */
> +
> +#define MARK_CALL(name, format, args...) \
> +	do { \
> +		static marker_probe_func *__mark_call_##name = \
> +					__mark_empty_function; \
> +		asm volatile(	".section .markers, \"a\";\n\t" \
> +				".long %1, %2;\n\t" \
> +				".previous;\n\t" : "+m" (__marker_sequencer) : \
> +			"m" (__mark_call_##name), \
> +			"m" (*format)); \
> +		preempt_disable(); \
> +		(*__mark_call_##name)(format, ## args); \
> +		preempt_enable_no_resched(); \
> +	} while(0)

> --- /dev/null
> +++ b/include/asm-i386/marker.h
> @@ -0,0 +1,30 @@
> +/*
> + * marker.h
> + *
> + * Code markup for dynamic and static tracing. i386 architecture optimisations.
> + *
> + * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> + *
> + * This file is released under the GPLv2.
> + * See the file COPYING for more details.
> + */
> +
> +#include <asm-generic/marker.h>
> +
> +#define ARCH_HAS_MARK_JUMP
> +
> +/* Note : max 256 bytes between over_label and near_jump */
> +#define MARK_JUMP(name, format, args...) \
> +	do { \
> +		asm volatile(	".section .markers, \"a\";\n\t" \
> +				".long 0f, 1f, 2f;\n\t" \
> +				".previous;\n\t" \
> +				".align 16;\n\t" \
> +				".byte 0xeb;\n\t" \
> +				"0:\n\t" \
> +				".byte 2f-1f;\n\t" \
> +				"1:\n\t" \
> +			: "+m" (__marker_sequencer) : ); \
> +		MARK_CALL(name, format, ## args); \
> +		asm volatile (	"2:\n\t" : "+m" (__marker_sequencer) : ); \
> +	} while(0)
OpenPGP public key:              http://krystal.dyndns.org:8080/key/compudj.gpg
Key fingerprint:     8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68 
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