linux-kernel - Re: [patch] kprobes: optimize branch placement

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Message-Id: <20060916155522.4d493363.akpm@osdl.org>
Date:	Sat, 16 Sep 2006 15:55:22 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Jes Sorensen <jes@....com>,
	Roman Zippel <zippel@...ux-m68k.org>, tglx@...utronix.de,
	karim@...rsys.com, Paul Mundt <lethal@...ux-sh.org>,
	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Tom Zanussi <zanussi@...ibm.com>, ltt-dev@...fik.org,
	Michel Dagenais <michel.dagenais@...ymtl.ca>
Subject: Re: [patch] kprobes: optimize branch placement

On Sat, 16 Sep 2006 22:29:39 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> --- linux.orig/arch/i386/kernel/kprobes.c
> +++ linux/arch/i386/kernel/kprobes.c
> @@ -220,7 +220,7 @@ int __kprobes kprobe_handler(struct pt_r
>  	kcb = get_kprobe_ctlblk();
>  
>  	/* Check we're not actually recursing */
> -	if (kprobe_running()) {
> +	if (unlikely(kprobe_running())) {
>  		p = get_kprobe(addr);

This function does two calls to get_kprobe() (in the recurring-trap case)
where only one is needed.
-
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