linux-kernel - Re: [PATCH -tip v4 3/3] kprobes: Support delayed unoptimization

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Message-ID: <4CEF7D92.1080207@hitachi.com>
Date:	Fri, 26 Nov 2010 18:27:46 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jason Baron <jbaron@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org, 2nddept-manager@....hitachi.co.jp,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH -tip v4 3/3] kprobes: Support delayed unoptimization

(2010/11/26 16:26), Ingo Molnar wrote:
> * Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
>> Unoptimization occurs when a probe is unregistered or disabled, and
>> is heavy because it recovers instructions by using stop_machine().
>> This patch delays unoptimization operations and unoptimize several
>> probes at once by using text_poke_smp_batch().
>> This can avoid unexpected system slowdown coming from stop_machine().
>>
>> Changes in v2:
>> - Use dynamic allocated buffers and params.
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: x86@...nel.org
>> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: linux-kernel@...r.kernel.org
>> Cc: Rusty Russell <rusty@...tcorp.com.au>
>> Cc: Frederic Weisbecker <fweisbec@...il.com>
>> ---
>>
>>  arch/x86/include/asm/kprobes.h |    4 
>>  arch/x86/kernel/kprobes.c      |   45 ++++
>>  include/linux/kprobes.h        |    2 
>>  kernel/kprobes.c               |  434 +++++++++++++++++++++++++++-------------
>>  4 files changed, 344 insertions(+), 141 deletions(-)
> 
> Hm, this is a scary big patch with non-trivial effects - it should be broken up as 
> much as possible, into successive, bisectable steps. The end result looks mostly 
> fine - it's just this one huge step of a patch that is dangerous.

Agreed, then I'll break it down to several patches.
Thank you for your comment! :)

> 
> Thanks,
> 
> 	Ingo


-- 
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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