linux-kernel - Re: [RFC][PATCH] x86: make text

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Message-ID: <49AC3221.4030506@zytor.com>
Date:	Mon, 02 Mar 2009 11:23:13 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
CC:	Arjan van de Ven <arjan@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC][PATCH] x86: make text_poke() atomic

Masami Hiramatsu wrote:
>>>
>>> Stop machine is not required when inserting a breakpoint. 
>>
>> that is your assumption; when I spoke with CPU architects they
>> cringed ;(
> 
> Is that true even if modifying just one-byte (like int3 insertion)
> and we don't care synchronous write(that means code modification
> effects on other processors after a while)?
> 

The problem is that he's using is as part of a sequenced series of 
steps.  The lack of synchronization comes into play there.

	-hpa

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