linux-kernel - Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump patching without stop

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Message-ID: <20100118165443.GB29764@Krystal>
Date:	Mon, 18 Jan 2010 11:54:43 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, rostedt@...dmis.org,
	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, tglx@...utronix.de, andi@...stfloor.org,
	roland@...hat.com, rth@...hat.com
Subject: Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump
	patching without stop_machine

* Arjan van de Ven (arjan@...radead.org) wrote:
> On Mon, 18 Jan 2010 10:59:30 -0500
> Masami Hiramatsu <mhiramat@...hat.com> wrote:
> 
> > Yeah, so in the latest patch, I updated it to use int3 even if
> > len == 1. :-)
> > 
> 
> 
> int3 is not making a difference for your case; there is no guarantee
> that the other processor even sees the "int3 inbetween state" at all;
> if it's not safe without int3 then it won't be safe with int3 either.

What Masami means is that he updated his patch to use the int3+IPI
broadcast scheme.

Therefore, the CPUs not seeing the int3 inbetween state will be forced
to issue a serializing instruction while the int3 is in place anyway.

Thanks,

Mathieu

> 
> 
> -- 
> Arjan van de Ven 	Intel Open Source Technology Centre
> For development, discussion and tips for power savings, 
> visit http://www.lesswatts.org

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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