Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump patchingwithout stop_machine

From: Masami Hiramatsu
Date: Mon Jan 18 2010 - 13:21:42 EST

Mathieu Desnoyers wrote:
> * Arjan van de Ven (arjan@xxxxxxxxxxxxx) wrote:
>> On Mon, 18 Jan 2010 10:59:30 -0500
>> Masami Hiramatsu <mhiramat@xxxxxxxxxx> 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.

By the way, in kprobes, we just use a text_poke() to put int3.
I assume that we'd better send IPI afterward, wouldn't it?

Thank you,

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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