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

[Masami Hiramatsu <mhiramat@redhat.com>]

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

Right.

> 
> 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@redhat.com