Re: [RFC][PATCH] x86: make text_poke() atomic

[Masami Hiramatsu]

Arjan van de Ven wrote:
> On Mon, 2 Mar 2009 13:36:17 -0500
> Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote:
>
> > * Arjan van de Ven (arjan@xxxxxxxxxxxxx) wrote:
> > > > Use map_vm_area() instead of vmap() in text_poke() for avoiding
> > > > page allocation and delayed unmapping, and call
> > > > vunmap_page_range() and local_flush_tlb() directly because this
> > > > mapping is temporary and local.
> > > >
> > > > At the result of above change, text_poke() becomes atomic and can
> > > > be called from stop_machine() etc.
> > > .... but text_poke() realistically needs to call stop_machine()
> > > since you can't poke live code.... so that makes me wonder how
> > > useful this is...
> > Hi Arjan,
> >
> > 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)?

Thank you,

--
Masami Hiramatsu

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

e-mail: mhiramat@xxxxxxxxxx

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