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

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Message-ID: <20090302105500.569e1270@infradead.org>
Date:	Mon, 2 Mar 2009 10:55:00 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	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>,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC][PATCH] x86: make text_poke() atomic

On Mon, 2 Mar 2009 13:36:17 -0500
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> * Arjan van de Ven (arjan@...radead.org) 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 ;(



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