linux-kernel - Re: linux-next: add utrace tree

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Date:	Wed, 27 Jan 2010 03:04:58 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Tom Tromey <tromey@...hat.com>,
	Kyle Moffett <kyle@...fetthome.net>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-next@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	utrace-devel@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
	JimKeniston <jkenisto@...ibm.com>
Subject: Re: linux-next: add utrace tree



On Wed, 27 Jan 2010, Peter Zijlstra wrote:
> 
> Right, so there's two aspects:
> 
>  1) concurrency when inserting the probe

That's the one I worried about. Stopping all threads will fix it, 
obviously at a disastrous performance cost, but what do I care? As noted, 
there are ways to do it safely with TLB switching, so it's fixable.

>  2) concurrency when hitting the probe

Yeah, I didn't worry about this part, since the only solution is the 
out-of-line one, and I don't much care how the memory gets allocated for 
it. Inserting a whole new vma seems pretty drastic, but compared to 
stopping all threads, it's a small thing.

		Linus
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