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

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Message-ID: <1264414426.4283.1644.camel@laptop>
Date:	Mon, 25 Jan 2010 11:13:46 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	ananth@...ibm.com
Cc:	Ingo Molnar <mingo@...e.hu>, Kyle Moffett <kyle@...fetthome.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>, linux-next@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>, utrace-devel@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: linux-next: add utrace tree

On Mon, 2010-01-25 at 10:29 +0530, Ananth N Mavinakayanahalli wrote:
> - Extend perf; would perf then use utrace underneath? Or would one have
>   to redo some of what utrace already does for thread level control?

No, perf is about monitoring/tracing not modifying. Its about minimal
interference, the very opposite of what ptrace/utrace is about.

>>From a perf POV if you need to stop a task (changing it scheduling
state) you've lost.

Furthermore, despite the name utrace isn't about tracing at all, its a
full blown debugging infrastructure which completely multiplexes the
task state, not something perf is interested in at all.

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