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

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Message-ID: <877hr4g49l.fsf@basil.nowhere.org>
Date:	Tue, 26 Jan 2010 18:33:26 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	tromey@...hat.com
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Kyle Moffett <kyle@...fetthome.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Peter Zijlstra <peterz@...radead.org>,
	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,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: linux-next: add utrace tree

Tom Tromey <tromey@...hat.com> writes:

> * Use an fd, not SIGCHLD+wait, to report inferior state changes to gdb.
>   Internally we're already using a self-pipe to integrate this into
>   gdb's main loop.  Relatedly, don't mess with the inferior's parentage.

How would having a kernel based solution be better over your
user space simulation?

BTW there's the new signalfd() system call that might do it
(haven't checked if it works for SIGCHLD)

> * Support "displaced stepping" in the kernel; I think this would improve
>   performance when debugging in non-stop mode.

Not sure what "displaced stepping" is exactly, but it 
sounds like the branch tracing extensions that got added a 
few releases ago? On modern Intel chips they give you a branch
buffer in memory.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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