Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754243Ab0A0K6r (ORCPT ); Wed, 27 Jan 2010 05:58:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751254Ab0A0K6p (ORCPT ); Wed, 27 Jan 2010 05:58:45 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:39437 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932142Ab0A0K6o (ORCPT ); Wed, 27 Jan 2010 05:58:44 -0500 Subject: Re: linux-next: add utrace tree From: Peter Zijlstra To: Linus Torvalds Cc: Tom Tromey , Kyle Moffett , "Frank Ch. Eigler" , Oleg Nesterov , Andrew Morton , Stephen Rothwell , Fr??d??ric Weisbecker , LKML , Steven Rostedt , Arnaldo Carvalho de Melo , linux-next@vger.kernel.org, "H. Peter Anvin" , utrace-devel@redhat.com, Thomas Gleixner , JimKeniston In-Reply-To: <1264589716.4283.2006.camel@laptop> References: <20100121013822.28781960.sfr@canb.auug.org.au> <20100122005147.GD22003@redhat.com> <20100121170541.7425ff10.akpm@linux-foundation.org> <20100122182827.GA13185@redhat.com> <20100122200129.GG22003@redhat.com> <20100122221348.GA4263@redhat.com> <1264575134.4283.1983.camel@laptop> <1264589716.4283.2006.camel@laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 27 Jan 2010 11:58:06 +0100 Message-ID: <1264589886.4283.2008.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 920 Lines: 21 On Wed, 2010-01-27 at 11:55 +0100, Peter Zijlstra wrote: > Right, so there's two aspects: > > 1) concurrency when inserting the probe > 2) concurrency when hitting the probe > > 1) used to be dealt with by using utrace to stop all threads in the > process and then writing the instruction. I suggested to CoW the page, > modify the instruction, set the pagetable and flush tlbs at full speed > -- the very thing you suggest here. Also, since executable maps are typically MAP_PRIVATE, you have to CoW anyway in order to modify it and I would exclude MAP_SHARED from being probable because then the modification could seep through into whatever was backing that thing. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/