From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751562AbWGYU1r (ORCPT ); Tue, 25 Jul 2006 16:27:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751564AbWGYU1q (ORCPT ); Tue, 25 Jul 2006 16:27:46 -0400 Received: from atlrel8.hp.com ([156.153.255.206]:33710 "EHLO atlrel8.hp.com") by vger.kernel.org with ESMTP id S1751562AbWGYU1p (ORCPT ); Tue, 25 Jul 2006 16:27:45 -0400 Date: Tue, 25 Jul 2006 13:18:45 -0700 From: Stephane Eranian To: Chuck Ebbert <76306.1226@compuserve.com> Cc: linux-kernel , Linus Torvalds , Andi Kleen Subject: Re: [PATCH] i386 TIF flags for debug regs and io bitmap in ctxsw (v2) Message-ID: <20060725201845.GH19928@frankl.hpl.hp.com> Reply-To: eranian@hpl.hp.com References: <200607251522_MC3-1-C616-70EB@compuserve.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200607251522_MC3-1-C616-70EB@compuserve.com> User-Agent: Mutt/1.4.1i Organisation: HP Labs Palo Alto Address: HP Labs, 1U-17, 1501 Page Mill road, Palo Alto, CA 94304, USA. E-mail: eranian@hpl.hp.com Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Chuck, On Tue, Jul 25, 2006 at 03:19:49PM -0400, Chuck Ebbert wrote: > > > As for TIF_DEBUG, my patch is not clearing it. I don't think you can > > have HW breakpoints be inherited from one task to the other. > > Looks like the debug regs get copied on fork and only cleared on exec > in flush_thread(). So this should be OK. Please doublecheck. > How is this supposed to work? You can set debug registers via ptrace(). So A is ptracing B and sets up breakpoints in B. Now, if B forks C, C inherits the breakpoints of B. But what about the ptracing and re-parenting that is associated with this? If A does not know about C, I wonder how this could be work and be useful? > (The new TIF_DEBUG flag went into 2.8.18-rc, in case you didn't notice.) I did not keep track but thanks or this update. That's great! -- -Stephane