Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757097Ab2BHSE1 (ORCPT ); Wed, 8 Feb 2012 13:04:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:25102 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751197Ab2BHSEZ (ORCPT ); Wed, 8 Feb 2012 13:04:25 -0500 Message-ID: <4F32B924.8080407@redhat.com> Date: Wed, 08 Feb 2012 18:04:20 +0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20120131 Thunderbird/10.0 MIME-Version: 1.0 To: Oleg Nesterov CC: Cyrill Gorcunov , Pavel Emelyanov , Jan Kratochvil , Tejun Heo , Andrew Vagin , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] ptrace: add ability to get clear_tid_address References: <1328267483-3225342-1-git-send-email-avagin@openvz.org> <20120203162519.GB805@google.com> <4F2C0F13.70709@parallels.com> <20120203165132.GA5636@redhat.com> <4F31848A.9070406@redhat.com> <20120207205639.GJ27437@moon> <4F31945B.5000304@redhat.com> <20120207215121.GB29773@moon> <4F326AF7.3060203@redhat.com> <20120208173103.GA20853@redhat.com> In-Reply-To: <20120208173103.GA20853@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1098 Lines: 25 On 02/08/2012 05:31 PM, Oleg Nesterov wrote: > On 02/08, Pedro Alves wrote: >> >> I just tried it. This is &pthread->tid in glibc/libpthread, so with debug >> info it's easy to figure out where to set the watchpoint manually with gdb >> without asking the kernel. Doesn't work. ptrace doesn't show any trap >> for the kernel writes. > > The tracee simply can't report this trap. it is already dead ;) and > hw breakpoint (used by ptrace) is "pinned" to the thread. Right, as I said. :-) I saw that a watchpoint trap isn't reported either for the CLONE_CHILD_SETTID case (that is, within clone, when the kernel writes the tid to the memory address passed in to the clone syscall). I wouldn't have been surprised to see the trap in userspace in either the parent or the child, though I'm not really surprised to not see it either. -- Pedro Alves -- 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/