Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757152Ab2BCQ6B (ORCPT ); Fri, 3 Feb 2012 11:58:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2843 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756875Ab2BCQ6A (ORCPT ); Fri, 3 Feb 2012 11:58:00 -0500 Date: Fri, 3 Feb 2012 17:51:32 +0100 From: Oleg Nesterov To: Pavel Emelyanov , Jan Kratochvil , Pedro Alves Cc: Tejun Heo , Andrew Vagin , "linux-kernel@vger.kernel.org" , Roland McGrath , Cyrill Gorcunov Subject: Re: [PATCH] ptrace: add ability to get clear_tid_address Message-ID: <20120203165132.GA5636@redhat.com> References: <1328267483-3225342-1-git-send-email-avagin@openvz.org> <20120203162519.GB805@google.com> <4F2C0F13.70709@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F2C0F13.70709@parallels.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 38 On 02/03, Pavel Emelyanov wrote: > > On 02/03/2012 08:25 PM, Tejun Heo wrote: > > On Fri, Feb 03, 2012 at 02:11:23PM +0300, Andrew Vagin wrote: > >> Zero is written at clear_tid_address, when the process exits. > >> This functionality is used by pthread_join(). > >> > >> sys_set_tid_address() changes this address for current task. > >> > >> Before this patch clear_tid_address could not be got from user space. > >> I want to dump a full state of a task, so I need this address. > >> Also I think it may be useful for debugging a multithreading program. > >> > >> I am not sure that ptrace is suitable place. It may be added in prctl, > >> but I think it's a bit useless and strange. I can't image a real > >> situation (avoid checkpointing) when a thread will want to get own > >> clear_tid_address from itself, this address is used by parent ussually. > >> > >> Signed-off-by: Andrew Vagin > > > > Ummm... this really doesn't fit in ptrace. Cyrill, why not put it > > together with other params you're exporting? > > Because there's no need for current to get this value of himself, but can > be useful for e.g. gdb. OK, perhaps this makes sense, I do not know. Jan, Pedro, do you think gdb can use PTRACE_GET_TID_ADDRESS (returns tracee->clear_child_tid) ? Oleg. -- 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/