From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754732Ab1EWMor (ORCPT ); Mon, 23 May 2011 08:44:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55382 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754271Ab1EWMoq (ORCPT ); Mon, 23 May 2011 08:44:46 -0400 Date: Mon, 23 May 2011 14:43:14 +0200 From: Oleg Nesterov To: Tejun Heo Cc: Denys Vlasenko , jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu, bdonlan@gmail.com Subject: Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE Message-ID: <20110523124314.GA7232@redhat.com> References: <1305569849-10448-1-git-send-email-tj@kernel.org> <1305569849-10448-4-git-send-email-tj@kernel.org> <201105180240.56754.vda.linux@googlemail.com> <20110518095539.GU20624@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110518095539.GU20624@htj.dyndns.org> 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 On 05/18, Tejun Heo wrote: > > I've been thinking about Jan's suggestion to make ATTACH and DETACH > not require tracee to trap. We already have this for DETACH for cases > where the tracer is killed Yes, I still think that the new DETACH_XXX request which doesn't need the stopped tracee makes sense. Yes, we have PTRACE_INTERRUPT. But please recall the previous discussion, it is possible that the tracee can't react to PTRACE_INTERRUPT and trap because it waits for other threads we are tracing. And. Currently there is no way to detach a zombie leader. Perhaps we should change do_wait(), but it is not clear what should we do if the tracer is the real parent (we already discussed this a bit). > and it seems it wouldn't be too difficult > to make that happen for ATTACH either Yes, I think this is simple to do. Do we need this? I leave this up to you and Jan. To me personally attach-implies-trap looks more natural, but probably gdb has another opinion. Anyway. IIUC, gdb wants the auto-attach-on-clone without the trap, this is more important but this opens a lot of problems. > and for that to be truly useful > I suppose PTRACE_SETOPTIONS shouldn't require trapped state either. Hmm. Why? we could pass this options along with PTRACE_SEIZE? > Jan, would that be enough for the use cases you have on mind? Jan? Oleg.