Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757477Ab1FPJrS (ORCPT ); Thu, 16 Jun 2011 05:47:18 -0400 Received: from casper.infradead.org ([85.118.1.10]:39065 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756448Ab1FPJrR convert rfc822-to-8bit (ORCPT ); Thu, 16 Jun 2011 05:47:17 -0400 Subject: Re: [PATCH v4 3.0-rc2-tip 4/22] 4: Uprobes: register/unregister probes. From: Peter Zijlstra To: Srikar Dronamraju Cc: Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Ananth N Mavinakayanahalli , Hugh Dickins , Christoph Hellwig , Jonathan Corbet , Thomas Gleixner , Masami Hiramatsu , Oleg Nesterov , Andrew Morton , Jim Keniston , Roland McGrath , Andi Kleen , LKML In-Reply-To: <20110616041137.GG4952@linux.vnet.ibm.com> References: <20110607125804.28590.92092.sendpatchset@localhost6.localdomain6> <20110607125900.28590.16071.sendpatchset@localhost6.localdomain6> <1308159719.2171.57.camel@laptop> <20110616041137.GG4952@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 16 Jun 2011 11:46:22 +0200 Message-ID: <1308217582.15315.94.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2237 Lines: 55 On Thu, 2011-06-16 at 09:41 +0530, Srikar Dronamraju wrote: > * Peter Zijlstra [2011-06-15 19:41:59]: > > > On Tue, 2011-06-07 at 18:29 +0530, Srikar Dronamraju wrote: > > > 1. Use mm->owner and walk thro the thread_group of mm->owner, siblings > > > of mm->owner, siblings of parent of mm->owner. This should be > > > good list to traverse. Not sure if this is an exhaustive > > > enough list that all tasks that have a mm set to this mm_struct are > > > walked through. > > > > As per copy_process(): > > > > /* > > * Thread groups must share signals as well, and detached threads > > * can only be started up within the thread group. > > */ > > if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) > > return ERR_PTR(-EINVAL); > > > > /* > > * Shared signal handlers imply shared VM. By way of the above, > > * thread groups also imply shared VM. Blocking this case allows > > * for various simplifications in other code. > > */ > > if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) > > return ERR_PTR(-EINVAL); > > > > CLONE_THREAD implies CLONE_VM, but not the other way around, we > > therefore would be able to CLONE_VM and not be part of the primary > > owner's thread group. > > > > This is of course all terribly sad.. > > Agree, > > If clone(CLONE_VM) were to be done by a thread_group leader, we can walk > thro the siblings of parent of mm->owner. > > However if clone(CLONE_VM) were to be done by non thread_group_leader > thread, then we dont even seem to add it to the init_task. i.e I dont > think we can refer to such a thread even when we walk thro > do_each_thread(g,t) { .. } while_each_thread(g,t); > > right? No, we initialize p->group_leader = p; and only change that for CLONE_THREAD, so a clone without CLONE_THREAD always results in a new thread group leader, which are always added to the init_task list. Or I'm now confused, which isn't at all impossible with that code ;-) -- 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/