From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id AEB176B0012 for ; Thu, 16 Jun 2011 05:47:04 -0400 (EDT) Subject: Re: [PATCH v4 3.0-rc2-tip 4/22] 4: Uprobes: register/unregister probes. From: Peter Zijlstra 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: quoted-printable Date: Thu, 16 Jun 2011 11:46:22 +0200 Message-ID: <1308217582.15315.94.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: 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 On Thu, 2011-06-16 at 09:41 +0530, Srikar Dronamraju wrote: > * Peter Zijlstra [2011-06-15 19:41:59]: >=20 > > 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, sibling= s > > > 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.=20 > >=20 > > As per copy_process(): > >=20 > > /* > > * 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); > >=20 > > /* > > * 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); > >=20 > > 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. > >=20 > > This is of course all terribly sad.. >=20 > Agree,=20 >=20 > If clone(CLONE_VM) were to be done by a thread_group leader, we can walk > thro the siblings of parent of mm->owner. >=20 > 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); >=20 > right? No, we initialize p->group_leader =3D 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org