From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51])
	by kanga.kvack.org (Postfix) with ESMTP id 290D36B0092
	for <linux-mm@kvack.org>; Wed, 26 Jan 2011 05:11:14 -0500 (EST)
Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20]  5: Uprobes:
 register/unregister probes.
From: Peter Zijlstra <peterz@infradead.org>
In-Reply-To: <20110126075558.GB19725@linux.vnet.ibm.com>
References: 
	 <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6>
	 <20101216095817.23751.76989.sendpatchset@localhost6.localdomain6>
	 <1295957744.28776.722.camel@laptop>
	 <20110126075558.GB19725@linux.vnet.ibm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Date: Wed, 26 Jan 2011 11:11:48 +0100
Message-ID: <1296036708.28776.1138.camel@laptop>
Mime-Version: 1.0
Sender: owner-linux-mm@kvack.org
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Christoph Hellwig <hch@infradead.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Oleg Nesterov <oleg@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, SystemTap <systemtap@sources.redhat.com>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Frederic Weisbecker <fweisbec@gmail.com>, Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
List-ID: <linux-mm.kvack.org>

On Wed, 2011-01-26 at 13:25 +0530, Srikar Dronamraju wrote:
>=20
> > > +
> > > +               list_add(&mm->uprobes_list, &tmp_list);
> > > +               mm->uprobes_vaddr =3D vma->vm_start + offset;
> > > +       }
> > > +       spin_unlock(&mapping->i_mmap_lock);
> >=20
> > Both this and unregister are racy, what is to say:
> >  - the vma didn't get removed from the mm
> >  - no new matching vma got added
> >=20
>=20
> register_uprobe, unregister_uprobe, uprobe_mmap are all synchronized by
> uprobes_mutex. So I dont see one unregister_uprobe getting thro when
> another register_uprobe is working with a vma.
>=20
> If I am missing something elementary, please explain a bit more.

afaict you're not holding the mmap_sem, so userspace can simply unmap
the vma.

--
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 policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>