From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756495Ab1FUNSz (ORCPT ); Tue, 21 Jun 2011 09:18:55 -0400 Received: from casper.infradead.org ([85.118.1.10]:41169 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752247Ab1FUNSy convert rfc822-to-8bit (ORCPT ); Tue, 21 Jun 2011 09:18:54 -0400 Subject: Re: [PATCH v4 3.0-rc2-tip 7/22] 7: uprobes: mmap and fork hooks. From: Peter Zijlstra To: Srikar Dronamraju Cc: Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Andi Kleen , Hugh Dickins , Christoph Hellwig , Jonathan Corbet , Thomas Gleixner , Masami Hiramatsu , Oleg Nesterov , LKML , Jim Keniston , Roland McGrath , Ananth N Mavinakayanahalli , Andrew Morton In-Reply-To: <1308303665.2355.11.camel@twins> References: <20110607125804.28590.92092.sendpatchset@localhost6.localdomain6> <20110607125931.28590.12362.sendpatchset@localhost6.localdomain6> <1308161486.2171.61.camel@laptop> <20110616032645.GF4952@linux.vnet.ibm.com> <1308225626.13240.34.camel@twins> <20110616130012.GL4952@linux.vnet.ibm.com> <1308248588.13240.267.camel@twins> <20110617045000.GM4952@linux.vnet.ibm.com> <1308297836.13240.380.camel@twins> <20110617090504.GN4952@linux.vnet.ibm.com> <1308303665.2355.11.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Tue, 21 Jun 2011 15:17:23 +0200 Message-ID: <1308662243.26237.144.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 On Fri, 2011-06-17 at 11:41 +0200, Peter Zijlstra wrote: > > On thing I was thinking of to fix that initial problem of spurious traps > was to leave the uprobe in the tree but skip all probes without > consumers in mmap_uprobe(). Can you find fault with using __unregister_uprobe() as a cleanup path for __register_uprobe() so that we do a second vma-rmap walk, and ignoring empty probes on uprobe_mmap()? We won't get spurious traps because the empty (no consumers) uprobe is still in the tree, we won't get any 'lost' probe insn because the cleanup does a second vma-rmap walk which will include the new mmap(). And double probe insertion is harmless. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 0909190013A for ; Tue, 21 Jun 2011 09:18:29 -0400 (EDT) Subject: Re: [PATCH v4 3.0-rc2-tip 7/22] 7: uprobes: mmap and fork hooks. From: Peter Zijlstra In-Reply-To: <1308303665.2355.11.camel@twins> References: <20110607125804.28590.92092.sendpatchset@localhost6.localdomain6> <20110607125931.28590.12362.sendpatchset@localhost6.localdomain6> <1308161486.2171.61.camel@laptop> <20110616032645.GF4952@linux.vnet.ibm.com> <1308225626.13240.34.camel@twins> <20110616130012.GL4952@linux.vnet.ibm.com> <1308248588.13240.267.camel@twins> <20110617045000.GM4952@linux.vnet.ibm.com> <1308297836.13240.380.camel@twins> <20110617090504.GN4952@linux.vnet.ibm.com> <1308303665.2355.11.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 21 Jun 2011 15:17:23 +0200 Message-ID: <1308662243.26237.144.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 , Andi Kleen , Hugh Dickins , Christoph Hellwig , Jonathan Corbet , Thomas Gleixner , Masami Hiramatsu , Oleg Nesterov , LKML , Jim Keniston , Roland McGrath , Ananth N Mavinakayanahalli , Andrew Morton On Fri, 2011-06-17 at 11:41 +0200, Peter Zijlstra wrote: >=20 > On thing I was thinking of to fix that initial problem of spurious traps > was to leave the uprobe in the tree but skip all probes without > consumers in mmap_uprobe(). Can you find fault with using __unregister_uprobe() as a cleanup path for __register_uprobe() so that we do a second vma-rmap walk, and ignoring empty probes on uprobe_mmap()? We won't get spurious traps because the empty (no consumers) uprobe is still in the tree, we won't get any 'lost' probe insn because the cleanup does a second vma-rmap walk which will include the new mmap(). And double probe insertion is harmless. -- 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