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 9E3229000BD for ; Mon, 26 Sep 2011 07:19:26 -0400 (EDT) Subject: Re: [PATCH v5 3.1.0-rc4-tip 1/26] uprobes: Auxillary routines to insert, find, delete uprobes From: Peter Zijlstra Date: Mon, 26 Sep 2011 13:18:40 +0200 In-Reply-To: <20110920115949.25326.2469.sendpatchset@srdronam.in.ibm.com> References: <20110920115938.25326.93059.sendpatchset@srdronam.in.ibm.com> <20110920115949.25326.2469.sendpatchset@srdronam.in.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Message-ID: <1317035920.9084.84.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 Tue, 2011-09-20 at 17:29 +0530, Srikar Dronamraju wrote: > +static struct uprobe *__insert_uprobe(struct uprobe *uprobe) > +{ > + struct rb_node **p =3D &uprobes_tree.rb_node; > + struct rb_node *parent =3D NULL; > + struct uprobe *u; > + int match; > + > + while (*p) { > + parent =3D *p; > + u =3D rb_entry(parent, struct uprobe, rb_node); > + match =3D match_uprobe(uprobe, u); > + if (!match) { > + atomic_inc(&u->ref); > + return u; > + } > + > + if (match < 0) > + p =3D &parent->rb_left; > + else > + p =3D &parent->rb_right; > + > + } > + u =3D NULL; > + rb_link_node(&uprobe->rb_node, parent, p); > + rb_insert_color(&uprobe->rb_node, &uprobes_tree); > + /* get access + drop ref */ > + atomic_set(&uprobe->ref, 2); > + return u; > +}=20 If you ever want to make a 'lockless' lookup work you need to set the refcount of the new object before its fully visible, instead of after. Now much of a problem now since its fully serialized by that uprobes_treelock thing. -- 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