From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id D5FCC8D0039 for ; Tue, 15 Mar 2011 15:41:24 -0400 (EDT) Date: Tue, 15 Mar 2011 20:22:50 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH v2 2.6.38-rc8-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree. In-Reply-To: <20110315173041.GB24254@linux.vnet.ibm.com> Message-ID: References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133444.27435.50684.sendpatchset@localhost6.localdomain6> <20110315173041.GB24254@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Srikar Dronamraju Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Masami Hiramatsu , Christoph Hellwig , Ananth N Mavinakayanahalli , Andi Kleen , Oleg Nesterov , Andrew Morton , Jim Keniston , Roland McGrath , SystemTap , LKML , "Paul E. McKenney" On Tue, 15 Mar 2011, Srikar Dronamraju wrote: > * Thomas Gleixner [2011-03-15 14:38:33]: > > > +/* > > > + * Find a uprobe corresponding to a given inode:offset > > > + * Acquires treelock > > > + */ > > > +static struct uprobe *find_uprobe(struct inode * inode, loff_t offset) > > > +{ > > > + struct uprobe *uprobe; > > > + unsigned long flags; > > > + > > > + spin_lock_irqsave(&treelock, flags); > > > + uprobe = __find_uprobe(inode, offset, NULL); > > > + spin_unlock_irqrestore(&treelock, flags); > > > > What's the calling context ? Do we really need a spinlock here for > > walking the rb tree ? > > > > find_uprobe() gets called from unregister_uprobe and on probe hit from > uprobe_notify_resume. I am not sure if its a good idea to walk the tree > as and when the tree is changing either because of a insertion or > deletion of a probe. I know that you cannot walk the tree lockless except you would use some rcu based container for your probes. Though my question is more whether this needs to be a spinlock or if that could be replaced by a mutex. At least there is no reason to disable interrupts. You cannot trap into a probe from the thread in which you are installing/removing it. Thanks, tglx -- 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