Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762237AbXHHIT6 (ORCPT ); Wed, 8 Aug 2007 04:19:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756764AbXHHITn (ORCPT ); Wed, 8 Aug 2007 04:19:43 -0400 Received: from wa-out-1112.google.com ([209.85.146.183]:11641 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756754AbXHHITk (ORCPT ); Wed, 8 Aug 2007 04:19:40 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:x-enigmail-version:content-type:content-transfer-encoding; b=ufPeeWpM3yd6vVMNnK8ZRGKTxX+pJa8gRnH6p0PiViXVE+YcC78c/dUx3nYCn9y5V7B2TAlvo2QKl0dPQ/Ioti1FsCtSYfjRrx64izy+SUy+pfrURFGeSzk1tXFOwHiVoRBztrvOOeQXDdOFH1jzO0VOgGRZfLb8MCeqIEUP4ks= Message-ID: <46B97C94.8090209@gmail.com> Date: Wed, 08 Aug 2007 17:19:32 +0900 From: Tejun Heo User-Agent: Icedove 1.5.0.10 (X11/20070307) MIME-Version: 1.0 To: "Eric W. Biederman" CC: Greg KH , linux-kernel@vger.kernel.org, satyam@infradead.org, cornelia.huck@de.ibm.com, stern@rowland.harvard.edu, Linux Containers , gregkh@suse.de Subject: Re: [PATCH 12/25] sysfs: Introduce sysfs_rename_mutex References: <11860582832964-git-send-email-htejun@gmail.com> In-Reply-To: X-Enigmail-Version: 0.94.2.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 41 Hello, Eric. Eric W. Biederman wrote: > Looking carefully at the rename code we have a subtle dependency > that the structure of sysfs not change while we are performing > a rename. If the parent directory of the object we are renaming > changes while the rename is being performed nasty things could > happen when we go to release our locks. > > So introduce a sysfs_rename_mutex to prevent this highly > unlikely theoretical issue. Yeah, it's a theoretical issue. Rename/move implementation has always depended on the parent structure not changing beneath it, but it's nice to tighten up loose ends. > +DEFINE_MUTEX(sysfs_rename_mutex); Probably doesn't really matter but wouldn't a rwsem fit better? > @@ -774,7 +775,7 @@ static struct dentry *__sysfs_get_dentry(struct super_block *sb, struct sysfs_di > * down from there looking up dentry for each step. > * > * LOCKING: > - * Kernel thread context (may sleep) > + * mutex_lock(sysfs_rename_mutex) LOCKING describes what locks should be held when entering the function, so proper description would be something like... Kernel thread context, grabs sysfs_rename_mutex Thanks. -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/