From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161010AbXAEMSo (ORCPT ); Fri, 5 Jan 2007 07:18:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965139AbXAEMSo (ORCPT ); Fri, 5 Jan 2007 07:18:44 -0500 Received: from ug-out-1314.google.com ([66.249.92.168]:56672 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965101AbXAEMSn (ORCPT ); Fri, 5 Jan 2007 07:18:43 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:date:from:to:cc:subject:message-id:references:mime-version:content-type:content-disposition:in-reply-to:user-agent:sender; b=oRLoNdlMO8LFSfz1hNQniCP2W8j6OdlPo0PEFmeGFIcBFEAhQsiIILh1EuunAGt8IHnMiSP6CDARwwGrI9IO5vbsKUTrSvQlotXyra6qOFzsigjWYe9IqJ/tlfXmp5RPLqYQ/NorHoH5/ICQ4QnUVlS6MpOI2pKLeaeZjzOBTQM= Date: Fri, 5 Jan 2007 12:16:43 +0000 From: Frederik Deweerdt To: Andrew Morton Cc: linux-kernel@vger.kernel.org, greg@kroah.com, maneesh@in.ibm.com, oliver@neukum.name Subject: [-mm patch] lockdep: possible deadlock in sysfs Message-ID: <20070105121643.GE17863@slug> References: <20070104220200.ae4e9a46.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070104220200.ae4e9a46.akpm@osdl.org> User-Agent: mutt-ng/devel-r804 (Linux) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 04, 2007 at 10:02:00PM -0800, Andrew Morton wrote: > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc3/2.6.20-rc3-mm1/ > Hi, Lockdep issues the following warning: [ 9.064000] ============================================= [ 9.064000] [ INFO: possible recursive locking detected ] [ 9.064000] 2.6.20-rc3-mm1 #3 [ 9.064000] --------------------------------------------- [ 9.064000] init/1 is trying to acquire lock: [ 9.064000] (&sysfs_inode_imutex_key){--..}, at: [] mutex_lock+0x1c/0x1f [ 9.064000] [ 9.064000] but task is already holding lock: [ 9.064000] (&sysfs_inode_imutex_key){--..}, at: [] mutex_lock+0x1c/0x1f [ 9.065000] [ 9.065000] other info that might help us debug this: [ 9.065000] 2 locks held by init/1: [ 9.065000] #0: (tty_mutex){--..}, at: [] mutex_lock+0x1c/0x1f [ 9.065000] #1: (&sysfs_inode_imutex_key){--..}, at: [] mutex_lock+0x1c/0x1f [ 9.065000] [ 9.065000] stack backtrace: [ 9.065000] [] show_trace_log_lvl+0x1a/0x30 [ 9.066000] [] show_trace+0x12/0x14 [ 9.066000] [] dump_stack+0x16/0x18 [ 9.066000] [] print_deadlock_bug+0xb9/0xc3 [ 9.066000] [] check_deadlock+0x55/0x5a [ 9.066000] [] __lock_acquire+0x371/0xbf0 [ 9.066000] [] lock_acquire+0x69/0x83 [ 9.066000] [] __mutex_lock_slowpath+0x75/0x2d1 [ 9.066000] [] mutex_lock+0x1c/0x1f [ 9.066000] [] sysfs_drop_dentry+0xb1/0x133 [ 9.066000] [] sysfs_hash_and_remove+0xb3/0x142 [ 9.066000] [] sysfs_remove_file+0xd/0x10 [ 9.067000] [] device_remove_file+0x23/0x2e [ 9.067000] [] device_del+0x188/0x1e6 [ 9.067000] [] device_unregister+0xb/0x15 [ 9.067000] [] device_destroy+0x9c/0xa9 [ 9.067000] [] vcs_remove_sysfs+0x1c/0x3b [ 9.067000] [] con_close+0x5e/0x6b [ 9.067000] [] release_dev+0x4c4/0x6e5 [ 9.067000] [] tty_release+0x12/0x1c [ 9.067000] [] __fput+0x177/0x1a0 [ 9.067000] [] fput+0x3b/0x41 [ 9.068000] [] filp_close+0x36/0x65 [ 9.068000] [] sys_close+0x63/0xa4 [ 9.068000] [] sysenter_past_esp+0x5f/0x99 [ 9.068000] ======================= This is due to sysfs_hash_and_remove() holding dir->d_inode->i_mutex before calling sysfs_drop_dentry() which calls orphan_all_buffers() which in turn takes node->i_mutex. The following patch solves the problem by defering the buffers orphaning after the dir->d_inode->imutex is released. Not sure it's the best solution though, better wait for feedback from Maneesh and Oliver. (This is mostly a resend of the patch that I sent for 2.6.20-rc2-mm1 [1], but it adds the initialisation of inode in sysfs_hash_and_remove) Regards, Frederik [1] http://groups.google.com/group/linux.kernel/msg/5164f76c31958e0b?dmode=source Signed-off-by: Frederik Deweerdt diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c index 8c533cb..bcf6bc0 100644 --- a/fs/sysfs/inode.c +++ b/fs/sysfs/inode.c @@ -230,10 +230,10 @@ static inline void orphan_all_buffers(struct inode *node) * Unhashes the dentry corresponding to given sysfs_dirent * Called with parent inode's i_mutex held. */ -void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent) +struct inode *sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent) { struct dentry * dentry = sd->s_dentry; - struct inode *inode; + struct inode *inode = NULL; if (dentry) { spin_lock(&dcache_lock); @@ -248,19 +248,19 @@ void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent) spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); simple_unlink(parent->d_inode, dentry); - orphan_all_buffers(inode); - iput(inode); } else { spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); } } + return inode; } int sysfs_hash_and_remove(struct dentry * dir, const char * name) { struct sysfs_dirent * sd; struct sysfs_dirent * parent_sd; + struct inode *inode = NULL; int found = 0; if (!dir) @@ -277,7 +277,7 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name) continue; if (!strcmp(sysfs_get_name(sd), name)) { list_del_init(&sd->s_sibling); - sysfs_drop_dentry(sd, dir); + inode = sysfs_drop_dentry(sd, dir); sysfs_put(sd); found = 1; break; @@ -285,5 +285,10 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name) } mutex_unlock(&dir->d_inode->i_mutex); + if (found && inode) { + orphan_all_buffers(inode); + iput(inode); + } + return found ? 0 : -ENOENT; } diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h index 5100a12..ef9d217 100644 --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -17,7 +17,7 @@ extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **) extern void sysfs_remove_subdir(struct dentry *); extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd); -extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent); +extern struct inode * sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent); extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr); extern struct rw_semaphore sysfs_rename_sem;