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On Thu, Jan 04, 2007 at 10:02:00PM -0800, Andrew Morton wrote: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: [<c03e6afc>] mutex_lock+0x1c/0x1f [ 9.064000] [ 9.064000] but task is already holding lock: [ 9.064000] (&sysfs_inode_imutex_key){--..}, at: [<c03e6afc>] 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: [<c03e6afc>] mutex_lock+0x1c/0x1f [ 9.065000] #1: (&sysfs_inode_imutex_key){--..}, at: [<c03e6afc>] mutex_lock+0x1c/0x1f [ 9.065000] [ 9.065000] stack backtrace: [ 9.065000] [<c010390d>] show_trace_log_lvl+0x1a/0x30 [ 9.066000] [<c0103935>] show_trace+0x12/0x14 [ 9.066000] [<c0103a2f>] dump_stack+0x16/0x18 [ 9.066000] [<c0138cb8>] print_deadlock_bug+0xb9/0xc3 [ 9.066000] [<c0138d17>] check_deadlock+0x55/0x5a [ 9.066000] [<c013a953>] __lock_acquire+0x371/0xbf0 [ 9.066000] [<c013b7a9>] lock_acquire+0x69/0x83 [ 9.066000] [<c03e6b7e>] __mutex_lock_slowpath+0x75/0x2d1 [ 9.066000] [<c03e6afc>] mutex_lock+0x1c/0x1f [ 9.066000] [<c01b249c>] sysfs_drop_dentry+0xb1/0x133 [ 9.066000] [<c01b25d1>] sysfs_hash_and_remove+0xb3/0x142 [ 9.066000] [<c01b30ed>] sysfs_remove_file+0xd/0x10 [ 9.067000] [<c02849e0>] device_remove_file+0x23/0x2e [ 9.067000] [<c02850b2>] device_del+0x188/0x1e6 [ 9.067000] [<c028511b>] device_unregister+0xb/0x15 [ 9.067000] [<c0285318>] device_destroy+0x9c/0xa9 [ 9.067000] [<c0261431>] vcs_remove_sysfs+0x1c/0x3b [ 9.067000] [<c0267a08>] con_close+0x5e/0x6b [ 9.067000] [<c02598f2>] release_dev+0x4c4/0x6e5 [ 9.067000] [<c0259faa>] tty_release+0x12/0x1c [ 9.067000] [<c0174872>] __fput+0x177/0x1a0 [ 9.067000] [<c01746f5>] fput+0x3b/0x41 [ 9.068000] [<c0172ee1>] filp_close+0x36/0x65 [ 9.068000] [<c0172f73>] sys_close+0x63/0xa4 [ 9.068000] [<c0102a96>] 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 <frederik.deweerdt@gmail.com> 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; -