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    Subject[PATCH 18/28] sysfs: suppress lockdep warnings
    Date
    From: Frederik Deweerdt <deweerdt@free.fr>

    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.

    Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com>
    Cc: Oliver Neukum <oliver@neukum.org>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    fs/sysfs/inode.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
    index 1a81ebc..dbd820f 100644
    --- a/fs/sysfs/inode.c
    +++ b/fs/sysfs/inode.c
    @@ -215,7 +215,7 @@ static inline void orphan_all_buffers(struct inode *node)
    struct sysfs_buffer_collection *set = node->i_private;
    struct sysfs_buffer *buf;

    - mutex_lock(&node->i_mutex);
    + mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
    if (node->i_private) {
    list_for_each_entry(buf, &set->associates, associates) {
    down(&buf->sem);
    @@ -272,7 +272,7 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name)
    return -ENOENT;

    parent_sd = dir->d_fsdata;
    - mutex_lock(&dir->d_inode->i_mutex);
    + mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
    list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
    if (!sd->s_element)
    continue;
    --
    1.4.4.4
    -
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