Messages in this thread Patch in this message | | | Date | Tue, 20 May 2008 18:33:23 +0200 | From | Louis Rilling <> | Subject | [RFC][PATCH 3/3] configfs: Silence lockdep when destroying default groups |
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When destroying a config_group having default groups, lockdep raises a warning because multiple locks of class I_MUTEX_NORMAL are taken in configfs_detach_prep() (the first one being in vfs_rmdir()). However this recursive locking is another instance of I_MUTEX_PARENT -> I_MUTEX_CHILD dependency, which was already checked correct when creating the config_group, and which lockdep cannot handle cleanly because of the variable depth.
This patch silences lockdep when destroying default groups by simply hiding the inode mutex locks from lockdep in configfs_detach_prep(), configfs_detach_rollback(), and detach_groups().
============================================= [ INFO: possible recursive locking detected ] 2.6.26-rc3 #5 --------------------------------------------- rmdir/1499 is trying to acquire lock: (&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff802d2529>] configfs_detach_prep+0x54/0x89
but task is already holding lock: (&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff80296513>] vfs_rmdir+0x49/0xac
other info that might help us debug this: 2 locks held by rmdir/1499: #0: (&sb->s_type->i_mutex_key#3/1){--..}, at: [<ffffffff80298138>] do_rmdir+0x82/0x108 #1: (&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff80296513>] vfs_rmdir+0x49/0xac
stack backtrace: Pid: 1499, comm: rmdir Not tainted 2.6.26-rc3 #5
Call Trace: [<ffffffff8024afe9>] __lock_acquire+0x8d2/0xc78 [<ffffffff80266399>] filemap_fault+0x1cf/0x332 [<ffffffff802d2529>] configfs_detach_prep+0x54/0x89 [<ffffffff8024b762>] lock_acquire+0x51/0x6c [<ffffffff802d2529>] configfs_detach_prep+0x54/0x89 [<ffffffff80248331>] debug_mutex_lock_common+0x16/0x23 [<ffffffff805d6244>] mutex_lock_nested+0xcd/0x23b [<ffffffff802d2529>] configfs_detach_prep+0x54/0x89 [<ffffffff802d3656>] configfs_rmdir+0xb8/0x1c3 [<ffffffff80296535>] vfs_rmdir+0x6b/0xac [<ffffffff8029816d>] do_rmdir+0xb7/0x108 [<ffffffff8024a2a2>] trace_hardirqs_on+0xef/0x113 [<ffffffff805d7364>] trace_hardirqs_on_thunk+0x35/0x3a [<ffffffff8020b0cb>] system_call_after_swapgs+0x7b/0x80
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> --- fs/configfs/dir.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
Index: b/fs/configfs/dir.c =================================================================== --- a/fs/configfs/dir.c 2008-05-20 18:19:41.000000000 +0200 +++ b/fs/configfs/dir.c 2008-05-20 18:19:45.000000000 +0200 @@ -352,7 +352,12 @@ static int configfs_detach_prep(struct d if (sd->s_type & CONFIGFS_NOT_PINNED) continue; if (sd->s_type & CONFIGFS_USET_DEFAULT) { + /* Hide this mutex from lockdep for the same reasons as in + * populate_groups() + */ + lockdep_off(); mutex_lock(&sd->s_dentry->d_inode->i_mutex); + lockdep_on(); /* Mark that we've taken i_mutex */ sd->s_type |= CONFIGFS_USET_DROPPING; @@ -388,7 +393,12 @@ static void configfs_detach_rollback(str if (sd->s_type & CONFIGFS_USET_DROPPING) { sd->s_type &= ~CONFIGFS_USET_DROPPING; + /* This mutex was hidden from lockdep in + * configfs_detach_prep() + */ + lockdep_off(); mutex_unlock(&sd->s_dentry->d_inode->i_mutex); + lockdep_on(); } } } @@ -475,8 +485,14 @@ static void detach_groups(struct config_ * has taken our i_mutex for us. Drop it. * From mkdir/register cleanup, there is no sem held. */ - if (sd->s_type & CONFIGFS_USET_DROPPING) + if (sd->s_type & CONFIGFS_USET_DROPPING) { + /* This mutex was hidden from lockdep in + * configfs_detach_prep() + */ + lockdep_off(); mutex_unlock(&child->d_inode->i_mutex); + lockdep_on(); + } d_delete(child); dput(child); -- Dr Louis Rilling Kerlabs Skype: louis.rilling Batiment Germanium Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes http://www.kerlabs.com/ 35700 Rennes
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