Re: [BUG?] possible recursive locking detected

[Nick Piggin]

Andrew Morton wrote:
> On Wed, 26 Jul 2006 18:05:21 +0200
> Rolf Eike Beer <eike-kernel@xxxxxxxxx> wrote:
>
>
> > Hi,
> >
> > I did some memory stress test (allocating and mlock()ing a huge number of 
> > pages) from userspace. At the very beginning of that I got that error long 
> > before the system got unresponsible and the oom killer dropped in.
> >
> > Eike
> >
> > =============================================
> > [ INFO: possible recursive locking detected ]
> > kded/5304 is trying to acquire lock:
> > (&inode->i_mutex){--..}, at: [<c11f476e>] mutex_lock+0x21/0x24
> >
> > but task is already holding lock:
> > (&inode->i_mutex){--..}, at: [<c11f476e>] mutex_lock+0x21/0x24
> >
> > other info that might help us debug this:
> > 3 locks held by kded/5304:
> > #0:  (&inode->i_mutex){--..}, at: [<c11f476e>] mutex_lock+0x21/0x24
> > #1:  (shrinker_rwsem){----}, at: [<c1046312>] shrink_slab+0x25/0x136
> > #2:  (&type->s_umount_key#14){----}, at: [<c106be2e>] prune_dcache+0xf6/0x144
> >
> > stack backtrace:
> > [<c1003aa9>] show_trace_log_lvl+0x54/0xfd
> > [<c1004915>] show_trace+0xd/0x10
> > [<c100492f>] dump_stack+0x17/0x1c
> > [<c102e0e1>] __lock_acquire+0x753/0x99c
> > [<c102e5ac>] lock_acquire+0x4a/0x6a
> > [<c11f4609>] __mutex_lock_slowpath+0xb0/0x1f4
> > [<c11f476e>] mutex_lock+0x21/0x24
> > [<f0854fc4>] ntfs_put_inode+0x3b/0x74 [ntfs]
> > [<c106cf3f>] iput+0x33/0x6a
> > [<c106b707>] dentry_iput+0x5b/0x73
> > [<c106bd15>] prune_one_dentry+0x56/0x79
> > [<c106be42>] prune_dcache+0x10a/0x144
> > [<c106be95>] shrink_dcache_memory+0x19/0x31
> > [<c10463bd>] shrink_slab+0xd0/0x136
> > [<c1047494>] try_to_free_pages+0x129/0x1d5
> > [<c1043d91>] __alloc_pages+0x18e/0x284
> > [<c104044b>] read_cache_page+0x59/0x131
> > [<c109e96f>] ext2_get_page+0x1c/0x1ff
> > [<c109ebc4>] ext2_find_entry+0x72/0x139
> > [<c109ec99>] ext2_inode_by_name+0xe/0x2e
> > [<c10a1cad>] ext2_lookup+0x1f/0x65
> > [<c1064661>] do_lookup+0xa0/0x134
> > [<c1064e9a>] __link_path_walk+0x7a5/0xbe4
> > [<c1065329>] link_path_walk+0x50/0xca
> > [<c106586d>] do_path_lookup+0x212/0x25a
> > [<c1065da9>] __user_walk_fd+0x2d/0x41
> > [<c10600bd>] vfs_stat_fd+0x19/0x40
> > [<c10600f5>] vfs_stat+0x11/0x13
> > [<c1060826>] sys_stat64+0x14/0x2a
> > [<c1002845>] sysenter_past_esp+0x56/0x8d
>
>
> We hold the ext2 directory mutex, and ntfs_put_inode is trying to take an
> ntfs i_mutex.  Not a deadlock as such, but it could become one in ntfs if
> ntfs ever does a __GFP_WAIT allocation inside i_mutex, which it surely
> does.

Though it should be using GFP_NOFS, right? So the dcache shrinker would
not reenter the fs in that case.

I'm surprised ext2 is allocating with __GFP_FS set, though. Would that
cause any problem?

--
SUSE Labs, Novell Inc.
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