Re: Issues with possible recursive locking

[Srinivasa Ds <srinivasa@in.ibm.com>]

Mark Fasheh wrote:
> On Wed, Oct 18, 2006 at 09:37:58AM +0530, Srinivasa Ds wrote:
>   
>> When I was removing dlm module,I hit in to below error.
>>     
> This patch should take care of that particular warning, please let me know
> if it doesn't. I'll carry it in ocfs2.git shortly.
>   
Thanks Mark,It worked fine for me.
> Hmm, I get other warnings from configfs starting and stopping the ocfs2
> cluster stack, so I bet we've got some more mutex_lock() calls in there to
> change to mutex_lock_nested():
>
> [ INFO: possible recursive locking detected ]
> 2.6.19-rc2 #1
> ---------------------------------------------
> o2cb_ctl/2457 is trying to acquire lock:
>  (&inode->i_mutex){--..}, at: [<c02ff984>] mutex_lock+0x21/0x24
>
> but task is already holding lock:
>  (&inode->i_mutex){--..}, at: [<c02ff984>] mutex_lock+0x21/0x24
>
> other info that might help us debug this:
> 2 locks held by o2cb_ctl/2457:
>  #0:  (&inode->i_mutex/1){--..}, at: [<c0177194>] lookup_create+0x1d/0x73
>  #1:  (&inode->i_mutex){--..}, at: [<c02ff984>] mutex_lock+0x21/0x24
>
> stack backtrace:
>  [<c0104d0a>] dump_trace+0x64/0x1c2
>  [<c0104e7a>] show_trace_log_lvl+0x12/0x25
>  [<c01053c6>] show_trace+0xd/0x10
>  [<c01054dc>] dump_stack+0x19/0x1b
>  [<c013c7bb>] __lock_acquire+0x6c6/0x8e3
>  [<c013cf1b>] lock_acquire+0x4b/0x6c
>  [<c02ff81d>] __mutex_lock_slowpath+0xb0/0x1f6
>  [<c02ff984>] mutex_lock+0x21/0x24
>  [<f8aa2800>] configfs_add_file+0x36/0x60 [configfs]
>  [<f8aa285f>] configfs_create_file+0x35/0x38 [configfs]
>  [<f8aa3260>] configfs_attach_item+0x13d/0x180 [configfs]
>  [<f8aa32b7>] configfs_attach_group+0x14/0x154 [configfs]
>  [<f8aa3377>] configfs_attach_group+0xd4/0x154 [configfs]
>  [<f8aa3d8b>] configfs_mkdir+0x1b2/0x287 [configfs]
>  [<c017666a>] vfs_mkdir+0xca/0x131
>  [<c0178c8d>] sys_mkdirat+0x88/0xbb
>  [<c0178cd0>] sys_mkdir+0x10/0x12
>  [<c0103e2b>] syscall_call+0x7/0xb
> 	--Mark
>
>
> configfs: mutex_lock_nested() fix
>
> configfs_unregister_subsystem() nests a pair of inode i_mutex acquisitions,
> and thus needs annotation via mutex_lock_nested().
>
> Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
>
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 8a3b6a1..452cfd1 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -1176,8 +1176,9 @@ void configfs_unregister_subsystem(struc
>  		return;
>  	}
>  
> -	mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
> -	mutex_lock(&dentry->d_inode->i_mutex);
> +	mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
> +			  I_MUTEX_PARENT);
> +	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
>  	if (configfs_detach_prep(dentry)) {
>  		printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
>  	}
> -
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