Re: starting mc triggers lockdep

On Sat, 2006-07-08 at 13:00 +1000, Herbert Xu wrote:

Arjan van de Ven [off-list ref] wrote:

quoted

i_mutex is taken within rtln_mutex like this:
      [<ffffffff8030f4a0>] create_dir+0x2c/0x1e2
      [<ffffffff8030fa5b>] sysfs_create_dir+0x59/0x78
      [<ffffffff8034d2e2>] kobject_add+0x114/0x1d8
      [<ffffffff803bb1e7>] class_device_add+0xb5/0x49d
      [<ffffffff804300b1>] netdev_register_sysfs+0x98/0xa2
      [<ffffffff80426f58>] register_netdevice+0x28c/0x376
      [<ffffffff8042709c>] register_netdev+0x5a/0x69
creating the AB dependency

This is a sysfs inode.

quoted

now for the third part, which involves the nfs client:
stat on an nfs file, which ends up taken the i_mutex of a directory in
the path (obvious), and then does 
      [<ffffffff8022800b>] tcp_sendmsg+0x1e/0xb1a
      [<ffffffff80248f4b>] inet_sendmsg+0x45/0x53
      [<ffffffff80259d25>] sock_sendmsg+0x110/0x130
      [<ffffffff8041f462>] kernel_sendmsg+0x3c/0x52
      [<ffffffff885399e9>] xs_tcp_send_request+0x117/0x320 [sunrpc]
      [<ffffffff885388d5>] xprt_transmit+0x105/0x21e [sunrpc]
      [<ffffffff8853771e>] call_transmit+0x1f4/0x239 [sunrpc]
      [<ffffffff8853c06e>] __rpc_execute+0x9b/0x1e6 [sunrpc]
      [<ffffffff8853c1de>] rpc_execute+0x1a/0x1d [sunrpc]
      [<ffffffff885364ad>] rpc_call_sync+0x87/0xb9 [sunrpc]
      [<ffffffff885a2587>] nfs3_rpc_wrapper+0x2e/0x74 [nfs]
      [<ffffffff885a2a14>] nfs3_proc_lookup+0xe0/0x163 [nfs]
where tcp_sendmsg calls lock_sock. So this is the BC dependency.

This is an nfs inode.

Did I miss something?

is it not possible to nfs export /sys, and then mount it over loopback?