BUG: spinlock recursion on CPU

== About ==
* Kernel version: 2.6.38-rc1
* [https://bugzilla.kernel.org/show_bug.cgi?id=27022 Bug 27022]
* Reported by: Santosh Shilimkar (January 10, 2011) (linux-kernel@vger.kernel.org)
* Reported by: Maciej Rutecki (January 18, 2011) (bugzilla)
* Reported fixed by: Nick Piggin (January 19, 2011)
* Closed by: Florian Mickler (March 27, 2011)


== Symptoms ==
* Rootfs mounted on NFS
<pre>
VFS: Mounted root (nfs filesystem) on device 0:13.
Freeing init memory: 296K
BUG: spinlock recursion on CPU#0, init/1
 lock: ef5a1e0c, .magic: dead4ead, .owner: init/1, .owner_cpu: 0
[<c0063290>] (unwind_backtrace+0x0/0xe4) from [<c024ce90>]
(do_raw_spin_lock+0x48/0x158)
[<c024ce90>] (do_raw_spin_lock+0x48/0x158) from [<c012f4e0>]
(nameidata_dentry_drop_rcu+0x84/0x17c)
[<c012f4e0>] (nameidata_dentry_drop_rcu+0x84/0x17c) from [<c012f608>]
(d_revalidate+0x30/0x58)
[<c012f608>] (d_revalidate+0x30/0x58) from [<c0132120>]
(link_path_walk+0xb44/0xb64)
[<c0132120>] (link_path_walk+0xb44/0xb64) from [<c0132338>]
(do_path_lookup+0x44/0xcc)
[<c0132338>] (do_path_lookup+0x44/0xcc) from [<c0132f08>]
(do_filp_open+0xc8/0x56c)
[<c0132f08>] (do_filp_open+0xc8/0x56c) from [<c0124828>]
(do_sys_open+0x58/0xe4)
[<c0124828>] (do_sys_open+0x58/0xe4) from [<c005c240>]
(ret_fast_syscall+0x0/0x3c)
BUG: spinlock lockup on CPU#0, init/1, ef5a1e0c
[<c0063290>] (unwind_backtrace+0x0/0xe4) from [<c024cf84>]
(do_raw_spin_lock+0x13c/0x158)
[<c024cf84>] (do_raw_spin_lock+0x13c/0x158) from [<c012f4e0>]
(nameidata_dentry_drop_rcu+0x84/0x17c)
[<c012f4e0>] (nameidata_dentry_drop_rcu+0x84/0x17c) from [<c012f608>]
(d_revalidate+0x30/0x58)
[<c012f608>] (d_revalidate+0x30/0x58) from [<c0132120>]
(link_path_walk+0xb44/0xb64)
[<c0132120>] (link_path_walk+0xb44/0xb64) from [<c0132338>]
(do_path_lookup+0x44/0xcc)
[<c0132338>] (do_path_lookup+0x44/0xcc) from [<c0132f08>]
(do_filp_open+0xc8/0x56c)
[<c0132f08>] (do_filp_open+0xc8/0x56c) from [<c0124828>]
(do_sys_open+0x58/0xe4)
[<c0124828>] (do_sys_open+0x58/0xe4) from [<c005c240>]
(ret_fast_syscall+0x0/0x3c)
BUG: spinlock lockup on CPU#1, kworker/u:2/499, c05d3c80
[<c0063290>] (unwind_backtrace+0x0/0xe4) from [<c024cf84>]
(do_raw_spin_lock+0x13c/0x158)
[<c024cf84>] (do_raw_spin_lock+0x13c/0x158) from [<c014afac>]
(exit_fs+0x2c/0x84)
[<c014afac>] (exit_fs+0x2c/0x84) from [<c0098274>] (do_exit+0x254/0x674)
[<c0098274>] (do_exit+0x254/0x674) from [<c00b0944>] (kthread+0x88/0x8c)
[<c00b0944>] (kthread+0x88/0x8c) from [<c005d490>]
(kernel_thread_exit+0x0/0x8)
</pre>