[Cluster-devel] Re: [PATCH 2/2] dlm: Add down/up_write_non_owner to keep lockdep happy

[Steven Whitehouse]

Hi,

On Thu, 2009-11-12 at 15:22 +0100, Ingo Molnar wrote:
> * Steven Whitehouse <swhiteho at redhat.com> wrote:
> 
> > I looked at possibly changing this to use completions, but
> > it seems that the usage here is not easily adapted to that.
> > This patch adds suitable annotation to the write side of
> > the ls_in_recovery semaphore so that we don't get nasty
> > messages from lockdep when mounting a gfs2 filesystem.
> 
> What do those 'nasty messages' say? If they expose some bug and this
> patch works around that bug by hiding it then NAK ...
> 
>         Ingo
> 
The nasty messages are moaning that the lock is being taken in one
thread and unlocked in another. I couldn't see any bugs in the code when
I looked at it. Below are the messages that I get - to reproduce just
mount a GFS2 filesystem with the dlm lock manager. It happens on every
mount,

Steve.

Nov 12 15:10:01 chywoon kernel:
=============================================
Nov 12 15:10:01 chywoon kernel: [ INFO: possible recursive locking
detected ]
Nov 12 15:10:01 chywoon kernel: 2.6.32-rc6 #46
Nov 12 15:10:01 chywoon kernel:
---------------------------------------------
Nov 12 15:10:01 chywoon kernel: mount.gfs2/2996 is trying to acquire
lock:
Nov 12 15:10:01 chywoon kernel: (&ls->ls_in_recovery){+++++.}, at:
[<ffffffffa01cf3b5>] dlm_lock+0x55/0x1b0 [dlm]
Nov 12 15:10:01 chywoon kernel:
Nov 12 15:10:01 chywoon kernel: but task is already holding lock:
Nov 12 15:10:01 chywoon kernel: (&ls->ls_in_recovery){+++++.}, at:
[<ffffffffa01d1e1c>] dlm_new_lockspace+0x96c/0xb80 [dlm]
Nov 12 15:10:01 chywoon kernel:
Nov 12 15:10:01 chywoon kernel: other info that might help us debug
this:
Nov 12 15:10:01 chywoon kernel: 2 locks held by mount.gfs2/2996:
Nov 12 15:10:01 chywoon kernel: #0:  (&type->s_umount_key#37/1){+.+.+.},
at: [<ffffffff81168698>] sget+0x258/0x4c0
Nov 12 15:10:01 chywoon kernel: #1:  (&ls->ls_in_recovery){+++++.}, at:
[<ffffffffa01d1e1c>] dlm_new_lockspace+0x96c/0xb80 [dlm]
Nov 12 15:10:01 chywoon kernel:
Nov 12 15:10:01 chywoon kernel: stack backtrace:
Nov 12 15:10:01 chywoon kernel: Pid: 2996, comm: mount.gfs2 Not tainted
2.6.32-rc6 #46
Nov 12 15:10:01 chywoon kernel: Call Trace:
Nov 12 15:10:01 chywoon kernel: [<ffffffff810c53e4>] validate_chain
+0xdd4/0x1170
Nov 12 15:10:01 chywoon kernel: [<ffffffff810c2a85>] ? mark_lock
+0x2e5/0x670
Nov 12 15:10:01 chywoon kernel: [<ffffffff810c5cb2>] __lock_acquire
+0x532/0xbc0
Nov 12 15:10:01 chywoon kernel: [<ffffffff81043e2c>] ?
native_sched_clock+0x2c/0x80
Nov 12 15:10:01 chywoon kernel: [<ffffffff810c6404>] lock_acquire
+0xc4/0x1b0
Nov 12 15:10:01 chywoon kernel: [<ffffffffa01cf3b5>] ? dlm_lock
+0x55/0x1b0 [dlm]
Nov 12 15:10:01 chywoon kernel: [<ffffffff81627317>] down_read+0x47/0x80
Nov 12 15:10:01 chywoon kernel: [<ffffffffa01cf3b5>] ? dlm_lock
+0x55/0x1b0 [dlm]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa01d0af6>] ?
dlm_find_lockspace_local+0x46/0x60 [dlm]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa01cf3b5>] dlm_lock+0x55/0x1b0
[dlm]
Nov 12 15:10:01 chywoon kernel: [<ffffffff81043df3>] ? sched_clock
+0x13/0x20
Nov 12 15:10:01 chywoon kernel: [<ffffffff810b4e1d>] ? sched_clock_cpu
+0xed/0x140
Nov 12 15:10:01 chywoon kernel: [<ffffffff810bf6fe>] ? put_lock_stats
+0xe/0x30
Nov 12 15:10:01 chywoon kernel: [<ffffffff810c10e1>] ?
lock_release_holdtime+0xb1/0x160
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0224a75>] gdlm_lock
+0xe5/0x120 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0224b70>] ? gdlm_ast+0x0/0xd0
[gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0224ab0>] ? gdlm_bast
+0x0/0x50 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa02081d3>] do_xmote+0xf3/0x2c0
[gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0208a21>] run_queue
+0x1a1/0x280 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0208cb4>] gfs2_glock_nq
+0x134/0x3b0 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa02099a9>] gfs2_glock_nq_num
+0x69/0x90 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0215a25>] init_locking
+0x45/0x190 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa0216440>] gfs2_get_sb
+0x8d0/0xc10 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffffa02099a1>] ? gfs2_glock_nq_num
+0x61/0x90 [gfs2]
Nov 12 15:10:01 chywoon kernel: [<ffffffff8115f9eb>] ? __alloc_percpu
+0xb/0x10
Nov 12 15:10:01 chywoon kernel: [<ffffffff81167838>] vfs_kern_mount
+0x58/0xf0
Nov 12 15:10:01 chywoon kernel: [<ffffffff8116793d>] do_kern_mount
+0x4d/0x130
Nov 12 15:10:01 chywoon kernel: [<ffffffff81629062>] ? lock_kernel
+0x42/0x109
Nov 12 15:10:01 chywoon kernel: [<ffffffff81186854>] do_mount
+0x2c4/0x820
Nov 12 15:10:01 chywoon kernel: [<ffffffff81186e3b>] sys_mount+0x8b/0xe0
Nov 12 15:10:01 chywoon kernel: [<ffffffff8103d0c2>]
system_call_fastpath+0x16/0x1b