On Thu, 12 Jul 2012, Mike Galbraith wrote:
> crash> struct rt_mutex 0xffff8801770601c8
> struct rt_mutex {
> wait_lock = {
> raw_lock = {
> slock = 7966
> }
> },
> wait_list = {
> node_list = {
> next = 0xffff880175eedbe0,
> prev = 0xffff880175eedbe0
> },
> rawlock = 0xffff880175eedbd8,
Urgh. Here is something completely wrong. That should point to
wait_lock, i.e. the rt_mutex itself, but that points into lala land.
> spinlock = 0x0
> },
> owner = 0x1,
> save_state = 0,
> file = 0x0,
> name = 0xffffffff81781b9b "&(&device->io_lock)->lock",
> line = 0,
> magic = 0x0
> }
> crash> struct list_head 0xffff880175eedbe0
> struct list_head {
> next = 0x6b6b6b6b6b6b6b6b,
> prev = 0x6b6b6b6b6b6b6b6b
> }
That's POISON_FREE. How the heck can this happen ?
> Reproducer2: dbench -t 30 8
>
> [ 692.857164]
> [ 692.857165] ============================================
> [ 692.863963] [ BUG: circular locking deadlock detected! ]
> [ 692.869264] Not tainted
> [ 692.871708] --------------------------------------------
> [ 692.877008] btrfs-delayed-m/1404 is deadlocking current task dbench/7937
> [ 692.877009]
> [ 692.885183]
> [ 692.885184] 1) dbench/7937 is trying to acquire this lock:
> [ 692.892149] [ffff88014d6aea80] {&(&eb->lock)->lock}
> [ 692.897102] .. ->owner: ffff880175808501
> [ 692.901018] .. held by: btrfs-delayed-m: 1404 [ffff880175808500, 120]
> [ 692.907657]
> [ 692.907657] 2) btrfs-delayed-m/1404 is blocked on this lock:
> [ 692.914797] [ffff88014bf58d60] {&(&eb->lock)->lock}
> [ 692.919751] .. ->owner: ffff880175186101
> [ 692.923672] .. held by: dbench: 7937 [ffff880175186100, 120]
> [ 692.930309]
> [ 692.930309] btrfs-delayed-m/1404's [blocked] stackdump:
Hrmm. Both locks are rw_locks and we prevent multiple readers for the
known reasons in RT. No idea how to deal with that one :(
Thanks,
tglx
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