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Subject2.6.17-rc6-mm1/pktcdvd - BUG: possible circular locking
Hello,

This BUG happened while pktcdvd service was starting.
Basically, the 2 following commands were issued:
- modprobe ptkcdvd
- pktsetup dvd /dev/dvd


cdrom: This disc doesn't have any tracks I recognize!
pktcdvd: writer pktcdvd0 mapped to hdc

=====================================================
[ BUG: possible circular locking deadlock detected! ]
-----------------------------------------------------
vol_id/2298 is trying to acquire lock:
(&ctl_mutex){....}, at: [<c027fa01>] mutex_lock+0x21/0x24

but task is already holding lock:
(&bdev->bd_mutex){....}, at: [<c0155009>] do_open+0x68/0x38b

which lock already depends on the new lock,
which could lead to circular deadlocks!

the existing dependency chain (in reverse order) is:

-> #1 (&bdev->bd_mutex){....}:
[<c01294c1>] lock_acquire+0x43/0x5c
[<c027fab7>] mutex_lock_nested+0xb3/0x1db
[<c0155009>] do_open+0x68/0x38b
[<c015539a>] blkdev_get+0x6e/0x79
[<e0ebf2aa>] pkt_ctl_ioctl+0x20f/0x586 [pktcdvd]
[<c015cea0>] do_ioctl+0x3c/0x4f
[<c015d0b6>] vfs_ioctl+0x203/0x21a
[<c015d0f9>] sys_ioctl+0x2c/0x47
[<c0280985>] sysenter_past_esp+0x56/0x79

-> #0 (&ctl_mutex){....}:
[<c01294c1>] lock_acquire+0x43/0x5c
[<c027f8b8>] __mutex_lock_slowpath+0x9b/0x1c3
[<c027fa01>] mutex_lock+0x21/0x24
[<e0ebffd7>] pkt_open+0x1e/0xbef [pktcdvd]
[<c015503b>] do_open+0x9a/0x38b
[<c01554b3>] blkdev_open+0x1f/0x48
[<c014d229>] __dentry_open+0xb8/0x186
[<c014d365>] nameidata_to_filp+0x1c/0x2e
[<c014d3a5>] do_filp_open+0x2e/0x35
[<c014e24a>] do_sys_open+0x40/0xbb
[<c014e2f1>] sys_open+0x16/0x18
[<c0280985>] sysenter_past_esp+0x56/0x79

other info that might help us debug this:

1 lock held by vol_id/2298:
#0: (&bdev->bd_mutex){....}, at: [<c0155009>] do_open+0x68/0x38b

stack backtrace:
[<c0104836>] show_trace+0xd/0x10
[<c0104852>] dump_stack+0x19/0x1b
[<c0128c32>] print_circular_bug_tail+0x59/0x64
[<c0129358>] __lock_acquire+0x5a9/0x6cf
[<c01294c1>] lock_acquire+0x43/0x5c
[<c027f8b8>] __mutex_lock_slowpath+0x9b/0x1c3
[<c027fa01>] mutex_lock+0x21/0x24
[<e0ebffd7>] pkt_open+0x1e/0xbef [pktcdvd]
[<c015503b>] do_open+0x9a/0x38b
[<c01554b3>] blkdev_open+0x1f/0x48
[<c014d229>] __dentry_open+0xb8/0x186
[<c014d365>] nameidata_to_filp+0x1c/0x2e
[<c014d3a5>] do_filp_open+0x2e/0x35
[<c014e24a>] do_sys_open+0x40/0xbb
[<c014e2f1>] sys_open+0x16/0x18
[<c0280985>] sysenter_past_esp+0x56/0x79
-
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