possible circular locking dependency detected

[Marko Macek <Marko.Macek@gmx.net>]

Hello!

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.21.1-cfs-v11 #4
-------------------------------------------------------
tvtime/6360 is trying to acquire lock:
(&mm->mmap_sem){----}, at: [<f8a6a50a>] 
videobuf_dma_init_user+0xb6/0x14e [video_buf]

but task is already holding lock:
(&q->lock#2){--..}, at: [<f8a6ac43>] videobuf_qbuf+0x10/0x288 [video_buf]

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&q->lock#2){--..}:
      [<c01437eb>] __lock_acquire+0x9de/0xb58
      [<f8a695fe>] videobuf_mmap_mapper+0x12/0x1ff [video_buf]
      [<c0143d19>] lock_acquire+0x56/0x6e
      [<f8a695fe>] videobuf_mmap_mapper+0x12/0x1ff [video_buf]
      [<c032579a>] __mutex_lock_slowpath+0xe3/0x23b
      [<f8a695fe>] videobuf_mmap_mapper+0x12/0x1ff [video_buf]
      [<f8a695fe>] videobuf_mmap_mapper+0x12/0x1ff [video_buf]
      [<c0173559>] kmem_cache_zalloc+0x69/0x97
      [<c0142a07>] trace_hardirqs_on+0x11e/0x141
      [<c0168eea>] do_mmap_pgoff+0x43e/0x714
      [<c0108adb>] sys_mmap2+0x9d/0xb7
      [<c0104d9e>] sysenter_past_esp+0x5f/0x99
      [<ffffffff>] 0xffffffff

-> #0 (&mm->mmap_sem){----}:
      [<c014170f>] print_circular_bug_entry+0x40/0x46
      [<c01436d7>] __lock_acquire+0x8ca/0xb58
      [<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
      [<c0143d19>] lock_acquire+0x56/0x6e
      [<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
      [<c013d082>] down_read+0x3d/0x4e
      [<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
      [<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
      [<f8a69ae7>] videobuf_waiton+0xdf/0xe9 [video_buf]
      [<f8a6a836>] videobuf_iolock+0x7f/0xdf [video_buf]
      [<f8a7fdb2>] buffer_prepare+0x174/0x1d8 [saa7134]
      [<c03258ea>] __mutex_lock_slowpath+0x233/0x23b
      [<f8a6ac43>] videobuf_qbuf+0x10/0x288 [video_buf]
      [<f8a6ae23>] videobuf_qbuf+0x1f0/0x288 [video_buf]
      [<c0159626>] find_get_page+0x40/0x45
      [<f8a8144d>] video_do_ioctl+0xd6f/0xec7 [saa7134]
      [<c0326a8a>] _spin_unlock+0x14/0x1c
      [<f8a0e946>] video_usercopy+0x172/0x237 [videodev]
      [<c0328621>] do_page_fault+0x202/0x5df
      [<f8a7ef74>] video_ioctl+0x18/0x1c [saa7134]
      [<f8a806de>] video_do_ioctl+0x0/0xec7 [saa7134]
      [<c0180ca0>] do_ioctl+0x4c/0x62
      [<c0180efa>] vfs_ioctl+0x244/0x256
      [<c0180f58>] sys_ioctl+0x4c/0x64
      [<c0104d9e>] sysenter_past_esp+0x5f/0x99
      [<ffffffff>] 0xffffffff

other info that might help us debug this:

1 lock held by tvtime/6360:
#0:  (&q->lock#2){--..}, at: [<f8a6ac43>] videobuf_qbuf+0x10/0x288 
[video_buf]

stack backtrace:
[<c0141fa7>] print_circular_bug_tail+0x5f/0x67
[<c014170f>] print_circular_bug_entry+0x40/0x46
[<c01436d7>] __lock_acquire+0x8ca/0xb58
[<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
[<c0143d19>] lock_acquire+0x56/0x6e
[<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
[<c013d082>] down_read+0x3d/0x4e
[<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
[<f8a6a50a>] videobuf_dma_init_user+0xb6/0x14e [video_buf]
[<f8a69ae7>] videobuf_waiton+0xdf/0xe9 [video_buf]
[<f8a6a836>] videobuf_iolock+0x7f/0xdf [video_buf]
[<f8a7fdb2>] buffer_prepare+0x174/0x1d8 [saa7134]
[<c03258ea>] __mutex_lock_slowpath+0x233/0x23b
[<f8a6ac43>] videobuf_qbuf+0x10/0x288 [video_buf]
[<f8a6ae23>] videobuf_qbuf+0x1f0/0x288 [video_buf]
[<c0159626>] find_get_page+0x40/0x45
[<f8a8144d>] video_do_ioctl+0xd6f/0xec7 [saa7134]
[<c0326a8a>] _spin_unlock+0x14/0x1c
[<f8a0e946>] video_usercopy+0x172/0x237 [videodev]
[<c0328621>] do_page_fault+0x202/0x5df
[<f8a7ef74>] video_ioctl+0x18/0x1c [saa7134]
[<f8a806de>] video_do_ioctl+0x0/0xec7 [saa7134]
[<c0180ca0>] do_ioctl+0x4c/0x62
[<c0180efa>] vfs_ioctl+0x244/0x256
[<c0180f58>] sys_ioctl+0x4c/0x64
[<c0104d9e>] sysenter_past_esp+0x5f/0x99
=======================


The TV card is saa7134.
Machine is AMD Athlon 64 X2. Fedora Core 6.

I get a lockup while watching TV about every month or two. Machine 
responds to ping, but nothing else.

Mark
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