Re: [Bug #12419] possible circular locking dependency on i915 dma

[Wang Chen <wangchen@cn.fujitsu.com>]

Rafael J. Wysocki said the following on 2009-2-24 5:48:
> This message has been generated automatically as a part of a report
> of recent regressions.
> 
> The following bug entry is on the current list of known regressions
> from 2.6.28.  Please verify if it still should be listed and let me know
> (either way).
> 
> 
> Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=12419
> Subject		: possible circular locking dependency on i915 dma
> Submitter	: Wang Chen <wangchen@cn.fujitsu.com>
> Date		: 2009-01-08 14:11 (47 days old)
> First-Bad-Commit: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=546b0974c39657017407c86fe79811100b60700d
> References	: http://marc.info/?l=linux-kernel&m=123142399720125&w=4
> 

not changed.

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.29-rc6-default #165
-------------------------------------------------------
X/3940 is trying to acquire lock:
 (&mm->mmap_sem){----}, at: [<c0168e97>] might_fault+0x42/0x7e

but task is already holding lock:
 (&dev->struct_mutex){--..}, at: [<eeb76fed>] i915_cmdbuffer+0xf4/0x411 [i915]

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&dev->struct_mutex){--..}:
       [<c013791a>] validate_chain+0x8be/0xbb5
       [<c0138280>] __lock_acquire+0x66f/0x6f9
       [<c0138365>] lock_acquire+0x5b/0x77
       [<c02e56fe>] mutex_lock_nested+0xdb/0x244
       [<eeb5b03e>] drm_vm_open+0x25/0x37 [drm]
       [<c011a8b3>] dup_mm+0x247/0x2f2
       [<c011b312>] copy_process+0x98c/0xfeb
       [<c011bac7>] do_fork+0x120/0x29c
       [<c01016be>] sys_clone+0x25/0x2a
       [<c0102cdd>] sysenter_do_call+0x12/0x31
       [<ffffffff>] 0xffffffff

-> #1 (&mm->mmap_sem/1){--..}:
       [<c013791a>] validate_chain+0x8be/0xbb5
       [<c0138280>] __lock_acquire+0x66f/0x6f9
       [<c0138365>] lock_acquire+0x5b/0x77
       [<c012e6f6>] down_write_nested+0x32/0x4f
       [<c011a711>] dup_mm+0xa5/0x2f2
       [<c011b312>] copy_process+0x98c/0xfeb
       [<c011bac7>] do_fork+0x120/0x29c
       [<c01016be>] sys_clone+0x25/0x2a
       [<c0102cdd>] sysenter_do_call+0x12/0x31
       [<ffffffff>] 0xffffffff

-> #0 (&mm->mmap_sem){----}:
       [<c0137625>] validate_chain+0x5c9/0xbb5
       [<c0138280>] __lock_acquire+0x66f/0x6f9
       [<c0138365>] lock_acquire+0x5b/0x77
       [<c0168eb4>] might_fault+0x5f/0x7e
       [<eeb76d0a>] i915_emit_box+0x1d/0x20c [i915]
       [<eeb7705e>] i915_cmdbuffer+0x165/0x411 [i915]
       [<eeb5685b>] drm_ioctl+0x1a6/0x21b [drm]
       [<c0182b29>] vfs_ioctl+0x3d/0x50
       [<c0183029>] do_vfs_ioctl+0x41b/0x483
       [<c01830d1>] sys_ioctl+0x40/0x5a
       [<c0102cdd>] sysenter_do_call+0x12/0x31
       [<ffffffff>] 0xffffffff