With radeon KMS, after using a program accessing the framebuffer,
I started X and got this:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.34-rc6 #117
-------------------------------------------------------
X/1846 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff8108d36f>] might_fault+0x57/0xa4
but task is already holding lock:
(&dev->mode_config.mutex){+.+.+.}, at: [<ffffffff8125f258>] drm_mode_getresources+0x33/0x54d
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&dev->mode_config.mutex){+.+.+.}:
[<ffffffff8105d185>] __lock_acquire+0x1408/0x1747
[<ffffffff8105d51e>] lock_acquire+0x5a/0x71
[<ffffffff8143284a>] mutex_lock_nested+0x58/0x2b1
[<ffffffff8124e1d8>] drm_fb_helper_set_par+0x9c/0xf2
[<ffffffff811de45f>] fb_set_var+0x1de/0x2d9
[<ffffffff811de694>] do_fb_ioctl+0x13a/0x46e
[<ffffffff811dede2>] fb_ioctl+0x21/0x23
[<ffffffff810b3c80>] vfs_ioctl+0x2a/0x9e
[<ffffffff810b4235>] do_vfs_ioctl+0x4b7/0x4f4
[<ffffffff810b42b4>] sys_ioctl+0x42/0x65
[<ffffffff81001feb>] system_call_fastpath+0x16/0x1b
-> #1 (&fb_info->lock){+.+.+.}:
[<ffffffff8105d185>] __lock_acquire+0x1408/0x1747
[<ffffffff8105d51e>] lock_acquire+0x5a/0x71
[<ffffffff8143284a>] mutex_lock_nested+0x58/0x2b1
[<ffffffff811dd60a>] fb_release+0x1c/0x54
[<ffffffff810a8585>] __fput+0x120/0x1e3
[<ffffffff810a8660>] fput+0x18/0x1a
[<ffffffff81093287>] remove_vma+0x51/0x76
[<ffffffff81094245>] do_munmap+0x30a/0x32e
[<ffffffff810942a4>] sys_munmap+0x3b/0x54
[<ffffffff81001feb>] system_call_fastpath+0x16/0x1b
-> #0 (&mm->mmap_sem){++++++}:
[<ffffffff8105ceaa>] __lock_acquire+0x112d/0x1747
[<ffffffff8105d51e>] lock_acquire+0x5a/0x71
[<ffffffff8108d39c>] might_fault+0x84/0xa4
[<ffffffff8125f4a5>] drm_mode_getresources+0x280/0x54d
[<ffffffff8125519f>] drm_ioctl+0x255/0x34b
[<ffffffff810b3c80>] vfs_ioctl+0x2a/0x9e
[<ffffffff810b4235>] do_vfs_ioctl+0x4b7/0x4f4
[<ffffffff810b42b4>] sys_ioctl+0x42/0x65
[<ffffffff81001feb>] system_call_fastpath+0x16/0x1b
other info that might help us debug this:
1 lock held by X/1846:
#0: (&dev->mode_config.mutex){+.+.+.}, at: [<ffffffff8125f258>] drm_mode_getresources+0x33/0x54d
stack backtrace:
Pid: 1846, comm: X Not tainted 2.6.34-rc6 #117
Call Trace:
[<ffffffff8105b82f>] print_circular_bug+0xb3/0xc2
[<ffffffff8105ceaa>] __lock_acquire+0x112d/0x1747
[<ffffffff8105aef4>] ? mark_held_locks+0x4d/0x6b
[<ffffffff81432a88>] ? mutex_lock_nested+0x296/0x2b1
[<ffffffff8105d51e>] lock_acquire+0x5a/0x71
[<ffffffff8108d36f>] ? might_fault+0x57/0xa4
[<ffffffff8108d39c>] might_fault+0x84/0xa4
[<ffffffff8108d36f>] ? might_fault+0x57/0xa4
[<ffffffff8125f4a5>] drm_mode_getresources+0x280/0x54d
[<ffffffff8125519f>] drm_ioctl+0x255/0x34b
[<ffffffff8125f225>] ? drm_mode_getresources+0x0/0x54d
[<ffffffff8104f629>] ? up_read+0x1e/0x35
[<ffffffff810b3c80>] vfs_ioctl+0x2a/0x9e
[<ffffffff810b4235>] do_vfs_ioctl+0x4b7/0x4f4
[<ffffffff8100201c>] ? sysret_check+0x27/0x62
[<ffffffff810b42b4>] sys_ioctl+0x42/0x65
[<ffffffff81001feb>] system_call_fastpath+0x16/0x1b
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