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SubjectRe: INFO: possible circular locking dependency at cleanup_workqueue_thread
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> > =======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 2.6.30-rc5-00097-gd665355 #59
> > -------------------------------------------------------
> > pm-suspend/12129 is trying to acquire lock:
> > (events){+.+.+.}, at: [<ffffffff80259496>] cleanup_workqueue_thread+0x26/0xd0
> >
> > but task is already holding lock:
> > (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff80246e57>]
> > cpu_maps_update_begin+0x17/0x20
> >
> > which lock already depends on the new lock.
> >
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #5 (cpu_add_remove_lock){+.+.+.}:
> > [<ffffffff80271a64>] __lock_acquire+0xc64/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff8054e78c>] __mutex_lock_common+0x4c/0x3b0
> > [<ffffffff8054ebf6>] mutex_lock_nested+0x46/0x60
> > [<ffffffff80246e57>] cpu_maps_update_begin+0x17/0x20
> > [<ffffffff80259c33>] __create_workqueue_key+0xc3/0x250
> > [<ffffffff80287b20>] stop_machine_create+0x40/0xb0
> > [<ffffffff8027a784>] sys_delete_module+0x84/0x270
> > [<ffffffff8020c15b>] system_call_fastpath+0x16/0x1b
> > [<ffffffffffffffff>] 0xffffffffffffffff

Oleg, why does __create_workqueue_key() require cpu_maps_update_begin()?
Wouldn't get_online_cpus() be enough to freeze the online cpus?

Breaking the setup_lock -> cpu_add_remove_lock dependency seems
sufficient.

> > -> #4 (setup_lock){+.+.+.}:
> > [<ffffffff80271a64>] __lock_acquire+0xc64/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff8054e78c>] __mutex_lock_common+0x4c/0x3b0
> > [<ffffffff8054ebf6>] mutex_lock_nested+0x46/0x60
> > [<ffffffff80287af7>] stop_machine_create+0x17/0xb0
> > [<ffffffff80246f06>] disable_nonboot_cpus+0x26/0x130
> > [<ffffffff8027dd8d>] suspend_devices_and_enter+0xbd/0x1b0
> > [<ffffffff8027dff7>] enter_state+0x107/0x170
> > [<ffffffff8027e0f9>] state_store+0x99/0x100
> > [<ffffffff803abe17>] kobj_attr_store+0x17/0x20
> > [<ffffffff8033f1e9>] sysfs_write_file+0xd9/0x160
> > [<ffffffff802e1c88>] vfs_write+0xb8/0x180
> > [<ffffffff802e2771>] sys_write+0x51/0x90
> > [<ffffffff8020c15b>] system_call_fastpath+0x16/0x1b
> > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > -> #3 (dpm_list_mtx){+.+.+.}:
> > [<ffffffff80271a64>] __lock_acquire+0xc64/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff8054e78c>] __mutex_lock_common+0x4c/0x3b0
> > [<ffffffff8054ebf6>] mutex_lock_nested+0x46/0x60
> > [<ffffffff804532ff>] device_pm_add+0x1f/0xe0
> > [<ffffffff8044b9bf>] device_add+0x45f/0x570
> > [<ffffffffa007c578>] wiphy_register+0x158/0x280 [cfg80211]
> > [<ffffffffa017567c>] ieee80211_register_hw+0xbc/0x410 [mac80211]
> > [<ffffffffa01f7c5c>] iwl3945_pci_probe+0xa1c/0x1080 [iwl3945]
> > [<ffffffff803c4307>] local_pci_probe+0x17/0x20
> > [<ffffffff803c5458>] pci_device_probe+0x88/0xb0
> > [<ffffffff8044e1e9>] driver_probe_device+0x89/0x180
> > [<ffffffff8044e37b>] __driver_attach+0x9b/0xa0
> > [<ffffffff8044d67c>] bus_for_each_dev+0x6c/0xa0
> > [<ffffffff8044e03e>] driver_attach+0x1e/0x20
> > [<ffffffff8044d955>] bus_add_driver+0xd5/0x290
> > [<ffffffff8044e668>] driver_register+0x78/0x140
> > [<ffffffff803c56f6>] __pci_register_driver+0x66/0xe0
> > [<ffffffffa00bd05c>] 0xffffffffa00bd05c
> > [<ffffffff8020904f>] do_one_initcall+0x3f/0x1c0
> > [<ffffffff8027d071>] sys_init_module+0xb1/0x200
> > [<ffffffff8020c15b>] system_call_fastpath+0x16/0x1b
> > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > -> #2 (cfg80211_mutex){+.+.+.}:
> > [<ffffffff80271a64>] __lock_acquire+0xc64/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff8054e78c>] __mutex_lock_common+0x4c/0x3b0
> > [<ffffffff8054ebf6>] mutex_lock_nested+0x46/0x60
> > [<ffffffffa007e66a>] reg_todo+0x19a/0x590 [cfg80211]
> > [<ffffffff80258f18>] worker_thread+0x1e8/0x3a0
> > [<ffffffff8025dc3a>] kthread+0x5a/0xa0
> > [<ffffffff8020d23a>] child_rip+0xa/0x20
> > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > -> #1 (reg_work){+.+.+.}:
> > [<ffffffff80271a64>] __lock_acquire+0xc64/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff80258f12>] worker_thread+0x1e2/0x3a0
> > [<ffffffff8025dc3a>] kthread+0x5a/0xa0
> > [<ffffffff8020d23a>] child_rip+0xa/0x20
> > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > -> #0 (events){+.+.+.}:
> > [<ffffffff80271b36>] __lock_acquire+0xd36/0x10a0
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff802594bd>] cleanup_workqueue_thread+0x4d/0xd0
> > [<ffffffff8053fe79>] workqueue_cpu_callback+0xc9/0x10f
> > [<ffffffff805539a8>] notifier_call_chain+0x68/0xa0
> > [<ffffffff802630d6>] raw_notifier_call_chain+0x16/0x20
> > [<ffffffff8053d9ec>] _cpu_down+0x1cc/0x2d0
> > [<ffffffff80246f90>] disable_nonboot_cpus+0xb0/0x130
> > [<ffffffff8027dd8d>] suspend_devices_and_enter+0xbd/0x1b0
> > [<ffffffff8027dff7>] enter_state+0x107/0x170
> > [<ffffffff8027e0f9>] state_store+0x99/0x100
> > [<ffffffff803abe17>] kobj_attr_store+0x17/0x20
> > [<ffffffff8033f1e9>] sysfs_write_file+0xd9/0x160
> > [<ffffffff802e1c88>] vfs_write+0xb8/0x180
> > [<ffffffff802e2771>] sys_write+0x51/0x90
> > [<ffffffff8020c15b>] system_call_fastpath+0x16/0x1b
> > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > other info that might help us debug this:
> >
> > 4 locks held by pm-suspend/12129:
> > #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff8033f154>]
> > sysfs_write_file+0x44/0x160
> > #1: (pm_mutex){+.+.+.}, at: [<ffffffff8027df44>] enter_state+0x54/0x170
> > #2: (dpm_list_mtx){+.+.+.}, at: [<ffffffff80452747>] device_pm_lock+0x17/0x20
> > #3: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff80246e57>]
> > cpu_maps_update_begin+0x17/0x20
> >
> > stack backtrace:
> > Pid: 12129, comm: pm-suspend Not tainted 2.6.30-rc5-00097-gd665355 #59
> > Call Trace:
> > [<ffffffff8026fa3d>] print_circular_bug_tail+0x9d/0xe0
> > [<ffffffff80271b36>] __lock_acquire+0xd36/0x10a0
> > [<ffffffff80270000>] ? mark_lock+0x3e0/0x400
> > [<ffffffff80271f38>] lock_acquire+0x98/0x140
> > [<ffffffff80259496>] ? cleanup_workqueue_thread+0x26/0xd0
> > [<ffffffff802594bd>] cleanup_workqueue_thread+0x4d/0xd0
> > [<ffffffff80259496>] ? cleanup_workqueue_thread+0x26/0xd0
> > [<ffffffff802703ed>] ? trace_hardirqs_on+0xd/0x10
> > [<ffffffff8053fe79>] workqueue_cpu_callback+0xc9/0x10f
> > [<ffffffff8054acf1>] ? cpu_callback+0x12/0x280
> > [<ffffffff805539a8>] notifier_call_chain+0x68/0xa0
> > [<ffffffff802630d6>] raw_notifier_call_chain+0x16/0x20
> > [<ffffffff8053d9ec>] _cpu_down+0x1cc/0x2d0
> > [<ffffffff80246f90>] disable_nonboot_cpus+0xb0/0x130
> > [<ffffffff8027dd8d>] suspend_devices_and_enter+0xbd/0x1b0
> > [<ffffffff8027dff7>] enter_state+0x107/0x170
> > [<ffffffff8027e0f9>] state_store+0x99/0x100
> > [<ffffffff803abe17>] kobj_attr_store+0x17/0x20
> > [<ffffffff8033f1e9>] sysfs_write_file+0xd9/0x160
> > [<ffffffff802e1c88>] vfs_write+0xb8/0x180
> > [<ffffffff8029088c>] ? audit_syscall_entry+0x21c/0x240
> > [<ffffffff802e2771>] sys_write+0x51/0x90
> > [<ffffffff8020c15b>] system_call_fastpath+0x16/0x1b




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