Re: 2.6.33-rc3 -- INFO: possible recursive locking -- (s_active){++++.+}, at: [<c10d2941>] sysfs_hash_and_remove+0x3d/0x4f

[Rafael J. Wysocki]

On Sunday 10 January 2010, Eric W. Biederman wrote:
> AmÃrico Wang <xiyou.wangcong@xxxxxxxxx> writes:
> 
> > On Sun, Jan 10, 2010 at 4:47 PM, AmÃrico Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> >>
> >> On Wed, Jan 06, 2010 at 07:54:59AM -0500, Miles Lane wrote:
> >> >[ 6967.926563] ACPI: Preparing to enter system sleep state S3
> >> >[ 6967.956156] Disabling non-boot CPUs ...
> >> >[ 6967.970401]
> >> >[ 6967.970408] =============================================
> >> >[ 6967.970419] [ INFO: possible recursive locking detected ]
> >> >[ 6967.970431] 2.6.33-rc2-git6 #27
> >> >[ 6967.970439] ---------------------------------------------
> >> >[ 6967.970450] pm-suspend/22147 is trying to acquire lock:
> >> >[ 6967.970460]  (s_active){++++.+}, at: [<c10d2941>]
> >> >sysfs_hash_and_remove+0x3d/0x4f
> >> >[ 6967.970493]
> >> >[ 6967.970497] but task is already holding lock:
> >> >[ 6967.970506]  (s_active){++++.+}, at: [<c10d4110>]
> >> >sysfs_get_active_two+0x16/0x36
> >> >[ 6967.970531]
> >> >[ 6967.970535] other info that might help us debug this:
> >> >[ 6967.970547] 6 locks held by pm-suspend/22147:
> >> >[ 6967.970556]  #0:  (&buffer->mutex){+.+.+.}, at: [<c10d2ff3>]
> >> >sysfs_write_file+0x25/0xeb
> >> >[ 6967.970584]  #1:  (s_active){++++.+}, at: [<c10d4110>]
> >> >sysfs_get_active_two+0x16/0x36
> >> >[ 6967.970612]  #2:  (s_active){++++.+}, at: [<c10d411b>]
> >> >sysfs_get_active_two+0x21/0x36
> >> >[ 6967.970639]  #3:  (pm_mutex){+.+.+.}, at: [<c1056f00>] enter_state+0x26/0x114
> >> >[ 6967.970668]  #4:  (cpu_add_remove_lock){+.+.+.}, at: [<c102ea10>]
> >> >cpu_maps_update_begin+0xf/0x11
> >> >[ 6967.970697]  #5:  (cpu_hotplug.lock){+.+.+.}, at: [<c102ea3e>]
> >> >cpu_hotplug_begin+0x1d/0x40
> >> >[ 6967.970724]
> >> >[ 6967.970728] stack backtrace:
> >> >[ 6967.970740] Pid: 22147, comm: pm-suspend Not tainted 2.6.33-rc2-git6 #27
> >> >[ 6967.970751] Call Trace:
> >> >[ 6967.970771]  [<c12cc9bf>] ? printk+0xf/0x18
> >> >[ 6967.970791]  [<c104dcdb>] __lock_acquire+0x817/0xb6d
> >> >[ 6967.970812]  [<c104cbb2>] ? mark_held_locks+0x43/0x5b
> >> >[ 6967.970831]  [<c104cf4c>] ? debug_check_no_locks_freed+0xfd/0x107
> >> >[ 6967.970851]  [<c104ce1a>] ? trace_hardirqs_on_caller+0x108/0x130
> >> >[ 6967.970871]  [<c104e08d>] lock_acquire+0x5c/0x73
> >> >[ 6967.970890]  [<c10d2941>] ? sysfs_hash_and_remove+0x3d/0x4f
> >> >[ 6967.970910]  [<c10d3ee6>] sysfs_addrm_finish+0x9a/0xfe
> >> >[ 6967.970929]  [<c10d2941>] ? sysfs_hash_and_remove+0x3d/0x4f
> >> >[ 6967.970953]  [<c10d2941>] sysfs_hash_and_remove+0x3d/0x4f
> >> >[ 6967.970974]  [<c10d4c11>] sysfs_remove_group+0x52/0x81
> >> >[ 6967.970993]  [<c12cab5d>] mc_cpu_callback+0x73/0x9a
> >> >[ 6967.971014]  [<c10427d0>] notifier_call_chain+0x51/0x78
> >> >[ 6967.971034]  [<c104285c>] __raw_notifier_call_chain+0xe/0x10
> >> >[ 6967.971054]  [<c12c094b>] _cpu_down+0x7a/0x235
> >> >[ 6967.971074]  [<c102eab9>] disable_nonboot_cpus+0x58/0xe0
> >> >[ 6967.971093]  [<c1056e20>] suspend_devices_and_enter+0xb9/0x173
> >> >[ 6967.971094]  [<c1056fa2>] enter_state+0xc8/0x114
> >> >[ 6967.971094]  [<c1056855>] state_store+0x93/0xa7
> >> >[ 6967.971094]  [<c10567c2>] ? state_store+0x0/0xa7
> >> >[ 6967.971094]  [<c1140595>] kobj_attr_store+0x16/0x22
> >> >[ 6967.971094]  [<c10d308e>] sysfs_write_file+0xc0/0xeb
> >> >[ 6967.971094]  [<c10d2fce>] ? sysfs_write_file+0x0/0xeb
> >> >[ 6967.971094]  [<c109511c>] vfs_write+0x80/0xdf
> >> >[ 6967.971094]  [<c109520f>] sys_write+0x3b/0x5d
> >> >[ 6967.971094]  [<c1002897>] sysenter_do_call+0x12/0x36
> >> >[ 6967.973262] CPU 1 is now offline
> >> >[ 6967.973271] lockdep: fixing up alternatives.
> >>
> >> Hmmm, does reverting commit 846f99749ab68b help?
> >>
> >
> > Of course it will help, but the problem is not that. That patch helps
> > us to detect such a problem... I am still investigating. :-/
> 
> This looks like this is triggered by a write to a sysfs file,
> so the solution is probably to call schedule_work so the
> suspend can happen outside the context of sysfs.
> 
> The typical scenario that triggers this is:
> - A lock is held while removing a sysfs attribute.
> - The same lock is grabbed inside the sysfs attribute.
> 
> I think we do that with the cpu_hotplug.lock
> 
> In this case it looks like this might be a reach around scenario where
> we try and remove the sysfs attribute that triggered the suspend.

We don't do that.

Rafael
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