.2356 and circular dependency.....

[Tom London]

After installing .2356 I get this each time I boot:
=======================================================
[ INFO: possible circular locking dependency detected ]
-------------------------------------------------------
S06cpuspeed/1620 is trying to acquire lock:
 (dbs_mutex){--..}, at: [<c060d6bb>] mutex_lock+0x21/0x24

but task is already holding lock:
 (cpucontrol){--..}, at: [<c060d6bb>] mutex_lock+0x21/0x24

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (cpucontrol){--..}:
       [<c043c546>] lock_acquire+0x4b/0x6d
       [<c060d51e>] __mutex_lock_slowpath+0xbf/0x23b
       [<c060d6bb>] mutex_lock+0x21/0x24
       [<c0440009>] __lock_cpu_hotplug+0x36/0x56
       [<c0440042>] lock_cpu_hotplug+0xa/0xc
       [<c04337de>] __create_workqueue+0x52/0x168
       [<f8e6b32e>] cpufreq_governor_dbs+0x9e/0x2cb [cpufreq_ondemand]
       [<c05a724b>] __cpufreq_governor+0x57/0xd8
       [<c05a7409>] __cpufreq_set_policy+0x13d/0x1a9
       [<c05a760c>] store_scaling_governor+0x128/0x151
       [<c05a6c67>] store+0x37/0x48
       [<c04ab4cc>] sysfs_write_file+0xab/0xd1
       [<c047248b>] vfs_write+0xab/0x157
       [<c0472ace>] sys_write+0x3b/0x60
       [<c0403f2f>] syscall_call+0x7/0xb

-> #0 (dbs_mutex){--..}:
       [<c043c546>] lock_acquire+0x4b/0x6d
       [<c060d51e>] __mutex_lock_slowpath+0xbf/0x23b
       [<c060d6bb>] mutex_lock+0x21/0x24
       [<f8e6b503>] cpufreq_governor_dbs+0x273/0x2cb [cpufreq_ondemand]
       [<c05a724b>] __cpufreq_governor+0x57/0xd8
       [<c05a7463>] __cpufreq_set_policy+0x197/0x1a9
       [<c05a760c>] store_scaling_governor+0x128/0x151
       [<c05a6c67>] store+0x37/0x48
       [<c04ab4cc>] sysfs_write_file+0xab/0xd1
       [<c047248b>] vfs_write+0xab/0x157
       [<c0472ace>] sys_write+0x3b/0x60
       [<c0403f2f>] syscall_call+0x7/0xb

other info that might help us debug this:

2 locks held by S06cpuspeed/1620:
 #0:  (&policy->lock){--..}, at: [<c060d6bb>] mutex_lock+0x21/0x24
 #1:  (cpucontrol){--..}, at: [<c060d6bb>] mutex_lock+0x21/0x24

stack backtrace:
 [<c0405167>] show_trace_log_lvl+0x54/0xfd
 [<c040571e>] show_trace+0xd/0x10
 [<c040583d>] dump_stack+0x19/0x1b
 [<c043b63d>] print_circular_bug_tail+0x59/0x64
 [<c043be35>] __lock_acquire+0x7ed/0x98d
 [<c043c546>] lock_acquire+0x4b/0x6d
 [<c060d51e>] __mutex_lock_slowpath+0xbf/0x23b
 [<c060d6bb>] mutex_lock+0x21/0x24
 [<f8e6b503>] cpufreq_governor_dbs+0x273/0x2cb [cpufreq_ondemand]
 [<c05a724b>] __cpufreq_governor+0x57/0xd8
 [<c05a7463>] __cpufreq_set_policy+0x197/0x1a9
 [<c05a760c>] store_scaling_governor+0x128/0x151
 [<c05a6c67>] store+0x37/0x48
 [<c04ab4cc>] sysfs_write_file+0xab/0xd1
 [<c047248b>] vfs_write+0xab/0x157
 [<c0472ace>] sys_write+0x3b/0x60
 [<c0403f2f>] syscall_call+0x7/0xb

BZ'ed here: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=197803

tom
-- 
Tom London