linux-kernel - [lockdep, sysfs]: lockdep compliant when chaging io schedulers

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Date:	Mon, 11 Jan 2010 18:54:16 +1100
From:	Dave Chinner <david@...morbit.com>
To:	linux-kernel@...r.kernel.org
Subject: [lockdep, sysfs]: lockdep compliant when chaging io schedulers


This output occurred on 2.6.33-rc3 when changing the schedler from cfq to noop.

[  129.838942] =============================================
[  129.839006] [ INFO: possible recursive locking detected ]
[  129.839006] 2.6.33-rc3-dgc #14                           
[  129.839006] ---------------------------------------------
[  129.839006] sh/3921 is trying to acquire lock:           
[  129.839006]  (s_active){++++.+}, at: [<ffffffff8117fa7e>] sysfs_remove_dir+0x7e/0xa0
[  129.839006]                                                                         
[  129.839006] but task is already holding lock:                                       
[  129.839006]  (s_active){++++.+}, at: [<ffffffff8117f4fd>] sysfs_get_active_two+0x3d/0x60
[  129.839006]                                                                             
[  129.839006] other info that might help us debug this:                                   
[  129.839006] 4 locks held by sh/3921:
[  129.839006]  #0:  (&buffer->mutex){+.+.+.}, at: [<ffffffff8117e0b9>] sysfs_write_file+0x49/0x150
[  129.839006]  #1:  (s_active){++++.+}, at: [<ffffffff8117f4fd>] sysfs_get_active_two+0x3d/0x60
[  129.839006]  #2:  (s_active){++++.+}, at: [<ffffffff8117f4e7>] sysfs_get_active_two+0x27/0x60
[  129.839006]  #3:  (&q->sysfs_lock){+.+.+.}, at: [<ffffffff813cb1e4>] queue_attr_store+0x54/0xb0
[  129.839006]
[  129.839006] stack backtrace:
[  129.839006] Pid: 3921, comm: sh Not tainted 2.6.33-rc3-dgc #14
[  129.839006] Call Trace:
[  129.839006]  [<ffffffff81084563>] __lock_acquire+0x1503/0x17a0
[  129.839006]  [<ffffffff81082ea2>] ? debug_check_no_locks_freed+0xa2/0x160
[  129.839006]  [<ffffffff81082795>] ? trace_hardirqs_on_caller+0x135/0x180
[  129.839006]  [<ffffffff810848ce>] lock_acquire+0xce/0x100
[  129.839006]  [<ffffffff8117fa7e>] ? sysfs_remove_dir+0x7e/0xa0
[  129.839006]  [<ffffffff8117f90c>] sysfs_addrm_finish+0xec/0x180
[  129.839006]  [<ffffffff8117fa7e>] ? sysfs_remove_dir+0x7e/0xa0
[  129.839006]  [<ffffffff810824c3>] ? mark_held_locks+0x73/0x90
[  129.839006]  [<ffffffff81073180>] ? cpu_clock+0x50/0x60
[  129.839006]  [<ffffffff8117fa7e>] sysfs_remove_dir+0x7e/0xa0
[  129.839006]  [<ffffffff813dd606>] kobject_del+0x16/0x40
[  129.839006]  [<ffffffff813c2246>] elv_iosched_store+0xf6/0x260
[  129.839006]  [<ffffffff813cb1fa>] queue_attr_store+0x6a/0xb0
[  129.839006]  [<ffffffff8117e149>] sysfs_write_file+0xd9/0x150
[  129.839006]  [<ffffffff8111c072>] vfs_write+0xb2/0xf0
[  129.839006]  [<ffffffff8111c1a5>] sys_write+0x55/0x90
[  129.839006]  [<ffffffff81002fdb>] system_call_fastpath+0x16/0x1b

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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