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Date: Sun, 12 Sep 2010 22:43:23 +0200
From: Arnd Bergmann <arnd@...db.de>
To: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: lockdep warning: events vs. bd_mutex
I got the warning below, which apparently tells me that a work queue doing
sd_probe_async ends up calling invalidate_bdev, which calls flush_work,
and that is something that is not allowed from workqueue context.
The change leading to this seems to be fa4b9074cd "buffer: make
invalidate_bdev() drain all percpu LRU add caches", which Tejun
introduced in 2.6.35 as a bug fix.
AFAICT, this happened when I plugged in a USB flash drive while
running last Friday's linux-next kernel.
Arnd
[ 464.601121] sdd: sdd1
[ 464.601126] sdd: p1 size 260288 extends beyond EOD, enabling native capacity
[ 464.601244]
[ 464.601244] =======================================================
[ 464.601288] [ INFO: possible circular locking dependency detected ]
[ 464.601317] 2.6.36-rc3-next-20100910+ #44
[ 464.601337] -------------------------------------------------------
[ 464.601366] kworker/u:5/1184 is trying to acquire lock:
[ 464.601392] (events){+.+.+.}, at: [<ffffffff810567a3>] flush_work+0xb8/0x143
[ 464.602109]
[ 464.602109] but task is already holding lock:
[ 464.602109] (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8111e0db>] __blkdev_get+0x54/0x32f
[ 464.602109]
[ 464.602109] which lock already depends on the new lock.
[ 464.602109]
[ 464.602109]
[ 464.602109] the existing dependency chain (in reverse order) is:
[ 464.602109]
[ 464.602109] -> #3 (&bdev->bd_mutex){+.+.+.}:
[ 464.602109] [<ffffffff8106dad4>] lock_acquire+0xe3/0x110
[ 464.602109] [<ffffffff813f5b5b>] __mutex_lock_common+0x4b/0x35e
[ 464.602109] [<ffffffff813f5f32>] mutex_lock_nested+0x3e/0x43
[ 464.602109] [<ffffffff8111d7df>] revalidate_disk+0x4b/0x73
[ 464.602109] [<ffffffff812a969f>] sd_rescan+0x27/0x34
[ 464.602109] [<ffffffff812a1be6>] scsi_rescan_device+0x82/0x98
[ 464.602109] [<ffffffff812b53e5>] ata_scsi_dev_rescan+0x8d/0xf4
[ 464.602109] [<ffffffff810558b0>] process_one_work+0x232/0x399
[ 464.602109] [<ffffffff8105759a>] worker_thread+0x13b/0x251
[ 464.602109] [<ffffffff8105ace8>] kthread+0x82/0x8a
[ 464.602109] [<ffffffff81003a64>] kernel_thread_helper+0x4/0x10
[ 464.602109]
[ 464.602109] -> #2 (&ap->scsi_scan_mutex){+.+.+.}:
[ 464.602109] [<ffffffff8106dad4>] lock_acquire+0xe3/0x110
[ 464.602109] [<ffffffff813f5b5b>] __mutex_lock_common+0x4b/0x35e
[ 464.602109] [<ffffffff813f5f32>] mutex_lock_nested+0x3e/0x43
[ 464.602109] [<ffffffff812b538e>] ata_scsi_dev_rescan+0x36/0xf4
[ 464.602109] [<ffffffff810558b0>] process_one_work+0x232/0x399
[ 464.602109] [<ffffffff8105759a>] worker_thread+0x13b/0x251
[ 464.602109] [<ffffffff8105ace8>] kthread+0x82/0x8a
[ 464.602109] [<ffffffff81003a64>] kernel_thread_helper+0x4/0x10
[ 464.602109]
[ 464.602109] -> #1 ((&ap->scsi_rescan_task)){+.+.+.}:
[ 464.602109] [<ffffffff8106dad4>] lock_acquire+0xe3/0x110
[ 464.602109] [<ffffffff8105587a>] process_one_work+0x1fc/0x399
[ 464.602109] [<ffffffff8105759a>] worker_thread+0x13b/0x251
[ 464.602109] [<ffffffff8105ace8>] kthread+0x82/0x8a
[ 464.602109] [<ffffffff81003a64>] kernel_thread_helper+0x4/0x10
[ 464.602109]
[ 464.602109] -> #0 (events){+.+.+.}:
[ 464.602109] [<ffffffff8106d6e9>] __lock_acquire+0xa30/0xd38
[ 464.602109] [<ffffffff8106dad4>] lock_acquire+0xe3/0x110
[ 464.602109] [<ffffffff810567e7>] flush_work+0xfc/0x143
[ 464.602109] [<ffffffff81056903>] schedule_on_each_cpu+0xd5/0x115
[ 464.602109] [<ffffffff810c6f06>] lru_add_drain_all+0x15/0x17
[ 464.602109] [<ffffffff81118b93>] invalidate_bdev+0x2d/0x3f
[ 464.602109] [<ffffffff8111d16c>] __invalidate_device+0x48/0x53
[ 464.602109] [<ffffffff811ebf1d>] invalidate_partition+0x2d/0x42
[ 464.602109] [<ffffffff8114ac31>] rescan_partitions+0x63/0x40e
[ 464.602109] [<ffffffff8111e2f0>] __blkdev_get+0x269/0x32f
[ 464.602109] [<ffffffff8111e3c6>] blkdev_get+0x10/0x12
[ 464.602109] [<ffffffff8114a35d>] register_disk+0xdc/0x13f
[ 464.602109] [<ffffffff811eb5f0>] add_disk+0xaf/0x10b
[ 464.602109] [<ffffffff812abd2b>] sd_probe_async+0x129/0x1cd
[ 464.602109] [<ffffffff81061847>] async_run_entry_fn+0xa8/0x15b
[ 464.602109] [<ffffffff810558b0>] process_one_work+0x232/0x399
[ 464.602109] [<ffffffff8105759a>] worker_thread+0x13b/0x251
[ 464.602109] [<ffffffff8105ace8>] kthread+0x82/0x8a
[ 464.602109] [<ffffffff81003a64>] kernel_thread_helper+0x4/0x10
[ 464.602109]
[ 464.602109] other info that might help us debug this:
[ 464.602109]
[ 464.602109] 3 locks held by kworker/u:5/1184:
[ 464.602109] #0: (events_unbound){+.+.+.}, at: [<ffffffff81055825>] process_one_work+0x1a7/0x399
[ 464.602109] #1: ((&entry->work)){+.+.+.}, at: [<ffffffff81055825>] process_one_work+0x1a7/0x399
[ 464.602109] #2: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8111e0db>] __blkdev_get+0x54/0x32f
[ 464.602109]
[ 464.602109] stack backtrace:
[ 464.602109] Pid: 1184, comm: kworker/u:5 Not tainted 2.6.36-rc3-next-20100910+ #44
[ 464.602109] Call Trace:
[ 464.602109] [<ffffffff8106c6b5>] print_circular_bug+0xbd/0xce
[ 464.602109] [<ffffffff8106d6e9>] __lock_acquire+0xa30/0xd38
[ 464.602109] [<ffffffff8106dad4>] lock_acquire+0xe3/0x110
[ 464.602109] [<ffffffff810567a3>] ? flush_work+0xb8/0x143
[ 464.602109] [<ffffffff8106bffd>] ? trace_hardirqs_on_caller+0x11d/0x141
[ 464.602109] [<ffffffff810567e7>] flush_work+0xfc/0x143
[ 464.602109] [<ffffffff810567a3>] ? flush_work+0xb8/0x143
[ 464.602109] [<ffffffff8106bffd>] ? trace_hardirqs_on_caller+0x11d/0x141
[ 464.602109] [<ffffffff810553a0>] ? wq_barrier_func+0x0/0x14
[ 464.602109] [<ffffffff810c7120>] ? lru_add_drain_per_cpu+0x0/0x10
[ 464.602109] [<ffffffff81056903>] schedule_on_each_cpu+0xd5/0x115
[ 464.602109] [<ffffffff810c6f06>] lru_add_drain_all+0x15/0x17
[ 464.602109] [<ffffffff81118b93>] invalidate_bdev+0x2d/0x3f
[ 464.602109] [<ffffffff8111d16c>] __invalidate_device+0x48/0x53
[ 464.602109] [<ffffffff811ebf1d>] invalidate_partition+0x2d/0x42
[ 464.602109] [<ffffffff8114ac31>] rescan_partitions+0x63/0x40e
[ 464.602109] [<ffffffff812aa2bc>] ? sd_open+0x11f/0x147
[ 464.602109] [<ffffffff8111e2f0>] __blkdev_get+0x269/0x32f
[ 464.602109] [<ffffffff8106179f>] ? async_run_entry_fn+0x0/0x15b
[ 464.602109] [<ffffffff8111e3c6>] blkdev_get+0x10/0x12
[ 464.602109] [<ffffffff8114a35d>] register_disk+0xdc/0x13f
[ 464.602109] [<ffffffff8106179f>] ? async_run_entry_fn+0x0/0x15b
[ 464.602109] [<ffffffff811eb5f0>] add_disk+0xaf/0x10b
[ 464.602109] [<ffffffff812abd2b>] sd_probe_async+0x129/0x1cd
[ 464.602109] [<ffffffff81061847>] async_run_entry_fn+0xa8/0x15b
[ 464.602109] [<ffffffff810558b0>] process_one_work+0x232/0x399
[ 464.602109] [<ffffffff81055825>] ? process_one_work+0x1a7/0x399
[ 464.602109] [<ffffffff8105759a>] worker_thread+0x13b/0x251
[ 464.602109] [<ffffffff8105745f>] ? worker_thread+0x0/0x251
[ 464.602109] [<ffffffff8105ace8>] kthread+0x82/0x8a
[ 464.602109] [<ffffffff81003a64>] kernel_thread_helper+0x4/0x10
[ 464.602109] [<ffffffff813f7710>] ? restore_args+0x0/0x30
[ 464.602109] [<ffffffff8105ac66>] ? kthread+0x0/0x8a
[ 464.602109] [<ffffffff81003a60>] ? kernel_thread_helper+0x0/0x10
[ 464.735104] sd 9:0:0:0: [sdd] Assuming drive cache: write through
[ 464.743108] sdd: sdd1
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