Messages in this thread | | | Date | Fri, 21 May 2010 14:14:45 -0700 | From | Andrew Morton <> | Subject | Re: possible circular locking dependency detected |
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On Thu, 20 May 2010 12:34:00 -0400 (EDT) Ciprian Docan <docan@eden.rutgers.edu> wrote:
> > Hi, > > I got the following in the dmesg: > > -------------------------------------------------------------------- > [ INFO: possible circular locking dependency detected ] > 2.6.33-rc8 #4 > ------------------------------------------------------- > fdisk/29231 is trying to acquire lock: > (&type->s_umount_key#47){++++..}, at: [<ffffffff810fb13c>] > get_super+0x5c/0xaf > > but task is already holding lock: > (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811f2df0>] > blkdev_ioctl+0x5c5/0x6b1 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (&bdev->bd_mutex){+.+.+.}: > [<ffffffff8106e65b>] __lock_acquire+0xb5d/0xd05 > [<ffffffff8106e8cf>] lock_acquire+0xcc/0xe9 > [<ffffffff81402d09>] __mutex_lock_common+0x4c/0x348 > [<ffffffff814030c9>] mutex_lock_nested+0x3e/0x43 > [<ffffffff8111f4a9>] __blkdev_put+0x34/0x16c > [<ffffffff8111f5f1>] blkdev_put+0x10/0x12 > [<ffffffff8112063b>] close_bdev_exclusive+0x24/0x2d > [<ffffffff810fbcaa>] get_sb_bdev+0xef/0x1a1 > [<ffffffffa0114189>] vfat_get_sb+0x18/0x1a [vfat] > [<ffffffff810fb8bc>] vfs_kern_mount+0xa9/0x168 > [<ffffffff810fb9e3>] do_kern_mount+0x4d/0xed > [<ffffffff81110f54>] do_mount+0x72f/0x7a6 > [<ffffffff81111053>] sys_mount+0x88/0xc2 > [<ffffffff8100236b>] system_call_fastpath+0x16/0x1b
vfs_kern_mount() holds s_umount. My brain isn't large enough to work out where that lock was taken, yet it's so obvious that no code comments were needed. Sigh. Might be down under sget().
vfs_kern_mount() ends up calling into __blkdev_put(), which takes bd_mutex.
> -> #0 (&type->s_umount_key#47){++++..}: > [<ffffffff8106e505>] __lock_acquire+0xa07/0xd05 > [<ffffffff8106e8cf>] lock_acquire+0xcc/0xe9 > [<ffffffff81403450>] down_read+0x51/0x84 > [<ffffffff810fb13c>] get_super+0x5c/0xaf > [<ffffffff8111facd>] fsync_bdev+0x18/0x48 > [<ffffffff811f433c>] invalidate_partition+0x25/0x42 > [<ffffffff8114bda2>] rescan_partitions+0x37/0x3a7 > [<ffffffff811f2dff>] blkdev_ioctl+0x5d4/0x6b1 > [<ffffffff8111eca4>] block_ioctl+0x37/0x3b > [<ffffffff811060d0>] vfs_ioctl+0x32/0xa6 > [<ffffffff81106650>] do_vfs_ioctl+0x490/0x4d6 > [<ffffffff811066ec>] sys_ioctl+0x56/0x79 > [<ffffffff8100236b>] system_call_fastpath+0x16/0x1b
blkdev_reread_part() takes bd_mutex then does rescan_partitions ->invalidate_partition ->fsync_bdev ->get_super (takes s_umount for reading)
> other info that might help us debug this: > > 1 lock held by fdisk/29231: > #0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811f2df0>] > blkdev_ioctl+0x5c5/0x6b1 > > stack backtrace: > Pid: 29231, comm: fdisk Not tainted 2.6.33-rc8 #4 > Call Trace: > [<ffffffff8106d6dc>] print_circular_bug+0xa8/0xb6 > [<ffffffff8106e505>] __lock_acquire+0xa07/0xd05 > [<ffffffff81062009>] ? sched_clock_local+0x1c/0x82 > [<ffffffff8106e8cf>] lock_acquire+0xcc/0xe9 > [<ffffffff810fb13c>] ? get_super+0x5c/0xaf > [<ffffffff8106b936>] ? lock_release_holdtime+0x2c/0xdb > [<ffffffff81403450>] down_read+0x51/0x84 > [<ffffffff810fb13c>] ? get_super+0x5c/0xaf > [<ffffffff810fb13c>] get_super+0x5c/0xaf > [<ffffffff8111facd>] fsync_bdev+0x18/0x48 > [<ffffffff811f433c>] invalidate_partition+0x25/0x42 > [<ffffffff81402c8e>] ? mutex_trylock+0x12a/0x159 > [<ffffffff8114bda2>] rescan_partitions+0x37/0x3a7 > [<ffffffff8106d0c9>] ? trace_hardirqs_on+0xd/0xf > [<ffffffff811f2df0>] ? blkdev_ioctl+0x5c5/0x6b1 > [<ffffffff811f2dff>] blkdev_ioctl+0x5d4/0x6b1 > [<ffffffff8106d098>] ? trace_hardirqs_on_caller+0x118/0x13c > [<ffffffff8111eca4>] block_ioctl+0x37/0x3b > [<ffffffff811060d0>] vfs_ioctl+0x32/0xa6 > [<ffffffff81106650>] do_vfs_ioctl+0x490/0x4d6 > [<ffffffff811066ec>] sys_ioctl+0x56/0x79 > [<ffffffff8102f9bd>] ? __wake_up+0x22/0x4d > [<ffffffff8100236b>] system_call_fastpath+0x16/0x1b > ------------------------------------------------------------------------- > > Kernel version used: 2.6.33-rc8 #4. I do not remember the exact steps, but > I was trying to format an USB stick using the fdisk. Please let me know if > you need additional informations. Thank you. >
So yup, that's ab/ba deadlockable. I cannot immediately see any change which might have caused that. Tejun has been mucking with the partitions code recently but nothing leaps out at me.
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