Messages in this thread Patch in this message | | | Subject | Re: [BUG?] possible recursive locking detected (blkdev_open) | From | Peter Zijlstra <> | Date | Fri, 18 Aug 2006 12:35:21 +0200 |
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(partial CC list from commit 663d440eaa496db903cc58be04b9b602ba45e43b)
On Wed, 2006-08-09 at 07:57 +0200, Rolf Eike Beer wrote: > ============================================= > [ INFO: possible recursive locking detected ] > --------------------------------------------- > parted/7929 is trying to acquire lock: > (&bdev->bd_mutex){--..}, at: [<c105eb8d>] __blkdev_put+0x1e/0x13c > > but task is already holding lock: > (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > > other info that might help us debug this: > 1 lock held by parted/7929: > #0: (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > stack backtrace: > [<c1003aad>] show_trace_log_lvl+0x58/0x15b > [<c100495f>] show_trace+0xd/0x10 > [<c1004979>] dump_stack+0x17/0x1a > [<c102dee5>] __lock_acquire+0x753/0x99c > [<c102e3b0>] lock_acquire+0x4a/0x6a > [<c1204501>] mutex_lock_nested+0xc8/0x20c > [<c105eb8d>] __blkdev_put+0x1e/0x13c > [<c105ecc4>] blkdev_put+0xa/0xc > [<c105f18a>] do_open+0x336/0x3a8 > [<c105f21b>] blkdev_open+0x1f/0x4c > [<c1057b40>] __dentry_open+0xc7/0x1aa > [<c1057c91>] nameidata_to_filp+0x1c/0x2e > [<c1057cd1>] do_filp_open+0x2e/0x35 > [<c1057dd7>] do_sys_open+0x38/0x68 > [<c1057e33>] sys_open+0x16/0x18 > [<c1002845>] sysenter_past_esp+0x56/0x8d
OK, I'm having a look here; its all new to me so bear with me.
blkdev_open() calls do_open(bdev, ...,BD_MUTEX_NORMAL) and takes mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_NORMAL)
then something fails, and we're thrown to:
out_first: where if (bdev != bdev->bd_contains) blkdev_put(bdev->bd_contains) which is __blkdev_put(bdev->bd_contains, BD_MUTEX_NORMAL) which does mutex_lock_nested(&bdev->bd_contains->bd_mutex, BD_MUTEX_NORMAL) <--- lockdep trigger
When going to out_first, dbev->bd_contains is either bdev or whole, and since we take the branch it must be whole. So it seems to me the following patch would be the right one:
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- fs/block_dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-2.6/fs/block_dev.c =================================================================== --- linux-2.6.orig/fs/block_dev.c +++ linux-2.6/fs/block_dev.c @@ -980,7 +980,7 @@ out_first: bdev->bd_disk = NULL; bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; if (bdev != bdev->bd_contains) - blkdev_put(bdev->bd_contains); + __blkdev_put(bdev->bd_contains, BD_MUTEX_WHOLE); bdev->bd_contains = NULL; put_disk(disk); module_put(owner);
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