Asias He 5e5cfac0c6 block: Mitigate lock unbalance caused by lock switching ... Commit 777eb1bf15 disconnects externally supplied queue_lock before blk_drain_queue(). Switching the lock would introduce lock unbalance because theads which have taken the external lock might unlock the internal lock in the during the queue drain. This patch mitigate this by disconnecting the lock after the queue draining since queue draining makes a lot of request_queue users go away. However, please note, this patch only makes the problem less likely to happen. Anyone who still holds a ref might try to issue a new request on a dead queue after the blk_cleanup_queue() finishes draining, the lock unbalance might still happen in this case. ===================================== [ BUG: bad unlock balance detected! ] 3.4.0+ #288 Not tainted ------------------------------------- fio/17706 is trying to release lock (&(&q->__queue_lock)->rlock) at: [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380 but there are no more locks to release! other info that might help us debug this: 1 lock held by fio/17706: #0: (&(&vblk->lock)->rlock){......}, at: [<ffffffff81327f1a>] get_request_wait+0x19a/0x250 stack backtrace: Pid: 17706, comm: fio Not tainted 3.4.0+ #288 Call Trace: [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff810dea49>] print_unlock_inbalance_bug+0xf9/0x100 [<ffffffff810dfe4f>] lock_release_non_nested+0x1df/0x330 [<ffffffff811dae24>] ? dio_bio_end_aio+0x34/0xc0 [<ffffffff811d6935>] ? bio_check_pages_dirty+0x85/0xe0 [<ffffffff811daea1>] ? dio_bio_end_aio+0xb1/0xc0 [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff810e0079>] lock_release+0xd9/0x250 [<ffffffff81a74553>] _raw_spin_unlock_irq+0x23/0x40 [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380 [<ffffffff81328faa>] generic_make_request+0xca/0x100 [<ffffffff81329056>] submit_bio+0x76/0xf0 [<ffffffff8115470c>] ? set_page_dirty_lock+0x3c/0x60 [<ffffffff811d69e1>] ? bio_set_pages_dirty+0x51/0x70 [<ffffffff811dd1a8>] do_blockdev_direct_IO+0xbf8/0xee0 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff811dd4e5>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff811d92e7>] blkdev_direct_IO+0x57/0x60 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff8114c6ae>] generic_file_aio_read+0x70e/0x760 [<ffffffff810df7c5>] ? __lock_acquire+0x215/0x5a0 [<ffffffff811e9924>] ? aio_run_iocb+0x54/0x1a0 [<ffffffff8114bfa0>] ? grab_cache_page_nowait+0xc0/0xc0 [<ffffffff811e82cc>] aio_rw_vect_retry+0x7c/0x1e0 [<ffffffff811e8250>] ? aio_fsync+0x30/0x30 [<ffffffff811e9936>] aio_run_iocb+0x66/0x1a0 [<ffffffff811ea9b0>] do_io_submit+0x6f0/0xb80 [<ffffffff8134de2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff811eae50>] sys_io_submit+0x10/0x20 [<ffffffff81a7c9e9>] system_call_fastpath+0x16/0x1b Changes since v2: Update commit log to explain how the code is still broken even if we delay the lock switching after the drain. Changes since v1: Update commit log as Tejun suggested. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>		2012-06-15 08:46:22 +02:00
..
partitions	s390/dasd: re-prioritize partition detection message	2012-05-16 14:42:51 +02:00
blk-cgroup.c	blkcg: drop local variable @q from blkg_destroy()	2012-06-06 08:35:31 +02:00
blk-cgroup.h	blkcg: use radix tree to index blkgs from blkcg	2012-04-20 10:06:40 +02:00
blk-core.c	block: Mitigate lock unbalance caused by lock switching	2012-06-15 08:46:22 +02:00
blk-exec.c	block: add missing blk_queue_dead() checks	2011-12-14 00:33:37 +01:00
blk-flush.c	blk-flush: move the queue kick into	2011-10-24 16:24:31 +02:00
blk-integrity.c	block: add export.h to files using EXPORT_SYMBOL/THIS_MODULE macros	2011-10-31 19:31:12 -04:00
blk-ioc.c	block: avoid infinite loop in get_task_io_context()	2012-05-31 13:39:05 +02:00
blk-iopoll.c
blk-lib.c	block: fix patch import error in max_discard_sectors check	2011-07-23 20:34:59 +02:00
blk-map.c	block: re-use existing 'reading' variable instead of checking direction again	2011-12-21 15:27:24 +01:00
blk-merge.c	block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions	2012-02-08 09:19:38 +01:00
blk-settings.c	block: Introduce blk_set_stacking_limits function	2012-01-11 16:27:11 +01:00
blk-softirq.c	sched, block: Unify cache detection	2012-01-27 13:28:48 +01:00
blk-sysfs.c	blkcg: unify blkg's for blkcg policies	2012-03-06 21:27:23 +01:00
blk-tag.c	block: fix blk_queue_end_tag()	2011-12-29 09:16:28 +01:00
blk-throttle.c	blkcg: tg_stats_alloc_lock is an irq lock	2012-05-23 12:16:21 +02:00
blk-timeout.c	fault-injection: add ability to export fault_attr in arbitrary directory	2011-08-03 14:25:20 -10:00
blk.h	Merge branch 'for-3.5' of ../cgroup into block/for-3.5/core-merged	2012-04-01 12:55:00 -07:00
bsg-lib.c	block: Change module.h -> export.h in bsg-lib.c	2011-10-31 19:31:13 -04:00
bsg.c	bsg: fix sysfs link remove warning	2012-02-08 20:02:03 +01:00
cfq-iosched.c	block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHED	2012-06-04 10:02:29 +02:00
compat_ioctl.c	block: Add BLKROTATIONAL ioctl	2012-01-11 16:29:31 +01:00
deadline-iosched.c	elevator: make elevator_init_fn() return 0/-errno	2012-03-06 21:27:21 +01:00
elevator.c	blkcg: implement per-queue policy activation	2012-04-20 10:06:06 +02:00
genhd.c	block: fix buffer overflow when printing partition UUIDs	2012-05-15 08:22:04 +02:00
ioctl.c	Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-block	2012-01-15 12:24:45 -08:00
Kconfig	move fs/partitions to block/	2012-01-03 22:54:06 -05:00
Kconfig.iosched	blkcg: make CONFIG_BLK_CGROUP bool	2012-03-06 21:27:21 +01:00
Makefile	separate partition format handling from generic code	2012-01-03 22:54:06 -05:00
noop-iosched.c	elevator: make elevator_init_fn() return 0/-errno	2012-03-06 21:27:21 +01:00
partition-generic.c	block: Fix NULL pointer dereference in sd_revalidate_disk	2012-03-02 10:38:33 +01:00
scsi_ioctl.c	block: fail SCSI passthrough ioctls on partition devices	2012-01-14 15:07:24 -08:00