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Jan Kara 4d4f11c356 rq-qos: fix missed wake-ups in rq_qos_throttle try two 
commit 11c7aa0ddea8611007768d3e6b58d45dc60a19e1 upstream.

Commit 545fbd0775 ("rq-qos: fix missed wake-ups in rq_qos_throttle")
tried to fix a problem that a process could be sleeping in rq_qos_wait()
without anyone to wake it up. However the fix is not complete and the
following can still happen:

CPU1 (waiter1)		CPU2 (waiter2)		CPU3 (waker)
rq_qos_wait()		rq_qos_wait()
  acquire_inflight_cb() -> fails
			  acquire_inflight_cb() -> fails

						completes IOs, inflight
						  decreased
  prepare_to_wait_exclusive()
			  prepare_to_wait_exclusive()
  has_sleeper = !wq_has_single_sleeper() -> true as there are two sleepers
			  has_sleeper = !wq_has_single_sleeper() -> true
  io_schedule()		  io_schedule()

Deadlock as now there's nobody to wakeup the two waiters. The logic
automatically blocking when there are already sleepers is really subtle
and the only way to make it work reliably is that we check whether there
are some waiters in the queue when adding ourselves there. That way, we
are guaranteed that at least the first process to enter the wait queue
will recheck the waiting condition before going to sleep and thus
guarantee forward progress.

Fixes: 545fbd0775 ("rq-qos: fix missed wake-ups in rq_qos_throttle")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210607112613.25344-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2021-07-19 08:53:16 +02:00
..
partitions docs: admin-guide: add a series of orphaned documents 2019-07-15 11:03:02 -03:00
Kconfig blkcg: implement blk-iocost 2019-08-28 21:17:12 -06:00
Kconfig.iosched docs: block: convert to ReST 2019-07-15 09:20:27 -03:00
Makefile blkcg: implement blk-iocost 2019-08-28 21:17:12 -06:00
badblocks.c block: switch all files cleared marked as GPLv2 to SPDX tags 2019-04-30 16:11:57 -06:00
bfq-cgroup.c bfq: fix blkio cgroup leakage v4 2020-09-03 11:26:54 +02:00
bfq-iosched.c kyber: fix out of bounds access when preempted 2021-05-19 10:08:30 +02:00
bfq-iosched.h bfq: fix blkio cgroup leakage v4 2020-09-03 11:26:54 +02:00
bfq-wf2q.c bfq: fix blkio cgroup leakage v4 2020-09-03 11:26:54 +02:00
bio-integrity.c block: release bip in a right way in error path 2020-07-16 08:16:36 +02:00
bio.c block: only update parent bi_status when bio fail 2021-04-16 11:46:38 +02:00
blk-cgroup.c blk-cgroup: Use cond_resched() when destroy blkgs 2021-02-13 13:52:56 +01:00
blk-core.c Revert "Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT"" 2021-02-07 15:35:47 +01:00
blk-exec.c block: add SPDX tags to block layer files missing licensing information 2019-04-30 16:12:03 -06:00
blk-flush.c blk-mq: insert passthrough request into hctx->dispatch directly 2020-03-21 08:11:52 +01:00
blk-integrity.c block: centralize PI remapping logic to the block layer 2019-09-17 20:03:49 -06:00
blk-ioc.c block: Fix use-after-free issue accessing struct io_cq 2020-04-17 10:50:04 +02:00
blk-iocost.c blk-iocost: ioc_pd_free() shouldn't assume irq disabled 2020-09-09 19:12:35 +02:00
blk-iolatency.c blkcg: s/RQ_QOS_CGROUP/RQ_QOS_LATENCY/ 2019-08-28 21:17:08 -06:00
blk-lib.c block: fix 32 bit overflow in __blkdev_issue_discard() 2018-11-14 08:17:18 -07:00
blk-map.c block: fix memleak when __blk_rq_map_user_iov() is failed 2020-01-12 12:21:43 +01:00
blk-merge.c block: fix discard request merge 2021-07-14 16:53:19 +02:00
blk-mq-cpumap.c blk-mq: balance mapping between present CPUs and queues 2019-08-04 21:43:12 -06:00
blk-mq-debugfs-zoned.c block: Cleanup license notice 2019-01-17 21:21:40 -07:00
blk-mq-debugfs.c blk-mq-debugfs: update blk_queue_flag_name[] accordingly for new flags 2020-07-22 09:32:52 +02:00
blk-mq-debugfs.h blk-mq: no need to check return value of debugfs_create functions 2019-06-13 03:00:30 -06:00
blk-mq-pci.c block: Fix blk_mq_*_map_queues() kernel-doc headers 2019-05-31 15:12:34 -06:00
blk-mq-rdma.c block: Fix blk_mq_*_map_queues() kernel-doc headers 2019-05-31 15:12:34 -06:00
blk-mq-sched.c kyber: fix out of bounds access when preempted 2021-05-19 10:08:30 +02:00
blk-mq-sched.h block: only call sched requeue_request() for scheduled requests 2020-09-23 12:40:37 +02:00
blk-mq-sysfs.c blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue 2020-10-29 09:57:34 +01:00
blk-mq-tag.c blk-mq: introduce blk_mq_tagset_wait_completed_request() 2019-08-04 21:41:29 -06:00
blk-mq-tag.h Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
blk-mq-virtio.c block: Fix blk_mq_*_map_queues() kernel-doc headers 2019-05-31 15:12:34 -06:00
blk-mq.c blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:08:30 +02:00
blk-mq.h blk-mq: insert passthrough request into hctx->dispatch directly 2020-03-21 08:11:52 +01:00
blk-pm.c scsi: block: Fix a race in the runtime power management code 2021-01-06 14:48:37 +01:00
blk-pm.h block: remove the queue_lock indirection 2018-11-15 12:17:28 -07:00
blk-rq-qos.c rq-qos: fix missed wake-ups in rq_qos_throttle try two 2021-07-19 08:53:16 +02:00
blk-rq-qos.h block: fix race between adding/removing rq qos and normal IO 2021-07-14 16:53:18 +02:00
blk-settings.c blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 10:26:40 +01:00
blk-softirq.c block: remove a few unused exports 2018-11-15 12:13:25 -07:00
blk-stat.c block: add SPDX tags to block layer files missing licensing information 2019-04-30 16:12:03 -06:00
blk-stat.h block: deactivate blk_stat timer in wbt_disable_default() 2018-12-12 06:47:51 -07:00
blk-sysfs.c blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue 2020-10-29 09:57:34 +01:00
blk-throttle.c block: make rq sector size accessible for block stats 2019-09-15 16:02:08 -06:00
blk-timeout.c block: add SPDX tags to block layer files missing licensing information 2019-04-30 16:12:03 -06:00
blk-wbt.c blk-wbt: make sure throttle is enabled properly 2021-07-14 16:53:25 +02:00
blk-wbt.h blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() 2021-07-14 16:53:25 +02:00
blk-zoned.c block: Simplify REQ_OP_ZONE_RESET_ALL handling 2020-12-30 11:50:54 +01:00
blk.h block: fix memleak of bio integrity data 2020-01-26 10:01:09 +01:00
bounce.c block: remove the i argument to bio_for_each_segment_all 2019-04-30 09:26:13 -06:00
bsg-lib.c block: Fix the type of 'sts' in bsg_queue_rq() 2020-01-23 08:22:44 +01:00
bsg.c bsg: free the request before return error code 2021-03-04 10:26:22 +01:00
cmdline-parser.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat_ioctl.c compat_ioctl: block: handle BLKGETZONESZ/BLKGETNRZONES 2020-01-09 10:19:58 +01:00
elevator.c block: Fix elv_support_iosched() 2019-10-14 13:54:09 -06:00
genhd.c block: Suppress uevent for hidden device when removed 2021-03-30 14:35:23 +02:00
ioctl.c block: add SPDX tags to block layer files missing licensing information 2019-04-30 16:12:03 -06:00
ioprio.c docs: block: convert to ReST 2019-07-15 09:20:27 -03:00
kyber-iosched.c kyber: fix out of bounds access when preempted 2021-05-19 10:08:30 +02:00
mq-deadline.c kyber: fix out of bounds access when preempted 2021-05-19 10:08:30 +02:00
opal_proto.h block: sed-opal: Removed duplicate OPAL_METHOD_LENGTH definition 2019-08-20 09:34:49 -06:00
partition-generic.c block: fix use-after-free on gendisk 2019-04-22 09:48:12 -06:00
scsi_ioctl.c block: switch all files cleared marked as GPLv2 to SPDX tags 2019-04-30 16:11:57 -06:00
sed-opal.c block: sed-opal: fix sparse warning: convert __be64 data 2019-10-03 14:21:32 -06:00
t10-pi.c block: t10-pi: fix -Wswitch warning 2019-09-23 08:05:19 -06:00