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
badblocks.c
bfq-cgroup.c
bfq-iosched.c	kyber: fix out of bounds access when preempted	2021-05-19 10:08:30 +02:00
bfq-iosched.h
bfq-wf2q.c
bio-integrity.c
bio.c
blk-cgroup.c
blk-core.c
blk-exec.c
blk-flush.c
blk-integrity.c
blk-ioc.c
blk-iocost.c
blk-iolatency.c
blk-lib.c
blk-map.c
blk-merge.c	block: fix discard request merge	2021-07-14 16:53:19 +02:00
blk-mq-cpumap.c
blk-mq-debugfs-zoned.c
blk-mq-debugfs.c
blk-mq-debugfs.h
blk-mq-pci.c
blk-mq-rdma.c
blk-mq-sched.c	kyber: fix out of bounds access when preempted	2021-05-19 10:08:30 +02:00
blk-mq-sched.h
blk-mq-sysfs.c
blk-mq-tag.c
blk-mq-tag.h
blk-mq-virtio.c
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-pm.c
blk-pm.h
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-softirq.c
blk-stat.c
blk-stat.h
blk-sysfs.c
blk-throttle.c
blk-timeout.c
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
blk.h
bounce.c
bsg-lib.c
bsg.c
cmdline-parser.c
compat_ioctl.c
elevator.c
genhd.c
ioctl.c
ioprio.c
Kconfig
Kconfig.iosched
kyber-iosched.c	kyber: fix out of bounds access when preempted	2021-05-19 10:08:30 +02:00
Makefile
mq-deadline.c	kyber: fix out of bounds access when preempted	2021-05-19 10:08:30 +02:00
opal_proto.h
partition-generic.c
scsi_ioctl.c
sed-opal.c
t10-pi.c