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TencentOS-kernel/kernel/sched
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Jan Kara f1b43174a0 rq-qos: fix missed wake-ups in rq_qos_throttle try two 
Commit 545fbd0775ba ("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.

UPSTREAM COMMIT:
11c7aa0ddea8611007768d3e6b58d45dc60a19e1

Fixes: 545fbd0775ba ("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>
 		2022-04-12 16:58:30 +08:00
..
Makefile Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
autogroup.c sched: disable sched_auto_group by default 2021-10-29 08:50:28 +00:00
autogroup.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
clock.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
completion.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
core.c Add cfs bandwidth burst statistics 2022-03-02 10:48:06 +08:00
cpuacct.c cgroupfs: support for proc and sys 2021-11-01 15:00:06 +08:00
cpudeadline.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cpudeadline.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cpufreq.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cpufreq_schedutil.c sched/uclamp: Protect uclamp fast path code with static key 2021-03-16 16:34:54 +08:00
cpupri.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cpupri.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cputime.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
deadline.c sched/deadline: Fix sched_dl_global_validate() 2021-03-16 16:42:38 +08:00
debug.c sched/debug: Fix cgroup_path[] serialization 2021-05-20 16:07:54 +08:00
fair.c kthread: Fix PF_KTHREAD vs to_kthread() race 2022-03-02 10:48:07 +08:00
features.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
idle.c rcu/nocb: Perform deferred wake up before last idle's need_resched() check 2021-04-12 12:52:37 +08:00
isolation.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
loadavg.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
membarrier.c sched/membarrier: fix missing local execution of ipi_sync_rq_state() 2021-04-12 12:53:11 +08:00
pelt.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
pelt.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
psi.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
rt.c sched: Defend cfs and rt bandwidth quota against overflow 2021-03-16 16:29:33 +08:00
sched-pelt.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
sched.h Add cfs bandwidth burst statistics 2022-03-02 10:48:06 +08:00
stats.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
stats.h sli/cpu: introduce longsys check 2021-10-29 06:51:52 +00:00
stop_task.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
swait.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
topology.c sched: correct SD_flags returned by tl->sd_flags() 2021-03-16 16:33:12 +08:00
wait.c rq-qos: fix missed wake-ups in rq_qos_throttle try two 2022-04-12 16:58:30 +08:00
wait_bit.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00