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Merge branch 'workqueue/for-5.16-fixes' into workqueue/for-5.17 

for-5.16-fixes contains two subtle race conditions which were introduced by
scheduler side code cleanups. The branch didn't get pushed out, so merge
into for-5.17.
This commit is contained in:
Tejun Heo 2022-01-10 07:54:04 -10:00
parent 84f91c62d6 45c753f5f2
commit 2a8ab0fbd1
1 changed files with 21 additions and 1 deletions
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22
kernel/workqueue.c
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@ -864,8 +864,17 @@ void wq_worker_running(struct task_struct *task)
if (!worker->sleeping)
return;
/*
* If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
* and the nr_running increment below, we may ruin the nr_running reset
* and leave with an unexpected pool->nr_running == 1 on the newly unbound
* pool. Protect against such race.
*/
preempt_disable();
if (!(worker->flags & WORKER_NOT_RUNNING))
atomic_inc(&worker->pool->nr_running);
preempt_enable();
worker->sleeping = 0;
}
@ -898,6 +907,16 @@ void wq_worker_sleeping(struct task_struct *task)
worker->sleeping = 1;
raw_spin_lock_irq(&pool->lock);
/*
* Recheck in case unbind_workers() preempted us. We don't
* want to decrement nr_running after the worker is unbound
* and nr_running has been reset.
*/
if (worker->flags & WORKER_NOT_RUNNING) {
raw_spin_unlock_irq(&pool->lock);
return;
}
/*
* The counterpart of the following dec_and_test, implied mb,
* worklist not empty test sequence is in insert_work().
@ -1526,7 +1545,8 @@ out:
* @work: work to queue
*
* We queue the work to a specific CPU, the caller must ensure it
* can't go away.
* can't go away. Callers that fail to ensure that the specified
* CPU cannot go away will execute on a randomly chosen CPU.
*
* Return: %false if @work was already on a queue, %true otherwise.
*/