This function can only be called safely from very specific scheduler contexts. Document those.
Suggested-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Johannes Weiner <han...@cmpxchg.org> --- kernel/workqueue.c | 10 ++++++++++ 1 file changed, 10 insertions(+) Andrew suggested including the explanations that came up during the code review in the function doc. As the function has since been merged, sending as follow-up for 5.1. Thanks! diff --git a/kernel/workqueue.c b/kernel/workqueue.c index fc5d23d752a5..23a67b9430da 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -918,6 +918,16 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task) * CONTEXT: * spin_lock_irq(rq->lock) * + * This function is called during schedule() when a kworker is going + * to sleep. It's used by psi to identify aggregation workers during + * dequeuing, to allow periodic aggregation to shut-off when that + * worker is the last task in the system or cgroup to go to sleep. + * + * As this function doesn't involve any workqueue-related locking, it + * only returns stable values when called from inside the scheduler's + * queuing and dequeuing paths, when @task, which must be a kworker, + * is guaranteed to not be processing any works. + * * Return: * The last work function %current executed as a worker, NULL if it * hasn't executed any work yet. -- 2.20.1
