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| author | Johannes Weiner <hannes@cmpxchg.org> | 2019-03-07 16:29:30 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-03-07 18:32:01 -0800 |
| commit | 4b0470027528ba98f9617f4ceba328de71d2fe49 (patch) | |
| tree | 396305027606c8acc1418ac9d2475b5a370aa9ff /kernel | |
| parent | 6eb3c3d0a52dca337e327ae8868ca1f44a712e02 (diff) | |
| download | lwn-4b0470027528ba98f9617f4ceba328de71d2fe49.tar.gz lwn-4b0470027528ba98f9617f4ceba328de71d2fe49.zip | |
kernel: workqueue: clarify wq_worker_last_func() caller requirements
This function can only be called safely from very specific scheduler
contexts. Document those.
Link: http://lkml.kernel.org/r/20190206150528.31198-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 56814902bc56..d51c37dd9422 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -920,6 +920,16 @@ 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. |