Commit 680e58e7 authored Mar 07, 2019 by Johannes Weiner Committed by Patrick Daly Mar 20, 2019

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>
Change-Id: Iba9616c0193affb09f04daa59efb5a76f8d8f637
Git-commit: 4b0470027528ba98f9617f4ceba328de71d2fe49
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm


Signed-off-by: Patrick Daly <pdaly@codeaurora.org>

parent ab214458

kernel/workqueue.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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.