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SubjectRe: [PATCH] workqueue: Handle race between wake up and rebind
Hello, Neeraj.

On Mon, Jan 15, 2018 at 02:08:12PM +0530, Neeraj Upadhyay wrote:
> - kworker/0:0 gets chance to run on cpu1; while processing
> a work, it goes to sleep. However, it does not decrement
> pool->nr_running. This is because WORKER_REBOUND (NOT_
> RUNNING) flag was cleared, when worker entered worker_

Do you mean that because REBOUND was set?

> thread().
>
> Worker 0 runs on cpu1
> worker_thread()
> process_one_work()
> wq_worker_sleeping()
> if (worker->flags & WORKER_NOT_RUNNING)
> return NULL;
> if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
> <Does not decrement nr_running>
>
> - After this, when kworker/0:0 wakes up, this time on its
> bounded cpu cpu0, it increments pool->nr_running again.
> So, pool->nr_running becomes 2.

Why is it suddenly 2? Who made it one on the account of the kworker?

Do you see this happening? Or better, is there a (semi) reliable
repro for this issue?

Thanks.

--
tejun

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