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From: Jens Axboe <[email protected]>
To: Hao Xu <[email protected]>
Cc: [email protected], Pavel Begunkov <[email protected]>,
	Joseph Qi <[email protected]>
Subject: Re: [PATCH 4/4] io-wq: fix potential race of acct->nr_workers
Date: Sun, 12 Sep 2021 12:23:31 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 9/11/21 1:40 PM, Hao Xu wrote:
> Given max_worker is 1, and we currently have 1 running and it is
> exiting. There may be race like:
>  io_wqe_enqueue                   worker1
>                                no work there and timeout
>                                unlock(wqe->lock)
>  ->insert work
>                                -->io_worker_exit
>  lock(wqe->lock)
>  ->if(!nr_workers) //it's still 1
>  unlock(wqe->lock)
>     goto run_cancel
>                                   lock(wqe->lock)
>                                   nr_workers--
>                                   ->dec_running
>                                     ->worker creation fails
>                                   unlock(wqe->lock)
> 
> We enqueued one work but there is no workers, causes hung.

This one also looks good, applied.

-- 
Jens Axboe


      reply	other threads:[~2021-09-12 18:23 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-11 19:40 [PATCH 0/4] iowq fix Hao Xu
2021-09-11 19:40 ` [PATCH 1/4] io-wq: tweak return value of io_wqe_create_worker() Hao Xu
2021-09-12 18:10   ` Jens Axboe
2021-09-12 19:02     ` Hao Xu
2021-09-12 21:34       ` Jens Axboe
2021-09-13  6:37         ` Hao Xu
2021-09-11 19:40 ` [PATCH 2/4] io-wq: code clean " Hao Xu
2021-09-12 18:18   ` Jens Axboe
2021-09-13  8:30   ` Hao Xu
2021-09-11 19:40 ` [PATCH 3/4] io-wq: fix worker->refcount when creating worker in work exit Hao Xu
2021-09-11 22:13   ` Jens Axboe
2021-09-12  9:04     ` Hao Xu
2021-09-12 18:07       ` Jens Axboe
2021-09-11 19:40 ` [PATCH 4/4] io-wq: fix potential race of acct->nr_workers Hao Xu
2021-09-12 18:23   ` Jens Axboe [this message]

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