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Sun, 23 May 2021 13:07:44 -0700 (PDT) Subject: =?UTF-8?B?UmU6IOWbnuWkjTogW3N5emJvdF0gS0FTQU46IHVzZS1hZnRlci1mcmVl?= =?UTF-8?Q?_Read_in_io=5fworker=5fhandle=5fwork?= From: Pavel Begunkov To: "Zhang, Qiang" , syzbot , "axboe@kernel.dk" , "io-uring@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "syzkaller-bugs@googlegroups.com" References: <0000000000008224bf05c2a8a78b@google.com> Message-ID: <7243f420-58c5-60e4-6c8f-c16a90766c0c@gmail.com> Date: Sun, 23 May 2021 21:07:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 5/22/21 1:55 AM, Pavel Begunkov wrote: > On 5/21/21 9:45 AM, Zhang, Qiang wrote: > [...] >> It looks like >> thread iou-wrk-28796 in io-wq(A) access wqe in the wait queue(data->hash->wait), but this wqe has been free due to the destruction of another io-wq(B). >> >> Should we after wait for all iou-wrk thread exit in the io-wq， remove wqe from the waiting queue (data->hash->wait). prevent some one wqe belonging to this io-wq , may be still existing in the (data->hash->wait)queue before releasing. > > The guess looks reasonable, it's likely a problem. > Not sure about the diff, it seems racy but I need to > take a closer look to say for sure It looks sensible, please send a patch >> look forward to your opinion. >> >> --- a/fs/io-wq.c >> +++ b/fs/io-wq.c >> @@ -1003,13 +1003,17 @@ static void io_wq_exit_workers(struct io_wq *wq) >> struct io_wqe *wqe = wq->wqes[node]; >> >> io_wq_for_each_worker(wqe, io_wq_worker_wake, NULL); >> - spin_lock_irq(&wq->hash->wait.lock); >> - list_del_init(&wq->wqes[node]->wait.entry); >> - spin_unlock_irq(&wq->hash->wait.lock); >> } >> rcu_read_unlock(); >> io_worker_ref_put(wq); >> wait_for_completion(&wq->worker_done); >> + for_each_node(node) { >> + struct io_wqe *wqe = wq->wqes[node]; >> + >> + spin_lock_irq(&wq->hash->wait.lock); >> + list_del_init(&wq->wqes[node]->wait.entry); >> + spin_unlock_irq(&wq->hash->wait.lock); >> + } >> put_task_struct(wq->task); >> wq->task = NULL; >> } > -- Pavel Begunkov