Messages in this thread | | | Date | Thu, 16 Sep 2021 15:53:18 +0800 | From | Ming Lei <> | Subject | Re: [PATCH v7 2/6] nbd: make sure request completion won't concurrent |
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On Wed, Sep 15, 2021 at 05:20:06PM +0800, Yu Kuai wrote: > commit cddce0116058 ("nbd: Aovid double completion of a request") > try to fix that nbd_clear_que() and recv_work() can complete a > request concurrently. However, the problem still exists: > > t1 t2 t3 > > nbd_disconnect_and_put > flush_workqueue > recv_work > blk_mq_complete_request > blk_mq_complete_request_remote -> this is true > WRITE_ONCE(rq->state, MQ_RQ_COMPLETE) > blk_mq_raise_softirq > blk_done_softirq > blk_complete_reqs > nbd_complete_rq > blk_mq_end_request > blk_mq_free_request > WRITE_ONCE(rq->state, MQ_RQ_IDLE) > nbd_clear_que > blk_mq_tagset_busy_iter > nbd_clear_req > __blk_mq_free_request > blk_mq_put_tag > blk_mq_complete_request -> complete again > > There are three places where request can be completed in nbd: > recv_work(), nbd_clear_que() and nbd_xmit_timeout(). Since they > all hold cmd->lock before completing the request, it's easy to > avoid the problem by setting and checking a cmd flag. > > Signed-off-by: Yu Kuai <yukuai3@huawei.com> > ---
Reviewed-by: Ming Lei <ming.lei@redhat.com>
-- Ming
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