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Tue, 30 Mar 2021 11:44:39 -0700 (PDT) Subject: Re: [PATCH 1/1] io-wq: forcefully cancel on io-wq destroy From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org References: <822eeb713e57efe8960a7f3a7c11dbef1fcbf4e4.1617129472.git.asml.silence@gmail.com> Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <2f85b4f1-80f3-44e7-60ff-c3f2e2fb93ab@gmail.com> Date: Tue, 30 Mar 2021 19:40:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <822eeb713e57efe8960a7f3a7c11dbef1fcbf4e4.1617129472.git.asml.silence@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 30/03/2021 19:38, Pavel Begunkov wrote: > [ 491.222908] INFO: task thread-exit:2490 blocked for more than 122 seconds. > [ 491.222957] Call Trace: > [ 491.222967] __schedule+0x36b/0x950 > [ 491.222985] schedule+0x68/0xe0 > [ 491.222994] schedule_timeout+0x209/0x2a0 > [ 491.223003] ? tlb_flush_mmu+0x28/0x140 > [ 491.223013] wait_for_completion+0x8b/0xf0 > [ 491.223023] io_wq_destroy_manager+0x24/0x60 > [ 491.223037] io_wq_put_and_exit+0x18/0x30 > [ 491.223045] io_uring_clean_tctx+0x76/0xa0 > [ 491.223061] __io_uring_files_cancel+0x1b9/0x2e0 > [ 491.223068] ? blk_finish_plug+0x26/0x40 > [ 491.223085] do_exit+0xc0/0xb40 > [ 491.223099] ? syscall_trace_enter.isra.0+0x1a1/0x1e0 > [ 491.223109] __x64_sys_exit+0x1b/0x20 > [ 491.223117] do_syscall_64+0x38/0x50 > [ 491.223131] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 491.223177] INFO: task iou-mgr-2490:2491 blocked for more than 122 seconds. > [ 491.223194] Call Trace: > [ 491.223198] __schedule+0x36b/0x950 > [ 491.223206] ? pick_next_task_fair+0xcf/0x3e0 > [ 491.223218] schedule+0x68/0xe0 > [ 491.223225] schedule_timeout+0x209/0x2a0 > [ 491.223236] wait_for_completion+0x8b/0xf0 > [ 491.223246] io_wq_manager+0xf1/0x1d0 > [ 491.223255] ? recalc_sigpending+0x1c/0x60 > [ 491.223265] ? io_wq_cpu_online+0x40/0x40 > [ 491.223272] ret_from_fork+0x22/0x30 > > When io-wq worker exits and sees IO_WQ_BIT_EXIT it tries not cancel all > left requests but to execute them, hence we may wait for the exiting > task for long until someone pushes it, e.g. with SIGKILL. Actively > cancel pending work items on io-wq destruction. The trace is from slightly modified thread-exit, and it doesn't hang forever, but can be killed with ctrl+c or whatever. Also, predictably breaks thread-exit test. > > note: io_run_cancel() moved up without any changes. > > Signed-off-by: Pavel Begunkov > --- > fs/io-wq.c | 50 +++++++++++++++++++++++++++++++++++--------------- > 1 file changed, 35 insertions(+), 15 deletions(-) > > diff --git a/fs/io-wq.c b/fs/io-wq.c > index 7434eb40ca8c..5fa5e0fd40d6 100644 > --- a/fs/io-wq.c > +++ b/fs/io-wq.c > @@ -342,6 +342,20 @@ static void io_wait_on_hash(struct io_wqe *wqe, unsigned int hash) > spin_unlock(&wq->hash->wait.lock); > } > > +static struct io_wq_work *io_get_work_all(struct io_wqe *wqe) > + __must_hold(wqe->lock) > +{ > + struct io_wq_work_list *list = &wqe->work_list; > + struct io_wq_work_node *node = list->first; > + int i; > + > + list->first = list->last = NULL; > + for (i = 0; i < IO_WQ_NR_HASH_BUCKETS; i++) > + wqe->hash_tail[i] = NULL; > + > + return node ? container_of(node, struct io_wq_work, list) : NULL; > +} > + > static struct io_wq_work *io_get_next_work(struct io_wqe *wqe) > __must_hold(wqe->lock) > { > @@ -410,6 +424,17 @@ static void io_assign_current_work(struct io_worker *worker, > > static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work); > > +static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe) > +{ > + struct io_wq *wq = wqe->wq; > + > + do { > + work->flags |= IO_WQ_WORK_CANCEL; > + wq->do_work(work); > + work = wq->free_work(work); > + } while (work); > +} > + > static void io_worker_handle_work(struct io_worker *worker) > __releases(wqe->lock) > { > @@ -518,11 +543,17 @@ static int io_wqe_worker(void *data) > } > > if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) { > + struct io_wq_work *work, *next; > + > raw_spin_lock_irq(&wqe->lock); > - if (!wq_list_empty(&wqe->work_list)) > - io_worker_handle_work(worker); > - else > - raw_spin_unlock_irq(&wqe->lock); > + work = io_get_all_items(wqe); > + raw_spin_unlock_irq(&wqe->lock); > + > + while (work) { > + next = wq_next_work(work); > + io_get_work_all(work, wqe); > + work = next; > + } > } > > io_worker_exit(worker); > @@ -748,17 +779,6 @@ static int io_wq_manager(void *data) > do_exit(0); > } > > -static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe) > -{ > - struct io_wq *wq = wqe->wq; > - > - do { > - work->flags |= IO_WQ_WORK_CANCEL; > - wq->do_work(work); > - work = wq->free_work(work); > - } while (work); > -} > - > static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work) > { > unsigned int hash; > -- Pavel Begunkov