From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91077C433DF for ; Wed, 20 May 2020 13:16:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B9EA20756 for ; Wed, 20 May 2020 13:16:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726436AbgETNQp (ORCPT ); Wed, 20 May 2020 09:16:45 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:44194 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbgETNQo (ORCPT ); Wed, 20 May 2020 09:16:44 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04397;MF=xiaoguang.wang@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0Tz6U4jg_1589980590; Received: from 30.225.32.165(mailfrom:xiaoguang.wang@linux.alibaba.com fp:SMTPD_---0Tz6U4jg_1589980590) by smtp.aliyun-inc.com(127.0.0.1); Wed, 20 May 2020 21:16:30 +0800 Subject: Re: [PATCH] io_uring: reset -EBUSY error when io sq thread is waken up To: Jens Axboe , io-uring@vger.kernel.org Cc: joseph.qi@linux.alibaba.com References: <20200520044059.2308-1-xiaoguang.wang@linux.alibaba.com> <5d119755-01dc-e3e5-f15c-8002e26a8487@kernel.dk> From: Xiaoguang Wang Message-ID: <56da287b-adab-d9dd-e727-2d39dfdd4b7d@linux.alibaba.com> Date: Wed, 20 May 2020 21:16:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <5d119755-01dc-e3e5-f15c-8002e26a8487@kernel.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org hi, > On 5/19/20 10:40 PM, Xiaoguang Wang wrote: >> In io_sq_thread(), currently if we get an -EBUSY error, we will >> won't clear it again, which will result in io_sq_thread() will >> never have a chance to submit sqes again. Below test program test.c >> can reveal this bug: >> >> int main(int argc, char *argv[]) >> { >> struct io_uring ring; >> int i, fd, ret; >> struct io_uring_sqe *sqe; >> struct io_uring_cqe *cqe; >> struct iovec *iovecs; >> void *buf; >> struct io_uring_params p; >> >> if (argc < 2) { >> printf("%s: file\n", argv[0]); >> return 1; >> } >> >> memset(&p, 0, sizeof(p)); >> p.flags = IORING_SETUP_SQPOLL; >> ret = io_uring_queue_init_params(4, &ring, &p); >> if (ret < 0) { >> fprintf(stderr, "queue_init: %s\n", strerror(-ret)); >> return 1; >> } >> >> fd = open(argv[1], O_RDONLY | O_DIRECT); >> if (fd < 0) { >> perror("open"); >> return 1; >> } >> >> iovecs = calloc(10, sizeof(struct iovec)); >> for (i = 0; i < 10; i++) { >> if (posix_memalign(&buf, 4096, 4096)) >> return 1; >> iovecs[i].iov_base = buf; >> iovecs[i].iov_len = 4096; >> } >> >> ret = io_uring_register_files(&ring, &fd, 1); >> if (ret < 0) { >> fprintf(stderr, "%s: register %d\n", __FUNCTION__, ret); >> return ret; >> } >> >> for (i = 0; i < 10; i++) { >> sqe = io_uring_get_sqe(&ring); >> if (!sqe) >> break; >> >> io_uring_prep_readv(sqe, 0, &iovecs[i], 1, 0); >> sqe->flags |= IOSQE_FIXED_FILE; >> >> ret = io_uring_submit(&ring); >> sleep(1); >> printf("submit %d\n", i); >> } >> >> for (i = 0; i < 10; i++) { >> io_uring_wait_cqe(&ring, &cqe); >> printf("receive: %d\n", i); >> if (cqe->res != 4096) { >> fprintf(stderr, "ret=%d, wanted 4096\n", cqe->res); >> ret = 1; >> } >> io_uring_cqe_seen(&ring, cqe); >> } >> >> close(fd); >> io_uring_queue_exit(&ring); >> return 0; >> } >> sudo ./test testfile >> above command will hang on the tenth request, to fix this bug, when io >> sq_thread is waken up, we reset the variable 'ret' to be zero. >> >> Signed-off-by: Xiaoguang Wang >> --- >> fs/io_uring.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 6e51140a5722..747de5cdf38a 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -6045,6 +6045,8 @@ static int io_sq_thread(void *data) >> finish_wait(&ctx->sqo_wait, &wait); >> >> ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP; >> + if (ret == -EBUSY) >> + ret = 0; >> continue; >> } >> finish_wait(&ctx->sqo_wait, &wait); > > How about just unconditionally clearing it? There's nothing we > need to preserve at this point, it should just get set to zero > regardless of the value. OK, agree, will send a new version soon, thanks. Regards, Xiaoguang Wang >