From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f173.google.com (mail-qt1-f173.google.com [209.85.160.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9CAD7C8CB; Mon, 15 May 2023 12:26:51 +0000 (UTC) Received: by mail-qt1-f173.google.com with SMTP id d75a77b69052e-3f41b73104eso32808001cf.3; Mon, 15 May 2023 05:26:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1684153610; x=1686745610; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=frVvBnuP2+i1aJfoXn+uOQ4Dz2/3JLy5AwDGkoiWkAA=; b=fHaGi/NwOVxcobMw6IFO5ss/FvKw2r+7FXIEJ85Odymwvh1N649DR1PnMuPFs/755N 8aE+UKy6gqPCSoh6fUUCmr5XSvycsKRwa8ALWDUlN4t7TT9FeaOO1KLD9m1PAEH2+kOW OHWALp9MR6n95db+1TPk+5JG1AdHFqy2zery0rj0/3cgPe7zgs5ifehXM5t0SFE8Oi7H qjnEffPyLYFbb5+1esjlFWScYEvF0TvOfQhRUkuAFtByu0fF6s6OyxnviCKQlyGmGDyg w3ZNjxaVlTiKUZL7t7l5C3alt95WvCedpHaGf8sadF03BKjW26Iz1KHM3Yxfk2xfKReS t+bw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684153610; x=1686745610; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=frVvBnuP2+i1aJfoXn+uOQ4Dz2/3JLy5AwDGkoiWkAA=; b=j7ysipj6tyjrmZDX6cTnfrvOQb3TKZ9b8UEbdTfYFY7hL7jwPnCj2Vb1L7nPNAts+r pYbnaU+mBDyq3HWCntoZRtAGKc2GDHagevEyO2vvL7n0S21ETH8b1vSQZRcF5Fya2BDR 9xtuu8fmhbHEN+KIfPogDnVcKbwPmgtv4Pr9A1JmjV8rgVpXlmpbFEAre4QtgbyafxYQ BnomS00RZJHr9sVv5hBEqa9rMcxPpTpmd6rwAKwQom0ck8Ux8RhfWry8uRSZdPHiEq5R EgPdMDS7PhAFxPKvVyzpK5+fk2ydLkjKH07Zi5ogeAJF1EHQTTWU9giukO6fUY5dmlYp IEbw== X-Gm-Message-State: AC+VfDzT4jUWWGumseO9zOs6Avs1NTZcbpeUMSxhF9sZa+8ShgIwvLit FmoBLg/8xVwaw5e2R1kGkZA= X-Google-Smtp-Source: ACHHUZ6UVQqt/Q5Q7FdQgoJCVn2vJlZj9ekfWfTM2bVhtPYCZhqh96pfA590HhUR4eBOOfm4HFeeHQ== X-Received: by 2002:a05:622a:414:b0:3f3:895b:6161 with SMTP id n20-20020a05622a041400b003f3895b6161mr44618826qtx.65.1684153610369; Mon, 15 May 2023 05:26:50 -0700 (PDT) Received: from tian-Alienware-15-R4.fios-router.home (pool-173-77-254-84.nycmny.fios.verizon.net. [173.77.254.84]) by smtp.gmail.com with ESMTPSA id m24-20020aed27d8000000b003f364778b2bsm5395733qtg.4.2023.05.15.05.26.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 May 2023 05:26:49 -0700 (PDT) From: Tian Lan To: hare@suse.de Cc: axboe@kernel.dk, horms@kernel.org, linux-block@vger.kernel.org, lkp@intel.com, llvm@lists.linux.dev, ming.lei@redhat.com, oe-kbuild-all@lists.linux.dev, tian.lan@twosigma.com, tilan7663@gmail.com Subject: [PATCH] blk-mq: fix blk_mq_hw_ctx active request accounting Date: Mon, 15 May 2023 08:26:43 -0400 Message-Id: <20230515122643.597546-1-tilan7663@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <1c9fc9df-817c-e6cb-1375-2013c0c5a9bb@suse.de> References: <1c9fc9df-817c-e6cb-1375-2013c0c5a9bb@suse.de> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tian Lan The nr_active counter continues to increase over time which causes the blk_mq_get_tag to hang until the thread is rescheduled to a different core despite there are still tags available. kernel-stack INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:inboundIORe state:D stack:0 pid:3014879 ppid:4557 flags:0x00000000 Call Trace: __schedule+0x351/0xa20 scheduler+0x5d/0xe0 io_schedule+0x42/0x70 blk_mq_get_tag+0x11a/0x2a0 ? dequeue_task_stop+0x70/0x70 __blk_mq_alloc_requests+0x191/0x2e0 kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before __blk_mq_free_request being called. 320 320 kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 b'__blk_mq_free_request+0x1 [kernel]' b'bt_iter+0x50 [kernel]' b'blk_mq_queue_tag_busy_iter+0x318 [kernel]' b'blk_mq_timeout_work+0x7c [kernel]' b'process_one_work+0x1c4 [kernel]' b'worker_thread+0x4d [kernel]' b'kthread+0xe6 [kernel]' b'ret_from_fork+0x1f [kernel]' The issue is caused by the difference between blk_mq_free_request() and blk_mq_end_request_batch() wrt. when to call __blk_mq_dec_active_requests(). The former does it before calling req_ref_put_and_test(), and the latter decreases the active request after req_ref_put_and_test(). - Fixes: f794f3351f26 ("block: add support for blk_mq_end_request_batch()") Signed-off-by: Tian Lan Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke --- block/blk-mq.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index f6dad0886a2f..850bfb844ed2 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -683,6 +683,10 @@ static void __blk_mq_free_request(struct request *rq) blk_crypto_free_request(rq); blk_pm_mark_last_busy(rq); rq->mq_hctx = NULL; + + if (rq->rq_flags & RQF_MQ_INFLIGHT) + __blk_mq_dec_active_requests(hctx); + if (rq->tag != BLK_MQ_NO_TAG) blk_mq_put_tag(hctx->tags, ctx, rq->tag); if (sched_tag != BLK_MQ_NO_TAG) @@ -694,15 +698,11 @@ static void __blk_mq_free_request(struct request *rq) void blk_mq_free_request(struct request *rq) { struct request_queue *q = rq->q; - struct blk_mq_hw_ctx *hctx = rq->mq_hctx; if ((rq->rq_flags & RQF_ELVPRIV) && q->elevator->type->ops.finish_request) q->elevator->type->ops.finish_request(rq); - if (rq->rq_flags & RQF_MQ_INFLIGHT) - __blk_mq_dec_active_requests(hctx); - if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq))) laptop_io_completion(q->disk->bdi); -- 2.25.1