From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) (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 04BD41FD0; Mon, 15 May 2023 05:54:36 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 64C1221D41; Mon, 15 May 2023 05:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1684130069; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2g2SRYrfL0FsqPNDX6p//ghRaOiZy0Uhnjt4q+fH5MU=; b=FROqecaKMuexOzGH3mwY7yBusf7OEzWAIDx7xq4W9uNUasoKrYVvn11VOtuO3zOYqblpSL K602eifFSNA9mxY5Sh0JyrYX05KSUlPKn/xBxclkbp0aPPsmMBb7bpset2lQyAGgb/K4IA PP7AK6VfRbQptcBo4GQVu140Ayb1ekI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1684130069; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2g2SRYrfL0FsqPNDX6p//ghRaOiZy0Uhnjt4q+fH5MU=; b=BUr6UGSB4yeTZb7D2IAkK+LUs1tT3SMVmySry2rX+5bf7i+31GT5JSMi2E3jNuUQVCPYXM saejdp1e0wkf+eBQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 367BF13499; Mon, 15 May 2023 05:54:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id uKZvDBXJYWSAYwAAMHmgww (envelope-from ); Mon, 15 May 2023 05:54:29 +0000 Message-ID: <1c9fc9df-817c-e6cb-1375-2013c0c5a9bb@suse.de> Date: Mon, 15 May 2023 07:54:28 +0200 Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH] blk-mq: fix blk_mq_hw_ctx active request accounting Content-Language: en-US To: Tian Lan , ming.lei@redhat.com Cc: axboe@kernel.dk, horms@kernel.org, linux-block@vger.kernel.org, lkp@intel.com, llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, tian.lan@twosigma.com References: <20230514145328.595743-1-tilan7663@gmail.com> From: Hannes Reinecke In-Reply-To: <20230514145328.595743-1-tilan7663@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 5/14/23 16:53, Tian Lan wrote: > 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 > --- > block/blk-mq.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman