From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F8773128C0 for ; Fri, 14 Nov 2025 11:41:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763120499; cv=none; b=YwHw/RVdoROSZlGw4YblF67Hw5524bDkhrLh/rLg+YUOPoYkSHLJyZLSl+NB9rH6HbhkMPxGu3E9I12L8atZlJarR5kXGCyaUXP3YLzKKgp5YyxmvwgldU7diXwzOCWVkjpCMVyZPBb/G+vBXxCYmuTemmNOpQZmvDQ9H9zxRAQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763120499; c=relaxed/simple; bh=kCJBv8ahljEGJCgwGSf0ssnmdx2vcHNSme18qHXru5k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MeazNLUbJ40q12YNPmxLoB9v6JFkr/MlzRbMF/MGD4WLNywWxi4MzrFJytAGuYO15FBtlQAeIqeEywRClXXgqaJfm8stYdTcM6m6CroTxzXvD+DMQlG36sDUakf+GxFrHHbz1yg4roA88VVbK7jwq56qQ5HhwaGYKZjRLTW9CIE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=A4t/parn; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="A4t/parn" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763120497; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2ecMm9O07ms9TEHe9nKCQPh9xB4OigdxXlVPBpq5cVA=; b=A4t/parnHtmsDWKYTETvfEadeCkQMBkwhwGgI/XJjbXHzja4R1Hq14P60oY6wGxiM9NXGc RmVN2bguHIO4iQ2yAjQzASep1JHaMO03gh5sur32ajdPHCRPVEfsmx7Ry1SPlrQnDdsfao 00YR1Ln0PqvL5lXL3ZB2mdmrC26n+UY= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-569-h-GUjrY7N3iEzqqK9ssNmQ-1; Fri, 14 Nov 2025 06:41:34 -0500 X-MC-Unique: h-GUjrY7N3iEzqqK9ssNmQ-1 X-Mimecast-MFC-AGG-ID: h-GUjrY7N3iEzqqK9ssNmQ_1763120492 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0EA791800452; Fri, 14 Nov 2025 11:41:32 +0000 (UTC) Received: from fedora (unknown [10.72.116.81]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5FFFF300018D; Fri, 14 Nov 2025 11:41:18 +0000 (UTC) Date: Fri, 14 Nov 2025 19:41:14 +0800 From: Ming Lei To: Mohamed Khalfella Cc: Jens Axboe , Keith Busch , Sagi Grimberg , Chaitanya Kulkarni , Casey Chen , Vikas Manocha , Yuanyuan Zhong , Hannes Reinecke , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] nvme: Convert tag_list mutex to rwsemaphore to avoid deadlock Message-ID: References: <20251113202320.2530531-1-mkhalfella@purestorage.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251113202320.2530531-1-mkhalfella@purestorage.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Thu, Nov 13, 2025 at 12:23:20PM -0800, Mohamed Khalfella wrote: > blk_mq_{add,del}_queue_tag_set() functions add and remove queues from > tagset, the functions make sure that tagset and queues are marked as > shared when two or more queues are attached to the same tagset. > Initially a tagset starts as unshared and when the number of added > queues reaches two, blk_mq_add_queue_tag_set() marks it as shared along > with all the queues attached to it. When the number of attached queues > drops to 1 blk_mq_del_queue_tag_set() need to mark both the tagset and > the remaining queues as unshared. > > Both functions need to freeze current queues in tagset before setting on > unsetting BLK_MQ_F_TAG_QUEUE_SHARED flag. While doing so, both functions > hold set->tag_list_lock mutex, which makes sense as we do not want > queues to be added or deleted in the process. This used to work fine > until commit 98d81f0df70c ("nvme: use blk_mq_[un]quiesce_tagset") > made the nvme driver quiesce tagset instead of quiscing individual > queues. blk_mq_quiesce_tagset() does the job and quiesce the queues in > set->tag_list while holding set->tag_list_lock also. > > This results in deadlock between two threads with these stacktraces: > > __schedule+0x48e/0xed0 > schedule+0x5a/0xc0 > schedule_preempt_disabled+0x11/0x20 > __mutex_lock.constprop.0+0x3cc/0x760 > blk_mq_quiesce_tagset+0x26/0xd0 > nvme_dev_disable_locked+0x77/0x280 [nvme] > nvme_timeout+0x268/0x320 [nvme] > blk_mq_handle_expired+0x5d/0x90 > bt_iter+0x7e/0x90 > blk_mq_queue_tag_busy_iter+0x2b2/0x590 > ? __blk_mq_complete_request_remote+0x10/0x10 > ? __blk_mq_complete_request_remote+0x10/0x10 > blk_mq_timeout_work+0x15b/0x1a0 > process_one_work+0x133/0x2f0 > ? mod_delayed_work_on+0x90/0x90 > worker_thread+0x2ec/0x400 > ? mod_delayed_work_on+0x90/0x90 > kthread+0xe2/0x110 > ? kthread_complete_and_exit+0x20/0x20 > ret_from_fork+0x2d/0x50 > ? kthread_complete_and_exit+0x20/0x20 > ret_from_fork_asm+0x11/0x20 > > __schedule+0x48e/0xed0 > schedule+0x5a/0xc0 > blk_mq_freeze_queue_wait+0x62/0x90 > ? destroy_sched_domains_rcu+0x30/0x30 > blk_mq_exit_queue+0x151/0x180 > disk_release+0xe3/0xf0 > device_release+0x31/0x90 > kobject_put+0x6d/0x180 > nvme_scan_ns+0x858/0xc90 [nvme_core] > ? nvme_scan_work+0x281/0x560 [nvme_core] > nvme_scan_work+0x281/0x560 [nvme_core] > process_one_work+0x133/0x2f0 > ? mod_delayed_work_on+0x90/0x90 > worker_thread+0x2ec/0x400 > ? mod_delayed_work_on+0x90/0x90 > kthread+0xe2/0x110 > ? kthread_complete_and_exit+0x20/0x20 > ret_from_fork+0x2d/0x50 > ? kthread_complete_and_exit+0x20/0x20 > ret_from_fork_asm+0x11/0x20 It is one AB-BA deadlock, lockdep should have complained it, but nvme doesn't support owned freeze queue. Maybe the following change can avoid it? diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index c916176bd9f0..9967c4a7e72d 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -3004,6 +3004,7 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown) bool dead; mutex_lock(&dev->shutdown_lock); + nvme_quiesce_io_queues(&dev->ctrl); dead = nvme_pci_ctrl_is_dead(dev); if (state == NVME_CTRL_LIVE || state == NVME_CTRL_RESETTING) { if (pci_is_enabled(pdev)) @@ -3016,8 +3017,6 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown) nvme_wait_freeze_timeout(&dev->ctrl, NVME_IO_TIMEOUT); } - nvme_quiesce_io_queues(&dev->ctrl); - if (!dead && dev->ctrl.queue_count > 0) { nvme_delete_io_queues(dev); nvme_disable_ctrl(&dev->ctrl, shutdown); Thanks, Ming