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=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 AAE36C4CEC9 for ; Tue, 17 Sep 2019 23:45:54 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6EEE42054F for ; Tue, 17 Sep 2019 23:45:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HOyGQ4WA"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="j++T2+zn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6EEE42054F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=RX4zjosWRLciQAVr71LVohFpHiyOT8VoKhaB/j0QNkk=; b=HOyGQ4WAM09yNO kKZk0XDF3CBhS7SoLr9NdFGN4NLlPOO1jO0wwYvLBRvPQmbpBOvhKfHvOqFnZ3BAme5Q6gx0b+6R9 s3Hxvwhgna6wsdhmYNETboSqiL6KR61uE+NC0kIkyoTWw9AA4EYkn6cmau0M8nmuXoR3ccKK17dVg oMK6ElLCxnViFaow0UBKo9KeovlN4pzZmsKVdo0Qfr8c5m5DIBjxIwQGowRZZ4JdUHa5EJ8TBoVXk /uhL5BJhqCImD1Frd4jIXHY841+C/Hl4MJNdOV8MOEkMnRR0X4w0Gd2zW25S3WTit+VFZ33giksGB ZnpqsGssH4R6rLXNKKfg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iANAA-0002Hg-Rc; Tue, 17 Sep 2019 23:45:38 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iANA7-0002HK-Lk for linux-nvme@lists.infradead.org; Tue, 17 Sep 2019 23:45:37 +0000 Received: from keith-busch (unknown [8.36.226.102]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C18A2206C2; Tue, 17 Sep 2019 23:45:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568763935; bh=+hz8kISpaGmrCv5P1SzuxdB0GQ6swEzsB5aXsXjoGPU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j++T2+znHpZEoefuwJFqX8aasgvxAWpa9IdkgrUn3bqyd2JSxmBph2G9JvczTXAvh 9wk0XvU/TQdK6uDIgU5Wb91OLtLYbS6HZHiEmywnA/i8KLjnqcC9H9C7vWggsyKnf0 8p7M9S6WKLG8ARtLU1Hga5Z606FBd9IJtekk8mXc= Date: Tue, 17 Sep 2019 17:45:33 -0600 From: Keith Busch To: Balbir Singh Subject: Re: [PATCH v3 1/2] nvme/host/pci: Fix a race in controller removal Message-ID: <20190917234531.GA17026@keith-busch> References: <20190917224105.6758-1-sblbir@amzn.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190917224105.6758-1-sblbir@amzn.com> User-Agent: Mutt/1.9.1 (2017-09-22) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190917_164535_751505_65521CC5 X-CRM114-Status: GOOD ( 23.97 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: axboe@fb.com, hch@lst.de, linux-nvme@lists.infradead.org, sagi@grimberg.me Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Sep 17, 2019 at 10:41:04PM +0000, Balbir Singh wrote: > This race is hard to hit in general, now that we > have the shutdown_lock in both nvme_reset_work() and > nvme_dev_disable() > > The real issue is that after doing all the setup work > in nvme_reset_work(), when get another timeout (nvme_timeout()), > then we proceed to disable the controller. This causes > the reset work to only partially progress and then fail. > > Depending on the progress made, we call into > nvme_remove_dead_ctrl(), which does another > nvme_dev_disable() freezing the block-mq queues. > > I've noticed a race with udevd with udevd trying to re-read > the partition table, it ends up with the bd_mutex held and > it ends up waiting in blk_queue_enter(), since we froze > the queues in nvme_dev_disable(). nvme_kill_queues() calls > revalidate_disk() and ends up waiting on the bd_mutex > resulting in a deadlock. > > Allow the hung tasks a chance by unfreezing the queues after > setting dying bits on the queue, then call revalidate_disk() > to update the disk size. > > NOTE: I've seen this race when the controller does not > respond to IOs or abort requests, but responds to other > commands and even signals it's ready after its reset, > but still drops IO. I've tested this by emulating the > behaviour in the driver. I recommend the following changelog for this commit: User space programs like udevd may try to read to partitions at the same time the driver detects a namespace is unusable, and may deadlock if revalidate_disk() is called while such a process is waiting to enter the frozen queue. On detecting a dead namespace, move the disk revalidate after unblocking dispatchers that may be holding bd_butex. And that's it. > Signed-off-by: Balbir Singh > --- > > Changelog v3 > 1. Simplify the comment about moving revalidate_disk > Changelog v2 > 1. Rely on blk_set_queue_dying to do the wake_all() > > drivers/nvme/host/core.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > index b45f82d58be8..6ad1f1df9e44 100644 > --- a/drivers/nvme/host/core.c > +++ b/drivers/nvme/host/core.c > @@ -103,10 +103,13 @@ static void nvme_set_queue_dying(struct nvme_ns *ns) > */ > if (!ns->disk || test_and_set_bit(NVME_NS_DEAD, &ns->flags)) > return; > - revalidate_disk(ns->disk); > blk_set_queue_dying(ns->queue); > /* Forcibly unquiesce queues to avoid blocking dispatch */ > blk_mq_unquiesce_queue(ns->queue); > + /* > + * Revalidate after unblocking dispatchers that may be holding bd_butex > + */ > + revalidate_disk(ns->disk); > } > > static void nvme_queue_scan(struct nvme_ctrl *ctrl) > -- > 2.16.5 > _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme