From patchwork Wed Jul 12 19:16:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13310839 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BA396EB64DA for ; Wed, 12 Jul 2023 19:17:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qJfKJ-0005md-7s; Wed, 12 Jul 2023 15:16:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qJfKH-0005mF-Nu for qemu-devel@nongnu.org; Wed, 12 Jul 2023 15:16:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qJfKG-0001wW-9K for qemu-devel@nongnu.org; Wed, 12 Jul 2023 15:16:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689189394; 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: content-transfer-encoding:content-transfer-encoding; bh=dsryfDy6LjagDRiliXIP3B2Rbyb/hrR3RC0ewdhj+4c=; b=TZwT0bFtNULrz/Qq1Z45WZPb6IPqGj+6FuwsuF+bQ8vmYJdO3FxFAa1O339IXTICwxftQ9 8taZ4WQ5qoKmNB9joeli7JDNpfuzbYHm2ztoOXmmitpfDUCoNa7dpKG7xz60gioGE7gr6f FJKGg4037tR76L6FJQAR+cNY2wPPfPs= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-117-FfPUmKHQOpCOsikadt37pQ-1; Wed, 12 Jul 2023 15:16:31 -0400 X-MC-Unique: FfPUmKHQOpCOsikadt37pQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 00802185A7A8; Wed, 12 Jul 2023 19:16:31 +0000 (UTC) Received: from localhost (unknown [10.39.192.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 153C2C1ED96; Wed, 12 Jul 2023 19:16:29 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Hanna Reitz , Stefan Hajnoczi , qemu-block@nongnu.org, Kevin Wolf , =?utf-8?q?Philippe_Ma?= =?utf-8?q?thieu-Daud=C3=A9?= , Fam Zheng , =?utf-8?b?THVrw6HFoSBEb2t0b3I=?= Subject: [PATCH] block/nvme: invoke blk_io_plug_call() outside q->lock Date: Wed, 12 Jul 2023 15:16:28 -0400 Message-Id: <20230712191628.252806-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org blk_io_plug_call() is invoked outside a blk_io_plug()/blk_io_unplug() section while opening the NVMe drive from: nvme_file_open() -> nvme_init() -> nvme_identify() -> nvme_admin_cmd_sync() -> nvme_submit_command() -> blk_io_plug_call() blk_io_plug_call() immediately invokes the given callback when the current thread is not plugged, as is the case during nvme_file_open(). Unfortunately, nvme_submit_command() calls blk_io_plug_call() with q->lock still held: ... q->sq.tail = (q->sq.tail + 1) % NVME_QUEUE_SIZE; q->need_kick++; blk_io_plug_call(nvme_unplug_fn, q); qemu_mutex_unlock(&q->lock); ^^^^^^^^^^^^^^^^^^^^^^^^^^^ nvme_unplug_fn() deadlocks trying to acquire q->lock because the lock is already acquired by the same thread. The symptom is that QEMU hangs during startup while opening the NVMe drive. Fix this by moving the blk_io_plug_call() outside q->lock. This is safe because no other thread runs code related to this queue and blk_io_plug_call()'s internal state is immune to thread safety issues since it is thread-local. Reported-by: Lukáš Doktor Fixes: f2e590002bd6 ("block/nvme: convert to blk_io_plug_call() API") Signed-off-by: Stefan Hajnoczi Tested-by: Lukas Doktor --- block/nvme.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/nvme.c b/block/nvme.c index 7ca85bc44a..b6e95f0b7e 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -501,8 +501,9 @@ static void nvme_submit_command(NVMeQueuePair *q, NVMeRequest *req, q->sq.tail * NVME_SQ_ENTRY_BYTES, cmd, sizeof(*cmd)); q->sq.tail = (q->sq.tail + 1) % NVME_QUEUE_SIZE; q->need_kick++; + qemu_mutex_unlock(&q->lock); + blk_io_plug_call(nvme_unplug_fn, q); - qemu_mutex_unlock(&q->lock); } static void nvme_admin_cmd_sync_cb(void *opaque, int ret)