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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 12624ECDFB0 for ; Sat, 14 Jul 2018 08:48:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C909F20837 for ; Sat, 14 Jul 2018 08:48:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C909F20837 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727411AbeGNJGx (ORCPT ); Sat, 14 Jul 2018 05:06:53 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:9238 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726657AbeGNJGx (ORCPT ); Sat, 14 Jul 2018 05:06:53 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 279BF5C629A0C; Sat, 14 Jul 2018 16:48:18 +0800 (CST) Received: from [127.0.0.1] (10.177.16.168) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.382.0; Sat, 14 Jul 2018 16:48:18 +0800 From: jiangyiwen Subject: [V9fs-developer] [PATCH] net/9p: Fix a deadlock case in the virtio transport To: Andrew Morton , Eric Van Hensbergen , Ron Minnich , Latchesar Ionkov CC: Linux Kernel Mailing List , , Dominique Martinet Message-ID: <5B49B8CF.40709@huawei.com> Date: Sat, 14 Jul 2018 16:48:15 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.16.168] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When client has multiple threads that issue io requests all the time, and the server has a very good performance, it may cause cpu is running in the irq context for a long time because it can check virtqueue has buf in the *while* loop. So we should keep chan->lock in the whole loop. Signed-off-by: Yiwen Jiang --- net/9p/trans_virtio.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 05006cb..9b0f5f2 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -148,20 +148,18 @@ static void req_done(struct virtqueue *vq) p9_debug(P9_DEBUG_TRANS, ": request done\n"); + spin_lock_irqsave(&chan->lock, flags); while (1) { - spin_lock_irqsave(&chan->lock, flags); req = virtqueue_get_buf(chan->vq, &len); - if (req == NULL) { - spin_unlock_irqrestore(&chan->lock, flags); + if (req == NULL) break; - } chan->ring_bufs_avail = 1; - spin_unlock_irqrestore(&chan->lock, flags); /* Wakeup if anyone waiting for VirtIO ring space. */ wake_up(chan->vc_wq); if (len) p9_client_cb(chan->client, req, REQ_STATUS_RCVD); } + spin_unlock_irqrestore(&chan->lock, flags); } /** -- 1.8.3.1