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 4E519ECDFB1 for ; Tue, 17 Jul 2018 11:35:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F16DB20C09 for ; Tue, 17 Jul 2018 11:35:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F16DB20C09 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 S1731114AbeGQMHW (ORCPT ); Tue, 17 Jul 2018 08:07:22 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:58489 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730444AbeGQMHW (ORCPT ); Tue, 17 Jul 2018 08:07:22 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 33AB22825C4A1; Tue, 17 Jul 2018 19:35:06 +0800 (CST) Received: from [10.177.253.249] (10.177.253.249) by smtp.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.382.0; Tue, 17 Jul 2018 19:34:58 +0800 Subject: Re: [V9fs-developer] [PATCH v2] net/9p: Fix a deadlock case in the virtio transport To: jiangyiwen , Andrew Morton , Eric Van Hensbergen , "Ron Minnich" , Latchesar Ionkov References: <5B4DCD0A.8040600@huawei.com> CC: , Linux Kernel Mailing List From: piaojun Message-ID: <5B4DD46D.4060801@huawei.com> Date: Tue, 17 Jul 2018 19:35:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <5B4DCD0A.8040600@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.253.249] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org LGTM On 2018/7/17 19:03, jiangyiwen wrote: > 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 Reviewed-by: Jun Piao > --- > net/9p/trans_virtio.c | 17 ++++++----------- > 1 file changed, 6 insertions(+), 11 deletions(-) > > diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c > index 05006cb..e5fea8b 100644 > --- a/net/9p/trans_virtio.c > +++ b/net/9p/trans_virtio.c > @@ -148,20 +148,15 @@ static void req_done(struct virtqueue *vq) > > p9_debug(P9_DEBUG_TRANS, ": request done\n"); > > - while (1) { > - spin_lock_irqsave(&chan->lock, flags); > - req = virtqueue_get_buf(chan->vq, &len); > - if (req == NULL) { > - spin_unlock_irqrestore(&chan->lock, flags); > - 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); > + spin_lock_irqsave(&chan->lock, flags); > + while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) { > if (len) > p9_client_cb(chan->client, req, REQ_STATUS_RCVD); > } > + chan->ring_bufs_avail = 1; > + spin_unlock_irqrestore(&chan->lock, flags); > + /* Wakeup if anyone waiting for VirtIO ring space. */ > + wake_up(chan->vc_wq); > } > > /** >