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 8578CC468C6 for ; Thu, 19 Jul 2018 07:48:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BAAF20671 for ; Thu, 19 Jul 2018 07:48:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BAAF20671 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 S1731431AbeGSIao (ORCPT ); Thu, 19 Jul 2018 04:30:44 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:34339 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727700AbeGSIao (ORCPT ); Thu, 19 Jul 2018 04:30:44 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 44E96491580D7; Thu, 19 Jul 2018 15:48:45 +0800 (CST) Received: from [10.177.253.249] (10.177.253.249) by smtp.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.382.0; Thu, 19 Jul 2018 15:48:39 +0800 Subject: Re: [V9fs-developer] [PATCH v3] Fix a hard lockup case in the virtio transport To: jiangyiwen , Andrew Morton , Eric Van Hensbergen , "Ron Minnich" , Latchesar Ionkov References: <5B503AEC.5080404@huawei.com> CC: , Linux Kernel Mailing List From: piaojun Message-ID: <5B504231.3090706@huawei.com> Date: Thu, 19 Jul 2018 15:48:01 +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: <5B503AEC.5080404@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 2018/7/19 15:17, 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 | 21 +++++++++++---------- > 1 file changed, 11 insertions(+), 10 deletions(-) > > diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c > index 05006cb..3589864 100644 > --- a/net/9p/trans_virtio.c > +++ b/net/9p/trans_virtio.c > @@ -144,24 +144,25 @@ static void req_done(struct virtqueue *vq) > struct virtio_chan *chan = vq->vdev->priv; > unsigned int len; > struct p9_req_t *req; > + bool need_wakeup = false; > unsigned long flags; > > 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; > + spin_lock_irqsave(&chan->lock, flags); > + while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) { > + if (!chan->ring_bufs_avail) { > + chan->ring_bufs_avail = 1; > + need_wakeup = true; > } > - 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); > + /* Wakeup if anyone waiting for VirtIO ring space. */ > + if (need_wakeup) > + wake_up(chan->vc_wq); > } > > /** >