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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 89C97C433B4 for ; Tue, 13 Apr 2021 14:03:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 718CE613B2 for ; Tue, 13 Apr 2021 14:03:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346224AbhDMODe (ORCPT ); Tue, 13 Apr 2021 10:03:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24696 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346218AbhDMODX (ORCPT ); Tue, 13 Apr 2021 10:03:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618322583; 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: in-reply-to:in-reply-to:references:references; bh=swYl2fUsBiiVjxnatT+LNRdbKdi4oKKSZ6QxSoSZPJk=; b=hoi/sux8OpWlEBGSsTuaLILxNVectkWGH5rwrm3MPTSzwDTv2rTNK3r/bq74r/cL7mpG6e DpFaC/Oaexh4j37ygu8Gld7ok8f0oEJUO+u0BEiMNLCUpUJ2qhcSbkNeviYCV39zT6tEp3 JblT0stoivs1crufMty4jKyAy+m1BEU= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-450-UvXmZ7JUPvSc-Nte9obcJw-1; Tue, 13 Apr 2021 10:03:01 -0400 X-MC-Unique: UvXmZ7JUPvSc-Nte9obcJw-1 Received: by mail-wr1-f72.google.com with SMTP id z6so810946wrh.11 for ; Tue, 13 Apr 2021 07:03:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=swYl2fUsBiiVjxnatT+LNRdbKdi4oKKSZ6QxSoSZPJk=; b=VTxcwSCNGvuXdGDSK/4GXrGc/BxroJ5VuT001FmMc2j4cfVgS5nw2EZ4XFdRCO4YsB JxxXtPNHSLhxeIEbrIukUNO5g7d71D8tIW4rzzqDdHm8UjqxcT/w90DIx3Da44RLHist /qjuI2eo48d8hJOAkM/eyaxUOZ5EqJPs1R6Qt+mo0MM9s9RNE+i6vd2VxzojjfhgaElA lKmXYi2dUO/Q0jgTeQ/GI7/pxWKCgYkX4mDaMGPqpcm1U2bNQBQqduQkNooJvYj+R6O7 H7o2IJl+aErLQevd5Z1xNs70pkgYy3STGNJy6E3oqUgekYSFt2g4V2qcvBm9+Sh2riac YaOg== X-Gm-Message-State: AOAM5317RPZpx+PFwAG6HriiTt5PGY/F3zMUBJ2pOFdEbDvgkriw3mLZ rU3ZcPS6+iw3jAdya86QuIgp5/eGdGEtxVqnEr561KKu8scEzUsJo4rMapwA0OOlGIeDIxwt+jg UuJdnt66bJ0j+Z3ehi5egiEcz X-Received: by 2002:a05:600c:2312:: with SMTP id 18mr188040wmo.68.1618322579650; Tue, 13 Apr 2021 07:02:59 -0700 (PDT) X-Google-Smtp-Source: ABdhPJytEpDKGiR9o7JztK9xr/CiCIDyo4VVVhCw7mpf/3UO/HzypD1HWJ5i0ZPENNve3YfdPorFWg== X-Received: by 2002:a05:600c:2312:: with SMTP id 18mr188006wmo.68.1618322579419; Tue, 13 Apr 2021 07:02:59 -0700 (PDT) Received: from redhat.com ([2a10:8006:2281:0:1994:c627:9eac:1825]) by smtp.gmail.com with ESMTPSA id q20sm2867997wmq.2.2021.04.13.07.02.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Apr 2021 07:02:58 -0700 (PDT) Date: Tue, 13 Apr 2021 10:02:55 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, Jakub Kicinski , Wei Wang , David Miller , netdev@vger.kernel.org, Willem de Bruijn , virtualization@lists.linux-foundation.org Subject: Re: [PATCH RFC v2 3/4] virtio_net: move tx vq operation under tx queue lock Message-ID: <20210413100222-mutt-send-email-mst@kernel.org> References: <20210413054733.36363-1-mst@redhat.com> <20210413054733.36363-4-mst@redhat.com> <805053bf-960f-3c34-ce23-012d121ca937@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <805053bf-960f-3c34-ce23-012d121ca937@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 13, 2021 at 04:54:42PM +0800, Jason Wang wrote: > > 在 2021/4/13 下午1:47, Michael S. Tsirkin 写道: > > It's unsafe to operate a vq from multiple threads. > > Unfortunately this is exactly what we do when invoking > > clean tx poll from rx napi. > > As a fix move everything that deals with the vq to under tx lock. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > drivers/net/virtio_net.c | 22 +++++++++++++++++++++- > > 1 file changed, 21 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > index 16d5abed582c..460ccdbb840e 100644 > > --- a/drivers/net/virtio_net.c > > +++ b/drivers/net/virtio_net.c > > @@ -1505,6 +1505,8 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) > > struct virtnet_info *vi = sq->vq->vdev->priv; > > unsigned int index = vq2txq(sq->vq); > > struct netdev_queue *txq; > > + int opaque; > > + bool done; > > if (unlikely(is_xdp_raw_buffer_queue(vi, index))) { > > /* We don't need to enable cb for XDP */ > > @@ -1514,10 +1516,28 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) > > txq = netdev_get_tx_queue(vi->dev, index); > > __netif_tx_lock(txq, raw_smp_processor_id()); > > + virtqueue_disable_cb(sq->vq); > > free_old_xmit_skbs(sq, true); > > + > > + opaque = virtqueue_enable_cb_prepare(sq->vq); > > + > > + done = napi_complete_done(napi, 0); > > + > > + if (!done) > > + virtqueue_disable_cb(sq->vq); > > + > > __netif_tx_unlock(txq); > > - virtqueue_napi_complete(napi, sq->vq, 0); > > > So I wonder why not simply move __netif_tx_unlock() after > virtqueue_napi_complete()? > > Thanks > Because that calls tx poll which also takes tx lock internally ... > > + if (done) { > > + if (unlikely(virtqueue_poll(sq->vq, opaque))) { > > + if (napi_schedule_prep(napi)) { > > + __netif_tx_lock(txq, raw_smp_processor_id()); > > + virtqueue_disable_cb(sq->vq); > > + __netif_tx_unlock(txq); > > + __napi_schedule(napi); > > + } > > + } > > + } > > if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > > netif_tx_wake_queue(txq);