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Tsirkin" To: Jason Wang 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 In-Reply-To: <805053bf-960f-3c34-ce23-012d121ca937@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Willem de Bruijn , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Jakub Kicinski , Wei Wang , David Miller X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" T24gVHVlLCBBcHIgMTMsIDIwMjEgYXQgMDQ6NTQ6NDJQTSArMDgwMCwgSmFzb24gV2FuZyB3cm90 ZToKPiAKPiDlnKggMjAyMS80LzEzIOS4i+WNiDE6NDcsIE1pY2hhZWwgUy4gVHNpcmtpbiDlhpnp gZM6Cj4gPiBJdCdzIHVuc2FmZSB0byBvcGVyYXRlIGEgdnEgZnJvbSBtdWx0aXBsZSB0aHJlYWRz Lgo+ID4gVW5mb3J0dW5hdGVseSB0aGlzIGlzIGV4YWN0bHkgd2hhdCB3ZSBkbyB3aGVuIGludm9r aW5nCj4gPiBjbGVhbiB0eCBwb2xsIGZyb20gcnggbmFwaS4KPiA+IEFzIGEgZml4IG1vdmUgZXZl cnl0aGluZyB0aGF0IGRlYWxzIHdpdGggdGhlIHZxIHRvIHVuZGVyIHR4IGxvY2suCj4gPiAKPiA+ IFNpZ25lZC1vZmYtYnk6IE1pY2hhZWwgUy4gVHNpcmtpbiA8bXN0QHJlZGhhdC5jb20+Cj4gPiAt LS0KPiA+ICAgZHJpdmVycy9uZXQvdmlydGlvX25ldC5jIHwgMjIgKysrKysrKysrKysrKysrKysr KysrLQo+ID4gICAxIGZpbGUgY2hhbmdlZCwgMjEgaW5zZXJ0aW9ucygrKSwgMSBkZWxldGlvbigt KQo+ID4gCj4gPiBkaWZmIC0tZ2l0IGEvZHJpdmVycy9uZXQvdmlydGlvX25ldC5jIGIvZHJpdmVy cy9uZXQvdmlydGlvX25ldC5jCj4gPiBpbmRleCAxNmQ1YWJlZDU4MmMuLjQ2MGNjZGJiODQwZSAx MDA2NDQKPiA+IC0tLSBhL2RyaXZlcnMvbmV0L3ZpcnRpb19uZXQuYwo+ID4gKysrIGIvZHJpdmVy cy9uZXQvdmlydGlvX25ldC5jCj4gPiBAQCAtMTUwNSw2ICsxNTA1LDggQEAgc3RhdGljIGludCB2 aXJ0bmV0X3BvbGxfdHgoc3RydWN0IG5hcGlfc3RydWN0ICpuYXBpLCBpbnQgYnVkZ2V0KQo+ID4g ICAJc3RydWN0IHZpcnRuZXRfaW5mbyAqdmkgPSBzcS0+dnEtPnZkZXYtPnByaXY7Cj4gPiAgIAl1 bnNpZ25lZCBpbnQgaW5kZXggPSB2cTJ0eHEoc3EtPnZxKTsKPiA+ICAgCXN0cnVjdCBuZXRkZXZf cXVldWUgKnR4cTsKPiA+ICsJaW50IG9wYXF1ZTsKPiA+ICsJYm9vbCBkb25lOwo+ID4gICAJaWYg KHVubGlrZWx5KGlzX3hkcF9yYXdfYnVmZmVyX3F1ZXVlKHZpLCBpbmRleCkpKSB7Cj4gPiAgIAkJ LyogV2UgZG9uJ3QgbmVlZCB0byBlbmFibGUgY2IgZm9yIFhEUCAqLwo+ID4gQEAgLTE1MTQsMTAg KzE1MTYsMjggQEAgc3RhdGljIGludCB2aXJ0bmV0X3BvbGxfdHgoc3RydWN0IG5hcGlfc3RydWN0 ICpuYXBpLCBpbnQgYnVkZ2V0KQo+ID4gICAJdHhxID0gbmV0ZGV2X2dldF90eF9xdWV1ZSh2aS0+ ZGV2LCBpbmRleCk7Cj4gPiAgIAlfX25ldGlmX3R4X2xvY2sodHhxLCByYXdfc21wX3Byb2Nlc3Nv cl9pZCgpKTsKPiA+ICsJdmlydHF1ZXVlX2Rpc2FibGVfY2Ioc3EtPnZxKTsKPiA+ICAgCWZyZWVf b2xkX3htaXRfc2ticyhzcSwgdHJ1ZSk7Cj4gPiArCj4gPiArCW9wYXF1ZSA9IHZpcnRxdWV1ZV9l bmFibGVfY2JfcHJlcGFyZShzcS0+dnEpOwo+ID4gKwo+ID4gKwlkb25lID0gbmFwaV9jb21wbGV0 ZV9kb25lKG5hcGksIDApOwo+ID4gKwo+ID4gKwlpZiAoIWRvbmUpCj4gPiArCQl2aXJ0cXVldWVf ZGlzYWJsZV9jYihzcS0+dnEpOwo+ID4gKwo+ID4gICAJX19uZXRpZl90eF91bmxvY2sodHhxKTsK PiA+IC0JdmlydHF1ZXVlX25hcGlfY29tcGxldGUobmFwaSwgc3EtPnZxLCAwKTsKPiAKPiAKPiBT byBJIHdvbmRlciB3aHkgbm90IHNpbXBseSBtb3ZlIF9fbmV0aWZfdHhfdW5sb2NrKCkgYWZ0ZXIK PiB2aXJ0cXVldWVfbmFwaV9jb21wbGV0ZSgpPwo+IAo+IFRoYW5rcwo+IAoKCkJlY2F1c2UgdGhh dCBjYWxscyB0eCBwb2xsIHdoaWNoIGFsc28gdGFrZXMgdHggbG9jayBpbnRlcm5hbGx5IC4uLgoK Cj4gPiArCWlmIChkb25lKSB7Cj4gPiArCQlpZiAodW5saWtlbHkodmlydHF1ZXVlX3BvbGwoc3Et PnZxLCBvcGFxdWUpKSkgewo+ID4gKwkJCWlmIChuYXBpX3NjaGVkdWxlX3ByZXAobmFwaSkpIHsK PiA+ICsJCQkJX19uZXRpZl90eF9sb2NrKHR4cSwgcmF3X3NtcF9wcm9jZXNzb3JfaWQoKSk7Cj4g PiArCQkJCXZpcnRxdWV1ZV9kaXNhYmxlX2NiKHNxLT52cSk7Cj4gPiArCQkJCV9fbmV0aWZfdHhf dW5sb2NrKHR4cSk7Cj4gPiArCQkJCV9fbmFwaV9zY2hlZHVsZShuYXBpKTsKPiA+ICsJCQl9Cj4g PiArCQl9Cj4gPiArCX0KPiA+ICAgCWlmIChzcS0+dnEtPm51bV9mcmVlID49IDIgKyBNQVhfU0tC X0ZSQUdTKQo+ID4gICAJCW5ldGlmX3R4X3dha2VfcXVldWUodHhxKTsKCl9fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClZpcnR1YWxpemF0aW9uIG1haWxpbmcg bGlzdApWaXJ0dWFsaXphdGlvbkBsaXN0cy5saW51eC1mb3VuZGF0aW9uLm9yZwpodHRwczovL2xp c3RzLmxpbnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby92aXJ0dWFsaXphdGlvbg== 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 ; 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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);