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=-11.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7F89CC4338F for ; Wed, 11 Aug 2021 23:38:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F72E6104F for ; Wed, 11 Aug 2021 23:38:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232876AbhHKXjT (ORCPT ); Wed, 11 Aug 2021 19:39:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232827AbhHKXjS (ORCPT ); Wed, 11 Aug 2021 19:39:18 -0400 Received: from mail-qv1-xf2c.google.com (mail-qv1-xf2c.google.com [IPv6:2607:f8b0:4864:20::f2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DF27C061765 for ; Wed, 11 Aug 2021 16:38:54 -0700 (PDT) Received: by mail-qv1-xf2c.google.com with SMTP id m12so2146844qvt.1 for ; Wed, 11 Aug 2021 16:38:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=W8UXNm/aO0w65kk7gKAq65GEnTJuz2IPEoAIBva1F9w=; b=UsAyEyM9j3sVtm+024bJMNDSDVez/xAiAXE52MqK1HXwebgdqHBwrxaaROjmnrCmSw Bdn1WK2tVeMX4JpnbATPVMliP7uSe4F3dnLFqNrnwB5WS+cVYVjb+E31eqyLLHhjC/57 5Ire+pCUtrp/BtUOcahNZjlB897RDfsMKZpF0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=W8UXNm/aO0w65kk7gKAq65GEnTJuz2IPEoAIBva1F9w=; b=XDkMi/tS8NlX05NlfpRSKnGebedQboZWjmJjowk4v3T8kemISORsgWzgzIN/axdzJa QPkw1gG+5sFjATVEe3Pbf3Q0a47BOo7nL8qCYhFVhYTtQqtfMdq0iHt9Sjz90tZ9ALBN EDJG4USrtcQ1S1qdgNHWVv60kDQ29O+0RaEXrjum0ZrhWNI47tcnXspOZTQRjeMnwXUz sv8VSdc/TNBGeoiySXJgGClQUYchmBjSXsr0X2F/GjlmALgbKHtRAaRCLuz53xIJLY7h yRD/PsWF9f7ZMDv+oKlrCiMz602WjC0nRZgGaKid2a2z8Qj/LEBBx8k9efZjIauPIX0F rURw== X-Gm-Message-State: AOAM531ksJp+AV4py93S5AIis5ggTnq/moCU+DooSBn/1F6dCyqjNQY6 lbvzKazrqOmu0l++WWNmm4Lbl2KbSeuTPyf6ULLJOQ== X-Google-Smtp-Source: ABdhPJxZXzkAHP+ycjJA1pep3dmWHtK16U6A7LP+ft/nD4PHSDbuV1vCzcCWWzds4fwDE1VqOgYQA0unsSyi+QWsD1o= X-Received: by 2002:a0c:d801:: with SMTP id h1mr1244407qvj.60.1628725133226; Wed, 11 Aug 2021 16:38:53 -0700 (PDT) MIME-Version: 1.0 References: <20210811213749.3276687-1-kuba@kernel.org> <20210811213749.3276687-4-kuba@kernel.org> <20210811154441.3b593d94@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210811161658.64551a1c@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: <20210811161658.64551a1c@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Michael Chan Date: Wed, 11 Aug 2021 16:38:42 -0700 Message-ID: Subject: Re: [PATCH net v2 3/4] bnxt: make sure xmit_more + errors does not miss doorbells To: Jakub Kicinski Cc: David Miller , Jeffrey Huang , Eddie Wai , Prashant Sreedharan , Andrew Gospodarek , Netdev , Edwin Peer Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="0000000000000669cb05c9511f78" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --0000000000000669cb05c9511f78 Content-Type: text/plain; charset="UTF-8" On Wed, Aug 11, 2021 at 4:17 PM Jakub Kicinski wrote: > > On Wed, 11 Aug 2021 16:00:52 -0700 Michael Chan wrote: > > On Wed, Aug 11, 2021 at 3:44 PM Jakub Kicinski wrote: > > > On Wed, 11 Aug 2021 15:36:34 -0700 Michael Chan wrote: > > > > On Wed, Aug 11, 2021 at 2:38 PM Jakub Kicinski wrote: > > > > > @@ -367,6 +368,13 @@ static u16 bnxt_xmit_get_cfa_action(struct sk_buff *skb) > > > > > return md_dst->u.port_info.port_id; > > > > > } > > > > > > > > > > +static void bnxt_txr_db_kick(struct bnxt *bp, struct bnxt_tx_ring_info *txr, > > > > > + u16 prod) > > > > > +{ > > > > > + bnxt_db_write(bp, &txr->tx_db, prod); > > > > > + txr->kick_pending = 0; > > > > > +} > > > > > + > > > > > static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) > > > > > { > > > > > struct bnxt *bp = netdev_priv(dev); > > > > > @@ -396,6 +404,8 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) > > > > > free_size = bnxt_tx_avail(bp, txr); > > > > > if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) { > > > > > netif_tx_stop_queue(txq); > > > > > + if (net_ratelimit() && txr->kick_pending) > > > > > + netif_warn(bp, tx_err, dev, "bnxt: ring busy!\n"); > > > > > > > > You forgot to remove this. > > > > > > I changed my mind. I added the && txr->kick_pending to the condition, > > > if there is a race and napi starts the queue unnecessarily the kick > > > can't be pending. > > > > I don't understand. The queue should be stopped if we have <= > > MAX_SKB_FRAGS + 1 descriptors left. If there is a race and the queue > > is awake, the first TX packet may slip through if > > skb_shinfo(skb)->nr_frags is small and we have enough descriptors for > > it. Let's say xmit_more is set for this packet and so kick is > > pending. The next packet may not fit anymore and it will hit this > > check here. > > But even if we slip past this check we can only do it once, the check > at the end of start_xmit() will see we have fewer slots than MAX_FRAGS > + 2, ring the doorbell and stop. Yeah, I think you're right. --0000000000000669cb05c9511f78 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIQbQYJKoZIhvcNAQcCoIIQXjCCEFoCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg gg3EMIIFDTCCA/WgAwIBAgIQeEqpED+lv77edQixNJMdADANBgkqhkiG9w0BAQsFADBMMSAwHgYD VQQLExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UE AxMKR2xvYmFsU2lnbjAeFw0yMDA5MTYwMDAwMDBaFw0yODA5MTYwMDAwMDBaMFsxCzAJBgNVBAYT AkJFMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMTEwLwYDVQQDEyhHbG9iYWxTaWduIEdDQyBS MyBQZXJzb25hbFNpZ24gMiBDQSAyMDIwMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA vbCmXCcsbZ/a0fRIQMBxp4gJnnyeneFYpEtNydrZZ+GeKSMdHiDgXD1UnRSIudKo+moQ6YlCOu4t rVWO/EiXfYnK7zeop26ry1RpKtogB7/O115zultAz64ydQYLe+a1e/czkALg3sgTcOOcFZTXk38e aqsXsipoX1vsNurqPtnC27TWsA7pk4uKXscFjkeUE8JZu9BDKaswZygxBOPBQBwrA5+20Wxlk6k1 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