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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 34C59C49EA5 for ; Thu, 24 Jun 2021 16:14:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1762F61375 for ; Thu, 24 Jun 2021 16:14:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231621AbhFXQQW (ORCPT ); Thu, 24 Jun 2021 12:16:22 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:46620 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230040AbhFXQQQ (ORCPT ); Thu, 24 Jun 2021 12:16:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624551236; 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=cOyh19f+n3Klc9n0Uf50USUZ/OAvnTAcZiRzl4mD+JA=; b=QaAx30BLq9Xssu3dc4tRGB973dg9f2LXLDQ4OizivXQLvyFdPc+SHQqwvB01xWAiQxuARQ OS/VzA3jhKRpw0+na41G5nP9huDZlFU2YReb0imClaw8jRSU6BLSmoQWfqvjvvp4ZnxXKj WXLepa65qi1SYJaVy0y4KhSa0jyPI+0= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-442-4zRlfLC3PeW9gYPisz1ARw-1; Thu, 24 Jun 2021 12:13:55 -0400 X-MC-Unique: 4zRlfLC3PeW9gYPisz1ARw-1 Received: by mail-ej1-f69.google.com with SMTP id lt4-20020a170906fa84b0290481535542e3so2199450ejb.18 for ; Thu, 24 Jun 2021 09:13:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cOyh19f+n3Klc9n0Uf50USUZ/OAvnTAcZiRzl4mD+JA=; b=FZTA7Bxr/IaFtjdoKOSt+ekoMTk9bu+aM+LnBSUrmEmv8FOwg9oM3Zb/yAYyMwWSLn FJg85i2fBP4P+QAMdEbqS62CfrMUYXfszrriL2K5KvWZvFvjnmwPqlNicGS/JQBUw9LK 7tfNXndvoRtbv9CplPwNTLKWha++W33YQf1CUv44z8QKlmWNvQ/RPN/wS72M37ISSpsL 7uEP+swyXmZRpXVEJSrmuSGdQFRqRAsM0U3Th4wCj/GRWxhEAtHGUbNHGFAWVruoxyga MA1PuwXupPs43zoPnX6M661Oq4mpqBHTuChjHAQmYnOcB2Elxmsoi5rTegumvRxqVUUx MHJg== X-Gm-Message-State: AOAM533pH5UM3P1uU0asl+rOWSt72qe9g08wLC3Bw/z9FlnJauJEpdsp ULeI7IWPUQngqpRx0AYaw9oTw4LaZZAZAYhs/D+E1pT5NVXVa3k0KpPja+b35sSBf2zcoliEKTa tXSd5QnIFeUBNKy3I X-Received: by 2002:aa7:dc0d:: with SMTP id b13mr8086192edu.288.1624551234002; Thu, 24 Jun 2021 09:13:54 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwO83p9KKeIz6WYXSUxDTv54YrbHmZN8vEVgN4NSgGIUd/3XQocFyAZ4VFu9V7EzZ2au7ZN8g== X-Received: by 2002:aa7:dc0d:: with SMTP id b13mr8086172edu.288.1624551233868; Thu, 24 Jun 2021 09:13:53 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id d2sm1433158ejo.13.2021.06.24.09.13.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Jun 2021 09:13:51 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id AC1B8180741; Thu, 24 Jun 2021 18:06:10 +0200 (CEST) From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: Martin KaFai Lau , Hangbin Liu , Jesper Dangaard Brouer , Magnus Karlsson , "Paul E . McKenney" , Jakub Kicinski , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Edward Cree , Martin Habets Subject: [PATCH bpf-next v5 16/19] sfc: remove rcu_read_lock() around XDP program invocation Date: Thu, 24 Jun 2021 18:06:06 +0200 Message-Id: <20210624160609.292325-17-toke@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210624160609.292325-1-toke@redhat.com> References: <20210624160609.292325-1-toke@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The sfc driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. This turns out to be harmless because it all happens in a single NAPI poll cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock() misleading. Rather than extend the scope of the rcu_read_lock(), just get rid of it entirely. With the addition of RCU annotations to the XDP_REDIRECT map types that take bh execution into account, lockdep even understands this to be safe, so there's really no reason to keep it around. Cc: Edward Cree Cc: Martin Habets Acked-by: Edward Cree Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/sfc/rx.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c index 17b8119c48e5..606750938b89 100644 --- a/drivers/net/ethernet/sfc/rx.c +++ b/drivers/net/ethernet/sfc/rx.c @@ -260,18 +260,14 @@ static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel, s16 offset; int err; - rcu_read_lock(); - xdp_prog = rcu_dereference(efx->xdp_prog); - if (!xdp_prog) { - rcu_read_unlock(); + xdp_prog = rcu_dereference_bh(efx->xdp_prog); + if (!xdp_prog) return true; - } rx_queue = efx_channel_get_rx_queue(channel); if (unlikely(channel->rx_pkt_n_frags > 1)) { /* We can't do XDP on fragmented packets - drop. */ - rcu_read_unlock(); efx_free_rx_buffers(rx_queue, rx_buf, channel->rx_pkt_n_frags); if (net_ratelimit()) @@ -296,7 +292,6 @@ static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel, rx_buf->len, false); xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp); - rcu_read_unlock(); offset = (u8 *)xdp.data - *ehp; -- 2.32.0