From patchwork Wed Jun 9 10:33:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= X-Patchwork-Id: 12309567 X-Patchwork-Delegate: bpf@iogearbox.net 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=-19.0 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, USER_AGENT_GIT 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 28293C48BE0 for ; Wed, 9 Jun 2021 10:33:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1350A61185 for ; Wed, 9 Jun 2021 10:33:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237132AbhFIKfv (ORCPT ); Wed, 9 Jun 2021 06:35:51 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:33146 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238903AbhFIKff (ORCPT ); Wed, 9 Jun 2021 06:35:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623234820; 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=b6/ywr8A84xw5GpjlyvV4hRNlzB/uVzXQRS5Ys9UtLc=; b=LYvg19KeOaNn1RUYY9IhTFgzuk1eW/+SXH/70Fd7ZcvvSs+foxl/Ijq33XrUDdMAFwADG2 iZR4MDQpNVVkzwIJP6B5k8CI3FPmt4eeRRIgGxF8jMPZZUpphXMMhDCZ7Eu8NR0TphqM4+ ZX1VnqQEmSS+RSfKxOMv2xMvfUmjEUU= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-234-Ms80x6hjPcS96zBoqFB1gA-1; Wed, 09 Jun 2021 06:33:39 -0400 X-MC-Unique: Ms80x6hjPcS96zBoqFB1gA-1 Received: by mail-ed1-f72.google.com with SMTP id dd28-20020a056402313cb029038fc9850034so12229698edb.7 for ; Wed, 09 Jun 2021 03:33:39 -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=b6/ywr8A84xw5GpjlyvV4hRNlzB/uVzXQRS5Ys9UtLc=; b=Yv7M9ECVbT3tvku0mmBz2yQCpoc3syrzxuXg+NsVsz1V9ROEJly3FFDiniZ70OqdCP F6xkpCvLO+BdWC9+1r48FoMxrtzs6Goy9WJt3lwv4emDHgtxN7rkq4EgAPfk43ddHj62 6vyd6Wicmm801UClN5pKp11zHU4Hlm+eQQq9gq3vRZyMyD4s8JeQLXYbe5mzjPp9K8fc ybj8kTdNPYJHOP8uRdPn5N0BxhPsfvaW8A4jFiXUIxhl8A25oTGR5NLtLWdNN6dc/Ygs PpkvDEX4LpIl1T8+uRFv6Lx/uMQp9NnsV+vsyhB2aNLEwd0Fcy7USeEEETTUxnue5T+4 LVVQ== X-Gm-Message-State: AOAM530HCZo1PMzNdmlpn5iM6IFBdYPu8sc3OobE3zbBTJfJYlr/aNTE ydtBg8nwZJHV5Ut3nDvJUOrW4A/DtAiRXoRLkPGe1Qzh3inoCHAgz5rSF42VKWGidEoj+nrVUNb vmBRGeMSZvY27 X-Received: by 2002:a05:6402:511:: with SMTP id m17mr29902728edv.1.1623234818393; Wed, 09 Jun 2021 03:33:38 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxy8dEQdT/+2mrdhhPDQI/OtNZSHMX52Tnhpuds9eoPNSLQsCBSfjSo0BHivEiX/iSeqUt4zA== X-Received: by 2002:a05:6402:511:: with SMTP id m17mr29902711edv.1.1623234818248; Wed, 09 Jun 2021 03:33:38 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id l8sm933170ejp.40.2021.06.09.03.33.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 03:33:36 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id F2934180734; Wed, 9 Jun 2021 12:33:30 +0200 (CEST) From: =?utf-8?q?Toke_H=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" , =?utf-8?q?Toke_H=C3=B8iland-J?= =?utf-8?q?=C3=B8rgensen?= , Giuseppe Cavallaro , Alexandre Torgue , Jose Abreu Subject: [PATCH bpf-next 16/17] stmmac: remove rcu_read_lock() around XDP program invocation Date: Wed, 9 Jun 2021 12:33:25 +0200 Message-Id: <20210609103326.278782-17-toke@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210609103326.278782-1-toke@redhat.com> References: <20210609103326.278782-1-toke@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The stmmac 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: Giuseppe Cavallaro Cc: Alexandre Torgue Cc: Jose Abreu Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index bf9fe25fed69..08c4b999e1ba 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -4654,7 +4654,6 @@ static int stmmac_xdp_xmit_back(struct stmmac_priv *priv, return res; } -/* This function assumes rcu_read_lock() is held by the caller. */ static int __stmmac_xdp_run_prog(struct stmmac_priv *priv, struct bpf_prog *prog, struct xdp_buff *xdp) @@ -4696,17 +4695,14 @@ static struct sk_buff *stmmac_xdp_run_prog(struct stmmac_priv *priv, struct bpf_prog *prog; int res; - rcu_read_lock(); - prog = READ_ONCE(priv->xdp_prog); if (!prog) { res = STMMAC_XDP_PASS; - goto unlock; + goto out; } res = __stmmac_xdp_run_prog(priv, prog, xdp); -unlock: - rcu_read_unlock(); +out: return ERR_PTR(-res); } @@ -4976,10 +4972,8 @@ static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue) buf->xdp->data_end = buf->xdp->data + buf1_len; xsk_buff_dma_sync_for_cpu(buf->xdp, rx_q->xsk_pool); - rcu_read_lock(); prog = READ_ONCE(priv->xdp_prog); res = __stmmac_xdp_run_prog(priv, prog, buf->xdp); - rcu_read_unlock(); switch (res) { case STMMAC_XDP_PASS: