From patchwork Wed Jun 23 11:07:15 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: 466252 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=-19.1 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=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 26526C4743C for ; Wed, 23 Jun 2021 11:08:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11A6561003 for ; Wed, 23 Jun 2021 11:08:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230444AbhFWLK3 (ORCPT ); Wed, 23 Jun 2021 07:10:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46929 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230204AbhFWLJz (ORCPT ); Wed, 23 Jun 2021 07:09:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624446457; 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=r8Kxje9mo0eA1OfdUdQS/iz/Q4P9zCSTZ9JCaTqfbwY=; b=LJ/LrixdY0DomJ1qdS+pxgzhaqOT9CEW3QPgifRTaeoZVKaIBnhZFij+ah/r7f/jxTFVA+ kLUCK/5s/5QAAbBDh0y4J63alDqtBb9vHu880OIZNaygFRrv9yTnccS5c2vT3V2nz1pbAi cVfcT6P/Sikq/Q6I599bWqwd9W4zVIU= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-465-oHdCA3wqOJyQlgJUzHuk0A-1; Wed, 23 Jun 2021 07:07:36 -0400 X-MC-Unique: oHdCA3wqOJyQlgJUzHuk0A-1 Received: by mail-ed1-f70.google.com with SMTP id dy23-20020a05640231f7b0290394996f1452so1093107edb.18 for ; Wed, 23 Jun 2021 04:07:36 -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=r8Kxje9mo0eA1OfdUdQS/iz/Q4P9zCSTZ9JCaTqfbwY=; b=orOKDSy6rBjms9r77f4fF6HpbYh3TlHQctjVTk5bnU4TaDJDGnAM4U2R5VFSRC2TG3 YXOZQPW+d333t6kJzvOCrLSvCZ+VPwe/meXG+AyRnyc0CREmzkfdfgJ2dn0AO/Mml/qt i5Gk4jVISHAmHSG7u7+D2uRcdnW/uFXseMr2rJG0xbKaag8R+ByTyx599IbVt3qOwkh2 I0uCzL5XnIdhX9efAVU8QHBS/0DOb2HMWiYd64p9kFDOrI+ZjW6JZ4/J7jN66RZBkfP2 IIKhP0UXz2cgRuxhkkGwMnHU03kw+RrT/1LSDCDy/QuxhGEQmYx1+bwZKHWGxk2frQ0x W8hg== X-Gm-Message-State: AOAM531r7souSrKqJf3VO+BgE4K0D1Sd1PHdgw9j8quGpntblDwF0yqT m3RNh6UVmoaomUnrsz5CAx8IUWKlGcL9Y5l2Ex9zVms6A9iBebDv+3c/iEf4nUOaF14dPcXVxaO jMm+Joffbvas8usSK X-Received: by 2002:a17:907:2622:: with SMTP id aq2mr9352248ejc.48.1624446455075; Wed, 23 Jun 2021 04:07:35 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx9y32Eh+jTvhrwfrV+XjryvNhw+II0gK5l99fd1c7Gry3y4vk/TmSfoejTBO7gW/Bf7bP9qw== X-Received: by 2002:a17:907:2622:: with SMTP id aq2mr9352206ejc.48.1624446454670; Wed, 23 Jun 2021 04:07:34 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id c15sm10860553edu.19.2021.06.23.04.07.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Jun 2021 04:07:29 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 266CE180737; Wed, 23 Jun 2021 13:07:28 +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" , Jakub Kicinski , =?utf-8?q?Toke_H=C3=B8iland-?= =?utf-8?q?J=C3=B8rgensen?= , Guy Tzalik , Saeed Bishara Subject: [PATCH bpf-next v4 07/19] ena: remove rcu_read_lock() around XDP program invocation Date: Wed, 23 Jun 2021 13:07:15 +0200 Message-Id: <20210623110727.221922-8-toke@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210623110727.221922-1-toke@redhat.com> References: <20210623110727.221922-1-toke@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The ena 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: Guy Tzalik Cc: Saeed Bishara Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/amazon/ena/ena_netdev.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c index 881f88754bf6..a4378b14af4c 100644 --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c @@ -385,7 +385,6 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp) u64 *xdp_stat; int qid; - rcu_read_lock(); xdp_prog = READ_ONCE(rx_ring->xdp_bpf_prog); if (!xdp_prog) @@ -443,8 +442,6 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp) ena_increase_stat(xdp_stat, 1, &rx_ring->syncp); out: - rcu_read_unlock(); - return verdict; }