From patchwork Tue Jun 15 14:54:44 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: 12322077 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=-18.9 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 41167C49EA5 for ; Tue, 15 Jun 2021 14:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F9346161E for ; Tue, 15 Jun 2021 14:55:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231439AbhFOO5S (ORCPT ); Tue, 15 Jun 2021 10:57:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32532 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231466AbhFOO5P (ORCPT ); Tue, 15 Jun 2021 10:57:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623768911; 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=+MBUlWntOqYKNc/Hn434J6hypV0mSyDY5Wc91lYkTgY=; b=S82GwF7aYyQel24j0LCv4tRCDu4woYUk4a4OCyHeU/wltDnJbKhk5drQujxmdIe/X4RQie uk+uZDN1G8OgijWQk1UsZgacXDUiywW0lCbibEzRrbgVc/syMxg0El3vAdrd6I/VQo81Y+ eQ0yRQ4d4/LUDJ2MgpuqJC0NJVr3cpo= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-299-jzbhbBPQNkGCnIdDuUfuPw-1; Tue, 15 Jun 2021 10:55:07 -0400 X-MC-Unique: jzbhbBPQNkGCnIdDuUfuPw-1 Received: by mail-ed1-f71.google.com with SMTP id h23-20020aa7c5d70000b029038fed7b27d5so22254147eds.21 for ; Tue, 15 Jun 2021 07:55:07 -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=+MBUlWntOqYKNc/Hn434J6hypV0mSyDY5Wc91lYkTgY=; b=qvA8wV4EOagSkzVyb6avcwr2e32LIFQO4+yHGkW+Jr2cW6OJfJb79O8+GSbSkZQR7L 8ASx+Ly2n8G4R3t6gYWvjHhtjFvesqYbjD/OstXC8LbcfOoMi+IbuvSnNIxRsGu9DthF t3TLhts+AkWA37VOVX+CCm5E9sXrKI3I0796sArWccOU/pbiY4HIqw/AS/pgrcm1VIoM ldMJBqdhNCWhnSSbWvDyXe2IJkUa6KOinDNw/Mbc1Ps3Ofp4LWPSuM3bqm2skIUh3Ry6 QYKxMFTzvY2XYr3griFI+6IGn1442GvNfv2WHzYC2BsQITqqLdhcw80kgoZFRE1cP1h0 P3QQ== X-Gm-Message-State: AOAM531aJ8K/BpV+RdCv3j78nUXbTa+cgwaEe0CHRABCNM1hItkW/NMz WOL3o2MIfj0TQUw7kGL69DV6E/8J/0F48Ew2LhEbOyAyO5VLIO6AYrgyY9ExuJPIH7VUPCV15gO V3oCZFgK33FFZ X-Received: by 2002:a17:906:340d:: with SMTP id c13mr21721992ejb.457.1623768906643; Tue, 15 Jun 2021 07:55:06 -0700 (PDT) X-Google-Smtp-Source: ABdhPJya4LdcReocWctTCZ9mI36cRWbw1AvtX2B2eEU4jnR/LeLy+2+DqvNbDMZXizkn9MKh2FwH1A== X-Received: by 2002:a17:906:340d:: with SMTP id c13mr21721961ejb.457.1623768906261; Tue, 15 Jun 2021 07:55:06 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id bd3sm12013372edb.34.2021.06.15.07.55.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jun 2021 07:55:04 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id CFF33180728; Tue, 15 Jun 2021 16:54:58 +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-J=C3=B8rgensen?= , Michael Chan Subject: [PATCH bpf-next v2 05/16] bnxt: remove rcu_read_lock() around XDP program invocation Date: Tue, 15 Jun 2021 16:54:44 +0200 Message-Id: <20210615145455.564037-6-toke@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210615145455.564037-1-toke@redhat.com> References: <20210615145455.564037-1-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 bnxt 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: Michael Chan Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c index ec9564e584e0..f38e6ce9b40e 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c @@ -138,9 +138,10 @@ bool bnxt_rx_xdp(struct bnxt *bp, struct bnxt_rx_ring_info *rxr, u16 cons, xdp_prepare_buff(&xdp, *data_ptr - offset, offset, *len, false); orig_data = xdp.data; - rcu_read_lock(); + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ act = bpf_prog_run_xdp(xdp_prog, &xdp); - rcu_read_unlock(); tx_avail = bnxt_tx_avail(bp, txr); /* If the tx ring is not full, we must not update the rx producer yet