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=-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 3CE4BC48BE8 for ; Tue, 15 Jun 2021 14:55:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 249BA61584 for ; Tue, 15 Jun 2021 14:55:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231379AbhFOO5Q (ORCPT ); Tue, 15 Jun 2021 10:57:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:31261 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231373AbhFOO5M (ORCPT ); Tue, 15 Jun 2021 10:57:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623768907; 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=pWOmo2Dp6By21aiJoC+yh22NhewuBztqhmsfyiwQHMk=; b=NEMRMdHzd5MSDhuRDJJgbmjb496iVQ7TcwcnPE6RlxUxLRighUaXY7dGrcZEG1bDPoutwQ j95+SROQrr0woT6uvoVq/kNGTbIBhm4fwjfdbI4o+xUer6yLhlfcvaCz/PxYAJ1noLCRTt 3h8UEp8XQEEL2nyCEOyCqtENdQDmlfI= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-449-mib89zg6MyWaMoSARM9Abg-1; Tue, 15 Jun 2021 10:55:06 -0400 X-MC-Unique: mib89zg6MyWaMoSARM9Abg-1 Received: by mail-ej1-f70.google.com with SMTP id w13-20020a170906384db02903d9ad6b26d8so4689860ejc.0 for ; Tue, 15 Jun 2021 07:55:06 -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=pWOmo2Dp6By21aiJoC+yh22NhewuBztqhmsfyiwQHMk=; b=OWboMky2Ot0U02DCQu6f7X6s8NhKgjzeqFCIVKsFcvU2IXa29rRr0H/S9H6lpJ3nYB AuKDoWqThBoBJQImwxAEZb8FARz1IYkF6NbCPJ9aM+D57CYHEIKHgmHrzK5D7SgWY0qg uxK8Oy9LDRRuwIxAX59IqK4nYrEwaBhPLNZW9ZqWuW8ou92fRrynVt6jnqqaHT2mTUXH LiIcPVVCmrqg0HHNIqjjJnazbrrgSGeoz30eQnE4AwI9e3MItj2TRMG673SjxSf8AD9f 6eLWzDLsrYPf8quTR7lxPrgF3Ja06C6Ru4elFx1ECOUGudnl54tVx9ubzlyDwkXn9vIP f1Fw== X-Gm-Message-State: AOAM531rtahNyYH3JEmlhJkOPqvHHWAh6Gc1ik6aIkw4g1GbGTiopOdW HPN9XMLhLn4P8EJEIhPIVwSBsow+2FO9cq0PLEOgWw7ddR5JmFj6UPYq+SvziLLSFEo0+WDllzk +QPXTezy41oGxgd8z X-Received: by 2002:a17:906:5ac7:: with SMTP id x7mr5156299ejs.330.1623768905247; Tue, 15 Jun 2021 07:55:05 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzReB1fFu1rxm9m0nqkBN7wrp4chHKHdJVz9CZHmQ8NOXRhVatb2uiKb9hWHsPUxKuHc0Lkog== X-Received: by 2002:a17:906:5ac7:: with SMTP id x7mr5156279ejs.330.1623768905088; Tue, 15 Jun 2021 07:55:05 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id qh23sm10187974ejb.77.2021.06.15.07.55.01 (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 08B1B180735; Tue, 15 Jun 2021 16:54:59 +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?= , Ariel Elior , GR-everest-linux-l2@marvell.com Subject: [PATCH bpf-next v2 12/16] qede: remove rcu_read_lock() around XDP program invocation Date: Tue, 15 Jun 2021 16:54:51 +0200 Message-Id: <20210615145455.564037-13-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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The qede 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: Ariel Elior Cc: GR-everest-linux-l2@marvell.com Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/qlogic/qede/qede_fp.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/drivers/net/ethernet/qlogic/qede/qede_fp.c b/drivers/net/ethernet/qlogic/qede/qede_fp.c index 8e150dd4f899..d806ab925cee 100644 --- a/drivers/net/ethernet/qlogic/qede/qede_fp.c +++ b/drivers/net/ethernet/qlogic/qede/qede_fp.c @@ -1089,13 +1089,10 @@ static bool qede_rx_xdp(struct qede_dev *edev, xdp_prepare_buff(&xdp, page_address(bd->data), *data_offset, *len, false); - /* Queues always have a full reset currently, so for the time - * being until there's atomic program replace just mark read - * side for map helpers. + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. */ - rcu_read_lock(); act = bpf_prog_run_xdp(prog, &xdp); - rcu_read_unlock(); /* Recalculate, as XDP might have changed the headers */ *data_offset = xdp.data - xdp.data_hard_start; -- 2.31.1