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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 144F8C77B72 for ; Sat, 15 Apr 2023 01:02:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229805AbjDOBCM (ORCPT ); Fri, 14 Apr 2023 21:02:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229721AbjDOBCK (ORCPT ); Fri, 14 Apr 2023 21:02:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1976412B for ; Fri, 14 Apr 2023 18:02:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9AF01614E1 for ; Sat, 15 Apr 2023 01:02:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FF15C433D2; Sat, 15 Apr 2023 01:02:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1681520527; bh=3ZqmmZD+fpi3z4npBVCyb7opmMsUf3TJfIoLVIw4dC4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Q7n8Y7W/IHNKtOUo0qHXxbdEH9jxkvvj9GfV67FeFYzyKA86GiJzVAYmoEBSX+9EU 6rHrD9O/TjcLJx5phLqYcQkK61ufOGZLPZBqPmrjY44mY6w4nCkTpq2wyYB/dhZlLB OnkbNkcm5xAnV/ifn0ToZ2/9OtizAPzB6DDUw0bgoyfteGnjB6i+v3nipd5SLA2WxV FjCnGh9wChWcR/i/asnUGZFM7LnSr1PZXtU/Xc/Pl1Ag8bQmTzypDongkm6dtAwydN TYXum20G6ssE/Fqdoc9pEUYLsx52Ro+FYtlNotTcpUG8DRsFPbJ6BSlV4EyEl5cWEp HM4zu5JVUdQSQ== Date: Fri, 14 Apr 2023 18:02:05 -0700 From: Jakub Kicinski To: Hangbin Liu Cc: netdev@vger.kernel.org, Jay Vosburgh , "David S . Miller" , Jonathan Toppins , Paolo Abeni , Eric Dumazet , Liang Li , Simon Horman , Miroslav Lichvar Subject: Re: [PATCHv4 net-next] bonding: add software tx timestamping support Message-ID: <20230414180205.1220135d@kernel.org> In-Reply-To: <20230414083526.1984362-1-liuhangbin@gmail.com> References: <20230414083526.1984362-1-liuhangbin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 14 Apr 2023 16:35:26 +0800 Hangbin Liu wrote: > v4: add ASSERT_RTNL to make sure bond_ethtool_get_ts_info() called via > RTNL. Only check _TX_SOFTWARE for the slaves. > + ASSERT_RTNL(); > + > rcu_read_lock(); > real_dev = bond_option_active_slave_get_rcu(bond); > dev_hold(real_dev); > @@ -5707,10 +5713,36 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev, > ret = ops->get_ts_info(real_dev, info); > goto out; > } > + } else { > + /* Check if all slaves support software tx timestamping */ > + rcu_read_lock(); > + bond_for_each_slave_rcu(bond, slave, iter) { > + ret = -1; > + ops = slave->dev->ethtool_ops; > + phydev = slave->dev->phydev; > + > + if (phy_has_tsinfo(phydev)) > + ret = phy_ts_info(phydev, &ts_info); > + else if (ops->get_ts_info) > + ret = ops->get_ts_info(slave->dev, &ts_info); My comment about this path being under rtnl was to point out that we don't need the RCU protection to iterate over the slaves. This is a bit of a guess, I don't know bonding, but can we not use bond_for_each_slave() ? As a general rule we should let all driver callbacks sleep. Drivers may need to consult the FW or read something over a slow asynchronous bus which requires process / non-atomic context. RCU lock puts us in an atomic context. And ->get_ts_info() is a driver callback. It's not a deal breaker if we can't avoid RCU, but if we can - we should let the drivers sleep. Sorry if I wasn't very clear previously.