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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A53DAC64E8A for ; Mon, 30 Nov 2020 16:53:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 443A32073C for ; Mon, 30 Nov 2020 16:53:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="KTWXa6hK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728865AbgK3Qx3 (ORCPT ); Mon, 30 Nov 2020 11:53:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726769AbgK3Qx2 (ORCPT ); Mon, 30 Nov 2020 11:53:28 -0500 Received: from mail-ot1-x344.google.com (mail-ot1-x344.google.com [IPv6:2607:f8b0:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7E1FC0613D4; Mon, 30 Nov 2020 08:52:48 -0800 (PST) Received: by mail-ot1-x344.google.com with SMTP id 11so11905842oty.9; Mon, 30 Nov 2020 08:52:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=3WA540gSHh8kQNe0lWG+yli/wrKJPqlogKyvN8EdAR0=; b=KTWXa6hK5yeoleLSGEzoPfOiFalYXKt2bSNkbLFYPcRQIsZt+JdyjG++UWPySpxpQ+ 5TXPQcRXjv0DvLrZ3gGwHRXLmmCSiKwCPvdqkc2n9jplKmEOfTrmkjCEzmeI/iGMhy3J zDgxn0BZ4JBFyhAoPJOCFPieYnfIENezF/8PADY9HBAd6Vpo4jMhPzNPY/rZCuFXoLb2 n7rqFzSh8yJPu1amSqOwer9+jgV+1NMSe5VeOsVJxCFC90PtDiyGvJDgGd5Y5hgi9kaS QW9ykI29mhYIdGY6yZ3WZWZKBGunxov1xkm2G1+GjDHMYGMlD5A5h/s7VKSAdyi1GicF xp8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=3WA540gSHh8kQNe0lWG+yli/wrKJPqlogKyvN8EdAR0=; b=jkjXn4/2iZpTij1eEpwJcxoajTvjXZaCYcljQnzQ5jmlGfriNgqkDq3j8LcA41TI6P 1j9OFkFRU/4AnE/y8ChnR2+dpGR5Qww2WO16rOt5A+rM2fcs9ks8qg0Ox1F/1VZODfBA eEWiFBoOwvPGc2GINs4wp/nAusd+DjwD5CxcydCJkmW/kIgeiXjLS3xntHP+Ak5y2lri 7mNSqUwgEOA7+HH3x+DHPIRc/h3do1cbTYZn8gXCX+WeM7ZdlI2YcX8N97nYF4RHF208 NYJh7Yh9ECX8lBXbinq4KM/p4i5nEV16kcn//feoA8Lm+0FaavmU3bGyx8Da/lQCRdg9 fM8w== X-Gm-Message-State: AOAM532H2+3SR1VyOoZY++d2CdR2942ecqYMc4YkPihKM2evJQJARfGG 1xyAkCYTOAF2BhMY+qeh/yoVEXK93MiG07/TyeE2KsfV2g== X-Google-Smtp-Source: ABdhPJy2y/TGo8SvnA68QX0kOXVSSywHbstLw2XAyMQNOLwB1TnHZb6CwaZo4HB3Jk1cbHjd/yhDtb+EXiWOIamw3JA= X-Received: by 2002:a9d:4713:: with SMTP id a19mr17913519otf.132.1606755168216; Mon, 30 Nov 2020 08:52:48 -0800 (PST) MIME-Version: 1.0 References: <20201126220500.av3clcxbbvogvde5@skbuf> <20201127103503.5cda7f24@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> <20201127195057.ac56bimc6z3kpygs@skbuf> <20201127133753.4cf108cb@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> <20201127233048.GB2073444@lunn.ch> <20201127233916.bmhvcep6sjs5so2e@skbuf> <20201128000234.hwd5zo2d4giiikjc@skbuf> <20201128003912.GA2191767@lunn.ch> <20201128014106.lcqi6btkudbnj3mc@skbuf> <20201127181525.2fe6205d@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> In-Reply-To: <20201127181525.2fe6205d@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> From: George McCollister Date: Mon, 30 Nov 2020 10:52:35 -0600 Message-ID: Subject: Re: [PATCH net-next v2 2/3] net: dsa: add Arrow SpeedChips XRS700x driver To: Jakub Kicinski Cc: Vladimir Oltean , Andrew Lunn , Vivien Didelot , Florian Fainelli , "David S . Miller" , netdev@vger.kernel.org, "open list:OPEN FIRMWARE AND..." Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Nov 27, 2020 at 8:15 PM Jakub Kicinski wrote: > > On Sat, 28 Nov 2020 03:41:06 +0200 Vladimir Oltean wrote: > > Jakub, I would like to hear more from you. I would still like to try > > this patch out. You clearly have a lot more background with the code. > > Well, I've seen people run into the problem of this NDO not being able > to sleep, but I don't have much background or knowledge of what impact > the locking will have on real systems. > > We will need to bring this up with Eric (probably best after the turkey > weekend is over). > > In the meantime if you feel like it you may want to add some tracing / > printing to check which processes are accessing /proc/net/dev on your > platforms of interest, see if there is anything surprising. > > > You said in an earlier reply that you should have also documented that > > ndo_get_stats64 is one of the few NDOs that does not take the RTNL. Is > > there a particular reason for that being so, and a reason why it can't > > change? > > I just meant that as a way of documenting the status quo. I'm not aware > of any other place reading stats under RCU (which doesn't mean it > doesn't exist :)). > > That said it is a little tempting to add a new per-netdev mutex here, > instead of congesting RTNL lock further, since today no correct driver > should depend on the RTNL lock. Another possible option could be replacing for_each_netdev_rcu with for_each_netdev_srcu and using list_for_each_entry_srcu (though it's currently used nowhere else in the kernel). Has anyone considered using sleepable RCUs or thought of a reason they wouldn't work or wouldn't be desirable? For more info search for SRCU in Documentation/RCU/RTFP.txt