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 877D3C4321E for ; Thu, 10 Nov 2022 21:07:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232084AbiKJVHc (ORCPT ); Thu, 10 Nov 2022 16:07:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230303AbiKJVH3 (ORCPT ); Thu, 10 Nov 2022 16:07:29 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C0C857B5B; Thu, 10 Nov 2022 13:07:27 -0800 (PST) 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 9B41461E60; Thu, 10 Nov 2022 21:07:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39865C433D6; Thu, 10 Nov 2022 21:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668114446; bh=SvL0tC1tE3nUW82Ug4o+iFeGBWUfd1ASGwxtRRbRBIY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=X6yt9egAXwk6xG2LbJRgSeQmEklIyWZA5SD6g3i1mbm/msswMh+cNIlufSBE1fnEP IR8NXRPq/4lBDssPB1ryholDBQqqVPgD0B8e/AesPMnTanXCPFU8xi2brMcWnulkzp lw+FsY5Gmj/CisaT3DjixrbxKgA53rk3HLi+Bnb8hGVMMBA+cDeYCr332lSbl41UxO uytQUD8vnYD8xdCha3JHV2fftWkXYlsO4yb7fEwxnhDgaobuF3LNZ5bWVxk1UT59/h M5K2hQ0mwVjh2h7PIqFEdDT4TkfdhjKVcUC8VV4DgQeNqAltlxc+QodOyapY4K2qVL Edpf9kQpRmwqA== Date: Thu, 10 Nov 2022 23:07:21 +0200 From: Leon Romanovsky To: Jakub Kicinski Cc: Ivan Vecera , "Keller, Jacob E" , "netdev@vger.kernel.org" , "sassmann@redhat.com" , "Piotrowski, Patryk" , SlawomirX Laba , "Brandeburg, Jesse" , "Nguyen, Anthony L" , "David S. Miller" , Eric Dumazet , Paolo Abeni , intel-wired-lan@lists.osuosl.org, open list Subject: Re: [PATCH net] iavf: Do not restart Tx queues after reset task failure Message-ID: References: <20221108102502.2147389-1-ivecera@redhat.com> <20221110155147.1a2c57f6@p1.luc.cera.cz> <20221110122418.32414666@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221110122418.32414666@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 10, 2022 at 12:24:18PM -0800, Jakub Kicinski wrote: > On Thu, 10 Nov 2022 19:07:02 +0200 Leon Romanovsky wrote: > > > > Yes I think you're right. A ton of people check it without the > > > > lock but I think thats not strictly safe. Is dev_close safe to > > > > call when netif_running is false? Why not just remove the check > > > > and always call dev_close then. > > > > > > Check for a bit value (like netif_runnning()) is much cheaper than > > > unconditionally taking global lock like RTNL. > > > > This cheap operation is racy and performed in non-performance > > critical path. > > To be clear - the rtnl_lock around the entire if is still racy > in the grand scheme of things, no? What's stopping someone from > bringing the device right back up after you drop the lock? I want to believe what there is some sort of state machine that won't allow simple toggling of dev_close/dev_open. If it doesn't, rtnl_lock users should audit their code for possible toggling right after that lock is dropped. Anyway, this discussion reminds me our devl_lock debate where we had completely opposite views if rtnl_lock model is the right one. https://lore.kernel.org/netdev/20211101073259.33406da3@kicinski-fedora-PC1C0HJN/ Let's not start argue again, we had enough back then. :) Thanks