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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 490C3C2D0CE for ; Wed, 22 Jan 2020 00:40:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 222A624655 for ; Wed, 22 Jan 2020 00:40:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729058AbgAVAkP (ORCPT ); Tue, 21 Jan 2020 19:40:15 -0500 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:47524 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728665AbgAVAkP (ORCPT ); Tue, 21 Jan 2020 19:40:15 -0500 Received: from localhost (localhost.localdomain [127.0.0.1]) by kvm5.telegraphics.com.au (Postfix) with ESMTP id 31A0222D7F; Tue, 21 Jan 2020 19:40:11 -0500 (EST) Date: Wed, 22 Jan 2020 11:40:09 +1100 (AEDT) From: Finn Thain To: Eric Dumazet cc: "David S. Miller" , Thomas Bogendoerfer , Chris Zankel , Laurent Vivier , Geert Uytterhoeven , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2 01/12] net/sonic: Add mutual exclusion for accessing shared state In-Reply-To: <1b8d9cbe-94cf-2eb6-de44-2a2f9cb0a084@gmail.com> Message-ID: References: <0113c00f-3f77-8324-95a8-31dd6f64fa6a@gmail.com> <1b8d9cbe-94cf-2eb6-de44-2a2f9cb0a084@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 21 Jan 2020, Eric Dumazet wrote: > On 1/21/20 3:33 PM, Finn Thain wrote: > > On Tue, 21 Jan 2020, Eric Dumazet wrote: > > > >> On 1/21/20 1:22 PM, Finn Thain wrote: > >>> The netif_stop_queue() call in sonic_send_packet() races with the > >>> netif_wake_queue() call in sonic_interrupt(). This causes issues > >>> like "NETDEV WATCHDOG: eth0 (macsonic): transmit queue 0 timed out". > >>> Fix this by disabling interrupts when accessing tx_skb[] and next_tx. > >>> Update a comment to clarify the synchronization properties. > >>> > >>> Fixes: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update") > >>> Tested-by: Stan Johnson > >>> Signed-off-by: Finn Thain > >> > >>> @@ -284,9 +287,16 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id) > >>> struct net_device *dev = dev_id; > >>> struct sonic_local *lp = netdev_priv(dev); > >>> int status; > >>> + unsigned long flags; > >>> + > >>> + spin_lock_irqsave(&lp->lock, flags); > >> > >> > >> This is a hard irq handler, no need to block hard irqs. > >> > >> spin_lock() here is enough. > >> > > > > Well, yes, assuming we're dealing with SMP [1]. Probably just disabling > > pre-emption is all that will ever be needed. > > > > Anyway, the real problem solved by disabling irqs is that macsonic must > > avoid re-entrance of sonic_interrupt(). [2] > > > > [1] > > https://lore.kernel.org/netdev/alpine.LNX.2.21.1.2001211026190.8@nippy.intranet/T/#m0523c8b2a26a410ed56889d9230c37ba1160d40a > > > > [2] > > https://lore.kernel.org/netdev/alpine.LNX.2.21.1.2001211026190.8@nippy.intranet/T/#m1c8ca580d2b45e61a628d17839978d0bd5aaf061 > > > I was overlooking the fact that sonic_send_packet() really does have to exclude sonic_interrupt(). So disabling irqs is mandatory here, right? > Oh well... > > I would rather keep the m68k specific wrapper... > If disabling irqs is unavoidable, the wrapper is redundant. > Please add a fat comment of why spin_lock_irqsave() is used, to avoid a > future 'cleanup', since average network developer wont be aware of m68k > oddities. > OK.