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 7C628C4332F for ; Mon, 21 Nov 2022 20:19:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231289AbiKUUTE (ORCPT ); Mon, 21 Nov 2022 15:19:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229628AbiKUUTA (ORCPT ); Mon, 21 Nov 2022 15:19:00 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2B81BF5AA; Mon, 21 Nov 2022 12:18:59 -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 ams.source.kernel.org (Postfix) with ESMTPS id 98D51B81233; Mon, 21 Nov 2022 20:18:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 448C6C433C1; Mon, 21 Nov 2022 20:18:55 +0000 (UTC) Date: Mon, 21 Nov 2022 15:18:50 -0500 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , Linus Torvalds , Anna-Maria Behnsen , Peter Zijlstra , Stephen Boyd , Guenter Roeck , Andrew Morton , Julia Lawall , Arnd Bergmann , Viresh Kumar , Marc Zyngier , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-bluetooth@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org Subject: Re: [patch 05/15] timers: Replace BUG_ON()s Message-ID: <20221121151850.635d3883@gandalf.local.home> In-Reply-To: <20221115202117.267934419@linutronix.de> References: <20221115195802.415956561@linutronix.de> <20221115202117.267934419@linutronix.de> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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 Tue, 15 Nov 2022 21:28:41 +0100 (CET) Thomas Gleixner wrote: > The timer code still has a few BUG_ON()s left which are crashing the kernel > in situations where it still can recover or simply refuse to take an > action. > > Remove the one in the hotplug callback which checks for the CPU being > offline. If that happens then the whole hotplug machinery will explode in > colourful ways. > > Replace the rest with WARN_ON_ONCE() and conditional returns where > appropriate. > > Signed-off-by: Thomas Gleixner > --- > kernel/time/timer.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > --- a/kernel/time/timer.c > +++ b/kernel/time/timer.c > @@ -1193,7 +1193,8 @@ EXPORT_SYMBOL(timer_reduce); > */ > void add_timer(struct timer_list *timer) > { > - BUG_ON(timer_pending(timer)); > + if (WARN_ON_ONCE(timer_pending(timer))) > + return; > __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); > } > EXPORT_SYMBOL(add_timer); > @@ -1210,7 +1211,8 @@ void add_timer_on(struct timer_list *tim > struct timer_base *new_base, *base; > unsigned long flags; > > - BUG_ON(timer_pending(timer) || !timer->function); > + if (WARN_ON_ONCE(timer_pending(timer) || !timer->function)) > + return; > > new_base = get_timer_cpu_base(timer->flags, cpu); > I wonder if this patch should be split up into two patches, as the above is trivial and the below is a bit more "complex". Although it's probably moot as none of these should ever trigger. > @@ -2017,8 +2019,6 @@ int timers_dead_cpu(unsigned int cpu) > struct timer_base *new_base; > int b, i; > > - BUG_ON(cpu_online(cpu)); > - > for (b = 0; b < NR_BASES; b++) { > old_base = per_cpu_ptr(&timer_bases[b], cpu); > new_base = get_cpu_ptr(&timer_bases[b]); > @@ -2035,7 +2035,8 @@ int timers_dead_cpu(unsigned int cpu) > */ > forward_timer_base(new_base); > > - BUG_ON(old_base->running_timer); > + WARN_ON_ONCE(old_base->running_timer); > + old_base->running_timer = NULL; I guess interesting things could happen if running_timer was not NULL, but again, WARN_ON_ONCE() should never be triggered in a correctly running kernel. Reviewed-by: Steven Rostedt (Google) -- Steve > > for (i = 0; i < WHEEL_SIZE; i++) > migrate_timer_list(new_base, old_base->vectors + i);