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 79EA2C4332F for ; Wed, 23 Nov 2022 09:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237629AbiKWJX3 (ORCPT ); Wed, 23 Nov 2022 04:23:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237425AbiKWJW7 (ORCPT ); Wed, 23 Nov 2022 04:22:59 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1ECE410CEB1; Wed, 23 Nov 2022 01:22:11 -0800 (PST) Date: Wed, 23 Nov 2022 10:22:08 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1669195329; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7RMwYBxd/qD5IH2N5zIliB0q90C6LaQNXHFoiPeMVds=; b=iBHF1UIYWIlQvLJc+DNDRoM9dbBI4oe+b/iIBptIhLCGgf222ipuJ2ESrIvypVgL7H96je YhJZtUK40AVWOiGBVNn15PAfR9MDBFjPbqzuLui/ZC/g6HtGXSEW2g0C5mYZUrvMdNUK4m OTRTFiFF9JygI9nhYYQVi0+IEOS2/HvUeUNhGPZvYoIlZ9r9SL8+aPsMTwjxLM/9HQ3Axl iuk+pmrGSEqSva/NfDA/vOJvOQnVT29f6y7cZ8cDcjC/+v7CLg0mLUlvDzMFy8T+rcTsWI 4iTBLY5S7BEL77gu/IiGvjf/nm05bIM44nNjIlFpJYMJ5OVok5GdOmoBOcrmZQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1669195329; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7RMwYBxd/qD5IH2N5zIliB0q90C6LaQNXHFoiPeMVds=; b=5Xst4rypB6KjAJo0CRCzi9BjtfZn3S0LF4qAP2RGSLl0LTYmob0DBo4LgG9T44wiBHCdLR EArVEYKQYHKq9eBA== From: Anna-Maria Behnsen To: Thomas Gleixner cc: LKML , Linus Torvalds , Steven Rostedt , 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 V2 12/17] timers: Silently ignore timers with a NULL function In-Reply-To: <20221122173648.793640919@linutronix.de> Message-ID: References: <20221122171312.191765396@linutronix.de> <20221122173648.793640919@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 22 Nov 2022, Thomas Gleixner wrote: > Tearing down timers which have circular dependencies to other > functionality, e.g. workqueues, where the timer can schedule work and work > can arm timers is not trivial. NIT (comma is missing): can arm timer, is not trivial. > In those cases it is desired to shutdown the timer in a way which prevents > rearming of the timer. The mechanism to do so it to set timer->function to s/to do so it/to do so is/ > NULL and use this as an indicator for the timer arming functions to ignore > the (re)arm request. > > In preparation for that replace the warnings in the relevant code pathes > with checks for timer->function == NULL and discard the rearm request > silently. Here is a verb missing that this is a grammatically correct (and understandable) sentence. > Add debug_assert_init() instead of the WARN_ON_ONCE(!timer->function) > checks so that debug objects can warn about non-initialized timers. > > If developers fail to enable debug objects and then waste lots of time to > figure out why their non-initialized timer is not firing, they deserve it. > > Co-developed-by: Steven Rostedt > Signed-off-by: Steven Rostedt > Signed-off-by: Thomas Gleixner > Tested-by: Guenter Roeck > Link: https://lore.kernel.org/all/20220407161745.7d6754b3@gandalf.local.home > Link: https://lore.kernel.org/all/20221110064101.429013735@goodmis.org > --- > V2: Use continue instead of return and amend the return value docs (Steven) > --- > kernel/time/timer.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 55 insertions(+), 5 deletions(-) > > --- a/kernel/time/timer.c > +++ b/kernel/time/timer.c > @@ -1128,8 +1144,12 @@ static inline int > * mod_timer_pending() is the same for pending timers as mod_timer(), but > * will not activate inactive timers. > * > + * If @timer->function == NULL then the start operation is silently > + * discarded. > + * > * Return: > - * * %0 - The timer was inactive and not modified > + * * %0 - The timer was inactive and not modified or was is in > + * shutdown state and the operation was discarded Do you mean "was" or "is"? Please have also a look at the places where you use the same phrase. > * * %1 - The timer was active and requeued to expire at @expires > */ > int mod_timer_pending(struct timer_list *timer, unsigned long expires) > @@ -1155,8 +1175,12 @@ EXPORT_SYMBOL(mod_timer_pending); > * same timer, then mod_timer() is the only safe way to modify the timeout, > * since add_timer() cannot modify an already running timer. > * > + * If @timer->function == NULL then the start operation is silently > + * discarded, the return value is 0 and meaningless. It's easier to read, if you make a dot instead of comma. Thanks, Anna-Maria