From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752412AbaDWItr (ORCPT ); Wed, 23 Apr 2014 04:49:47 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43485 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbaDWItn (ORCPT ); Wed, 23 Apr 2014 04:49:43 -0400 Date: Wed, 23 Apr 2014 10:49:37 +0200 From: Peter Zijlstra To: Sebastian Andrzej Siewior Cc: Steven Rostedt , Stanislav Meduna , "linux-rt-users@vger.kernel.org" , Linux ARM Kernel , "linux-kernel@vger.kernel.org" , Thomas Gleixner Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 Message-ID: <20140423084937.GH11096@twins.programming.kicks-ass.net> References: <534C3606.7010206@meduna.org> <534C731F.1050406@meduna.org> <534DADF1.6060608@meduna.org> <20140422115439.GA20669@linutronix.de> <20140422094657.5b6ca1e2@gandalf.local.home> <53569E05.8010600@linutronix.de> <20140422134802.73fc1fa4@gandalf.local.home> <20140422141650.7f43d5ba@gandalf.local.home> <53576859.8060706@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53576859.8060706@linutronix.de> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 23, 2014 at 09:14:33AM +0200, Sebastian Andrzej Siewior wrote: > On 04/22/2014 08:16 PM, Steven Rostedt wrote: > > --- a/kernel/timer.c > > +++ b/kernel/timer.c > > @@ -1447,6 +1447,12 @@ static void run_timer_softirq(struct softirq_action *h) > > __run_timers(base); > > } > > > > +#ifdef CONFIG_SMP > > +#define timer_should_raise_softirq(lock) !spin_do_trylock(lock) > > +#else > > +#define timer_should_raise_softirq(lock) 1 > > +#endif > > + > > No. The lock may be taken but it also may be available no matter if UP > or not. With this patch applied the lockdep splat will go away but the > FULL_NO_HZ people will come back because the timer softirq is scheduled > even if no timer has expired. You can do FULL_NO_HZ on UP ? That seems rather pointless, as there isn't a 'spare' CPU to do all the timekeeping on. From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz@infradead.org (Peter Zijlstra) Date: Wed, 23 Apr 2014 10:49:37 +0200 Subject: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 In-Reply-To: <53576859.8060706@linutronix.de> References: <534C3606.7010206@meduna.org> <534C731F.1050406@meduna.org> <534DADF1.6060608@meduna.org> <20140422115439.GA20669@linutronix.de> <20140422094657.5b6ca1e2@gandalf.local.home> <53569E05.8010600@linutronix.de> <20140422134802.73fc1fa4@gandalf.local.home> <20140422141650.7f43d5ba@gandalf.local.home> <53576859.8060706@linutronix.de> Message-ID: <20140423084937.GH11096@twins.programming.kicks-ass.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Apr 23, 2014 at 09:14:33AM +0200, Sebastian Andrzej Siewior wrote: > On 04/22/2014 08:16 PM, Steven Rostedt wrote: > > --- a/kernel/timer.c > > +++ b/kernel/timer.c > > @@ -1447,6 +1447,12 @@ static void run_timer_softirq(struct softirq_action *h) > > __run_timers(base); > > } > > > > +#ifdef CONFIG_SMP > > +#define timer_should_raise_softirq(lock) !spin_do_trylock(lock) > > +#else > > +#define timer_should_raise_softirq(lock) 1 > > +#endif > > + > > No. The lock may be taken but it also may be available no matter if UP > or not. With this patch applied the lockdep splat will go away but the > FULL_NO_HZ people will come back because the timer softirq is scheduled > even if no timer has expired. You can do FULL_NO_HZ on UP ? That seems rather pointless, as there isn't a 'spare' CPU to do all the timekeeping on.