Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755240Ab1EYVQH (ORCPT ); Wed, 25 May 2011 17:16:07 -0400 Received: from casper.infradead.org ([85.118.1.10]:39208 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754887Ab1EYVQG convert rfc822-to-8bit (ORCPT ); Wed, 25 May 2011 17:16:06 -0400 Subject: Re: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM From: Peter Zijlstra To: Marc Zyngier Cc: Ingo Molnar , Frank Rowand , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Oleg Nesterov In-Reply-To: <1306343335.21578.65.camel@twins> References: <1306260792.27474.133.camel@e102391-lin.cambridge.arm.com> <1306272750.2497.79.camel@laptop> <1306343335.21578.65.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 25 May 2011 23:15:28 +0200 Message-ID: <1306358128.21578.107.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2162 Lines: 72 On Wed, 2011-05-25 at 19:08 +0200, Peter Zijlstra wrote: > Ooh, shiny, whilst typing this I got an NMI-watchdog error reporting me > that CPU1 got stuck in try_to_wake_up(), so it looks like I can indeed > reproduce some funnies. > > /me goes dig in. Does the below make your ARM box happy again? It restores the old ttwu behaviour for this case and seems to not mess up my x86 with __ARCH_WANT_INTERRUPTS_ON_CTXSW. Figuring out why the existing condition failed and writing a proper changelog requires a mind that is slightly less deprived of sleep and I shall attempt that tomorrow -- provided this does indeed work for you. --- diff --git a/kernel/sched.c b/kernel/sched.c index 2d12893..6976eac 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2573,7 +2573,19 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu) if (!next) smp_send_reschedule(cpu); } -#endif + +#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW +static void ttwu_activate_remote(struct task_struct *p, int wake_flags) +{ + struct rq *rq = __task_rq_lock(p); + + ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING); + ttwu_do_wakeup(rq, p, wake_flags); + + __task_rq_unlock(rq); +} +#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */ +#endif /* CONFIG_SMP */ static void ttwu_queue(struct task_struct *p, int cpu) { @@ -2630,18 +2642,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) */ while (p->on_cpu) { #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW - /* - * If called from interrupt context we could have landed in the - * middle of schedule(), in this case we should take care not - * to spin on ->on_cpu if p is current, since that would - * deadlock. - */ - if (p == current) { - ttwu_queue(p, cpu); - goto stat; - } -#endif + ttwu_activate_remote(p, wake_flags); + goto stat; +#else cpu_relax(); +#endif } /* * Pairs with the smp_wmb() in finish_lock_switch(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/