From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757762Ab1IATUI (ORCPT ); Thu, 1 Sep 2011 15:20:08 -0400 Received: from www.linutronix.de ([62.245.132.108]:35910 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757575Ab1IATUG (ORCPT ); Thu, 1 Sep 2011 15:20:06 -0400 Date: Thu, 1 Sep 2011 21:20:01 +0200 (CEST) From: Thomas Gleixner To: Liming Wang cc: rt-users , Peter Zijlstra , lkml Subject: Re: [PATCH] mips/rt: convert cascade interrupt non threaded In-Reply-To: <1314370804-21266-1-git-send-email-liming.wang@windriver.com> Message-ID: References: <1314370804-21266-1-git-send-email-liming.wang@windriver.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 26 Aug 2011, Liming Wang wrote: > The preempt_rt kernel forces all irq interrupts to be threaded, > but special interrupts can be excluded from this conversion. > The cascade interrupt should be part of these exceptions. > > In this case, irq2 is initialized before "kthreadd" task, which > converts irq interrupt to threaded. > > If this irq is threaded, the kernel calls "try_to_wake_up" function > to wake up "kthreadd" task, but at that moment, "kthreadd" task > has not been initialized and try_to_wake_up wakes up a NULL task. That's not a reason to mark an interrupt NO_THREAD. The interrupt handler could be non hardirq safe on RT. You'd run into other problems. In the case at hand it's the no_action handler which is hardirq safe on RT and being no_action which means it simply returns IRQ_NONE. I'll queue it for the next rt release and fixup the changelog myself. Thanks, tglx > Signed-off-by: Liming Wang > Signed-off-by: Bruce Ashfield > --- > arch/mips/kernel/i8259.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/arch/mips/kernel/i8259.c b/arch/mips/kernel/i8259.c > index 5c74eb7..fb338db 100644 > --- a/arch/mips/kernel/i8259.c > +++ b/arch/mips/kernel/i8259.c > @@ -295,6 +295,7 @@ static void init_8259A(int auto_eoi) > static struct irqaction irq2 = { > .handler = no_action, > .name = "cascade", > + .flags = IRQF_NO_THREAD, > }; > > static struct resource pic1_io_resource = { > -- > 1.7.0.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >