From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756074Ab2GXUyg (ORCPT ); Tue, 24 Jul 2012 16:54:36 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:34498 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754722Ab2GXUyf (ORCPT ); Tue, 24 Jul 2012 16:54:35 -0400 Message-ID: <500F0BAB.7060001@gmail.com> Date: Tue, 24 Jul 2012 22:55:07 +0200 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120713 Thunderbird/13.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: "linux-kernel@vger.kernel.org" Subject: Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6 References: <500ED719.2010002@gmail.com> <20120724174017.GE2390@linux.vnet.ibm.com> In-Reply-To: <20120724174017.GE2390@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/24/2012 07:40 PM, Paul E. McKenney wrote: > The interrupt flag is zero, so interrupts are disabled. So my question > to you is "Why did do_pageattr_test() or one of the functions it called > disable interrupts for more than one hundred thousand jiffies?" > > I can't see where it is disabling interrupts, but the EFLAGS register > above does indicate that they are disabled. Or is this something useless > that is just telling us that receiving the NMI disabled interrupts? Doesn't the stack of CPU1 show that it's currently handling an interrupt: [ 215.026612] Call Trace: [ 215.026612] [ 215.026612] [] native_apic_msr_eoi_write+0x27/0x30 [ 215.026612] [] smp_apic_timer_interrupt+0x34/0xa0 [ 215.026612] [] apic_timer_interrupt+0x6f/0x80 [ 215.026612] Or am I reading that wrong? In that case, it had nothing to do with pageattr which just happened to be on the stack at that time.