From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754391AbbGFPgb (ORCPT ); Mon, 6 Jul 2015 11:36:31 -0400 Received: from www.linutronix.de ([62.245.132.108]:55824 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754338AbbGFPg0 (ORCPT ); Mon, 6 Jul 2015 11:36:26 -0400 Date: Mon, 6 Jul 2015 17:36:21 +0200 (CEST) From: Thomas Gleixner To: Sudeep Holla cc: LKML , Ingo Molnar , Peter Zijlstra , Preeti U Murthy , Andriy Gapon Subject: Re: [patch 2/2] tick/broadcast: Handle spurious interrupts gracefully In-Reply-To: Message-ID: References: <20150705205032.103910828@linutronix.de> <20150705205221.802094647@linutronix.de> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323329-1303444475-1436196982=:3916" 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,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1303444475-1436196982=:3916 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Mon, 6 Jul 2015, Sudeep Holla wrote: > On Sun, Jul 5, 2015 at 9:53 PM, Thomas Gleixner wrote: > > Andriy reported that on a virtual machine the warning about negative > > expiry time in the clock events programming code triggered: > > > > hpet: hpet0 irq 40 for MSI > > hpet: hpet1 irq 41 for MSI > > Switching to clocksource hpet > > WARNING: at kernel/time/clockevents.c:239 > > > > [] clockevents_program_event+0xdb/0xf0 > > [] tick_handle_periodic_broadcast+0x41/0x50 > > [] timer_interrupt+0x15/0x20 > > > > When the second hpet is installed as a per cpu timer the broadcast > > event is not longer required and stopped, which sets the next_evt of > > the broadcast device to KTIME_MAX. > > > > If after that a spurious interrupt happens on the broadcast device, > > then the current code blindly handles it and tries to reprogram the > > broadcast device afterwards, which adds the period to > > next_evt. KTIME_MAX + period results in a negative expiry value > > causing the WARN_ON in the clockevents code to trigger. > > > > Add a proper check for the state of the broadcast device into the > > interrupt handler and return if the interrupt is spurious. > > > > Reported-by: Andriy Gapon > > Signed-off-by: Thomas Gleixner > > --- > > kernel/time/tick-broadcast.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > Index: tip/kernel/time/tick-broadcast.c > > =================================================================== > > --- tip.orig/kernel/time/tick-broadcast.c > > +++ tip/kernel/time/tick-broadcast.c > > @@ -301,6 +301,13 @@ static void tick_handle_periodic_broadca > > bool bc_local; > > > > raw_spin_lock(&tick_broadcast_lock); > > + > > + /* Handle spurious interrupts gracefully */ > > + if (clockevent_state_shutdown(&tick_broadcast_device.evtdev)) { > > I tried this patch along with 1/2, found that this generating warning as > tick_broadcast_device.evtdev is of type ‘struct clock_event_device *’ already, > so it can be passed directly. Right you are. The heat is melting my brain ... --8323329-1303444475-1436196982=:3916--