Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755217AbbDXNOQ (ORCPT ); Fri, 24 Apr 2015 09:14:16 -0400 Received: from eu-smtp-delivery-143.mimecast.com ([146.101.78.143]:15133 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753797AbbDXNOM (ORCPT ); Fri, 24 Apr 2015 09:14:12 -0400 From: Andreas Sandberg To: linux-kernel@vger.kernel.org Cc: Andreas Sandberg , Thomas Gleixner , Preeti U Murthy , stable@vger.kernel.org, Catalin Marinas , Mark Rutland Subject: [PATCH] tick: Fix hang caused by hrtimer in broadcast mode Date: Fri, 24 Apr 2015 13:06:05 +0000 Message-Id: <1429880765-5558-1-git-send-email-andreas.sandberg@arm.com> X-Mailer: git-send-email 2.1.4 X-OriginalArrivalTime: 24 Apr 2015 13:14:09.0459 (UTC) FILETIME=[8CB1B030:01D07E90] X-MC-Unique: 1TzcNVjUQ7OKZO0cdRU3nw-1 Content-Type: text/plain; charset=WINDOWS-1252 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id t3ODELEa000993 Content-Length: 2231 Lines: 58 The hrtimer callback in the hrtimer's tick broadcast code sometimes incorrectly ends up scheduling events at the current tick causing the kernel to hang servicing the same hrtimer forever. This typically happens when a device is swapped out by tick_install_broadcast_device(), which replaces the event handler with clock_events_handle_noop() and sets the device mode to CLOCK_EVT_MODE_UNUSED. If the timer is scheduled when this happens, the next_event field will not be updated and the hrtimer ends up being restarted at the current tick. To prevent this from happening, only try to restart the hrtimer if the broadcast clock event device is in one of the active modes and try to cancel the timer when entering the CLOCK_EVT_MODE_UNUSED mode. Signed-off-by: Andreas Sandberg Acked-by: Mark Rutland Tested-by: Catalin Marinas --- kernel/time/tick-broadcast-hrtimer.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c index 6aac4be..a20c605 100644 --- a/kernel/time/tick-broadcast-hrtimer.c +++ b/kernel/time/tick-broadcast-hrtimer.c @@ -22,6 +22,7 @@ static void bc_set_mode(enum clock_event_mode mode, struct clock_event_device *bc) { switch (mode) { + case CLOCK_EVT_MODE_UNUSED: case CLOCK_EVT_MODE_SHUTDOWN: /* * Note, we cannot cancel the timer here as we might @@ -99,10 +100,14 @@ static enum hrtimer_restart bc_handler(struct hrtimer *t) { ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer); - if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX) + switch (ce_broadcast_hrtimer.mode) { + case CLOCK_EVT_MODE_PERIODIC: + case CLOCK_EVT_MODE_ONESHOT: + if (ce_broadcast_hrtimer.next_event.tv64 != KTIME_MAX) + return HRTIMER_RESTART; + default: return HRTIMER_NORESTART; - - return HRTIMER_RESTART; + } } void tick_setup_hrtimer_broadcast(void) -- 2.1.4 -- 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/