linux-kernel - [PATCH 1/2] hrtimer: reprogram event for expires=KTIME_MAX in hrtimer_force

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Date:	Fri,  9 May 2014 14:10:22 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	tglx@...utronix.de
Cc:	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, arvind.chauhan@....com,
	preeti@...ux.vnet.ibm.com, khilman@...aro.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH 1/2] hrtimer: reprogram event for expires=KTIME_MAX in hrtimer_force_reprogram()

In hrtimer_force_reprogram(), we are reprogramming event device only if the next
timer event is before KTIME_MAX. But what if it is equal to KTIME_MAX? As we
aren't reprogramming it again, it will be set to the last value it was, probably
tick interval, i.e. few milliseconds.

And we will get a interrupt due to that, wouldn't have any hrtimers to service
and return without doing much. But the implementation of event device's driver
may make it more stupid. For example: drivers/clocksource/arm_arch_timer.c
disables the event device only on SHUTDOWN/UNUSED requests in set-mode.
Otherwise, it will keep giving interrupts at tick interval even if
hrtimer_interrupt() didn't reprogram tick..

To get this fixed, lets reprogram event device even for KTIME_MAX, so that the
timer is scheduled for long enough.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 kernel/hrtimer.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6b715c0..b21085c 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -591,8 +591,7 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 	if (cpu_base->hang_detected)
 		return;

-	if (cpu_base->expires_next.tv64 != KTIME_MAX)
-		tick_program_event(cpu_base->expires_next, 1);
+	tick_program_event(cpu_base->expires_next, 1);
 }

 /*
-- 
2.0.0.rc2

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