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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2011-08-23 15:29:42 +0200
committerThomas Gleixner <tglx@linutronix.de>2011-09-08 11:10:56 +0200
commitd1748302f70be7469809809283fe164156a34231 (patch)
treec81137f4126f2fe1451c28441415c1cd0fa0f7cd /kernel/time/tick-oneshot.c
parent29c158e81c733ac7d6a75c5ee929f34fb9f92983 (diff)
clockevents: Make minimum delay adjustments configurable
The automatic increase of the min_delta_ns of a clockevents device should be done in the clockevents code as the minimum delay is an attribute of the clockevents device. In addition not all architectures want the automatic adjustment, on a massively virtualized system it can happen that the programming of a clock event fails several times in a row because the virtual cpu has been rescheduled quickly enough. In that case the minimum delay will erroneously be increased with no way back. The new config symbol GENERIC_CLOCKEVENTS_MIN_ADJUST is used to enable the automatic adjustment. The config option is selected only for x86. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: john stultz <johnstul@us.ibm.com> Link: http://lkml.kernel.org/r/20110823133142.494157493@de.ibm.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/tick-oneshot.c')
-rw-r--r--kernel/time/tick-oneshot.c77
1 files changed, 4 insertions, 73 deletions
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index 2d04411a5f0..824109060a3 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -21,74 +21,6 @@
#include "tick-internal.h"
-/* Limit min_delta to a jiffie */
-#define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
-
-static int tick_increase_min_delta(struct clock_event_device *dev)
-{
- /* Nothing to do if we already reached the limit */
- if (dev->min_delta_ns >= MIN_DELTA_LIMIT)
- return -ETIME;
-
- if (dev->min_delta_ns < 5000)
- dev->min_delta_ns = 5000;
- else
- dev->min_delta_ns += dev->min_delta_ns >> 1;
-
- if (dev->min_delta_ns > MIN_DELTA_LIMIT)
- dev->min_delta_ns = MIN_DELTA_LIMIT;
-
- printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
- dev->name ? dev->name : "?",
- (unsigned long long) dev->min_delta_ns);
- return 0;
-}
-
-/**
- * tick_program_event internal worker function
- */
-int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
- int force)
-{
- ktime_t now = ktime_get();
- int i;
-
- for (i = 0;;) {
- int ret = clockevents_program_event(dev, expires, now);
-
- if (!ret || !force)
- return ret;
-
- dev->retries++;
- /*
- * We tried 3 times to program the device with the given
- * min_delta_ns. If that's not working then we increase it
- * and emit a warning.
- */
- if (++i > 2) {
- /* Increase the min. delta and try again */
- if (tick_increase_min_delta(dev)) {
- /*
- * Get out of the loop if min_delta_ns
- * hit the limit already. That's
- * better than staying here forever.
- *
- * We clear next_event so we have a
- * chance that the box survives.
- */
- printk(KERN_WARNING
- "CE: Reprogramming failure. Giving up\n");
- dev->next_event.tv64 = KTIME_MAX;
- return -ETIME;
- }
- i = 0;
- }
-
- now = ktime_get();
- expires = ktime_add_ns(now, dev->min_delta_ns);
- }
-}
-
/**
* tick_program_event
*/
@@ -96,7 +28,7 @@ int tick_program_event(ktime_t expires, int force)
{
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
- return tick_dev_program_event(dev, expires, force);
+ return clockevents_program_event(dev, expires, force);
}
/**
@@ -104,11 +36,10 @@ int tick_program_event(ktime_t expires, int force)
*/
void tick_resume_oneshot(void)
{
- struct tick_device *td = &__get_cpu_var(tick_cpu_device);
- struct clock_event_device *dev = td->evtdev;
+ struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
- tick_program_event(ktime_get(), 1);
+ clockevents_program_event(dev, ktime_get(), true);
}
/**
@@ -120,7 +51,7 @@ void tick_setup_oneshot(struct clock_event_device *newdev,
{
newdev->event_handler = handler;
clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
- tick_dev_program_event(newdev, next_event, 1);
+ clockevents_program_event(newdev, next_event, true);
}
/**