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Message-Id: <20160904012852.17814-6-nicstange@gmail.com>
Date: Sun, 4 Sep 2016 03:28:46 +0200
From: Nicolai Stange <nicstange@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: John Stultz <john.stultz@...aro.org>, linux-kernel@...r.kernel.org,
Nicolai Stange <nicstange@...il.com>
Subject: [RFC v5 17/23] clockevents: use ->min_delta_ticks_adjusted to program minimum delta
The use of a clockevent device's ->min_delta_ns in the event programming
path hinders upcoming changes to the clockevent core making it NTP
correction aware: both, ->mult and ->min_delta_ns would need to get
updated as well as consumed atomically and we'd rather like to avoid any
locking here.
We already have got ->min_delta_ticks_adjusted which
- resembles the value of ->min_delta_ns
- and is guaranteed to be always >= the hardware's hard limit
->min_delta_ticks and thus, can be used w/o locking as we don't care
for small deviations.
In both implementations of clockevents_program_min_delta(),
don't calculate the event's deadline from ->min_delta_ns, but use its
drop-in replacement ->min_delta_ticks_adjusted.
Signed-off-by: Nicolai Stange <nicstange@...il.com>
---
kernel/time/clockevents.c | 15 ++-------------
1 file changed, 2 insertions(+), 13 deletions(-)
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 8983fee..aa7b325 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -246,19 +246,14 @@ static int clockevents_increase_min_delta(struct clock_event_device *dev)
*/
static int clockevents_program_min_delta(struct clock_event_device *dev)
{
- unsigned long long clc;
- int64_t delta;
int i;
for (i = 0;;) {
- delta = dev->min_delta_ns;
-
if (clockevent_state_shutdown(dev))
return 0;
dev->retries++;
- clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
- if (dev->set_next_event((unsigned long) clc, dev) == 0)
+ if (!dev->set_next_event(dev->min_delta_ticks_adjusted, dev))
return 0;
if (++i > 2) {
@@ -284,17 +279,11 @@ static int clockevents_program_min_delta(struct clock_event_device *dev)
*/
static int clockevents_program_min_delta(struct clock_event_device *dev)
{
- unsigned long long clc;
- int64_t delta;
-
- delta = dev->min_delta_ns;
-
if (clockevent_state_shutdown(dev))
return 0;
dev->retries++;
- clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
- return dev->set_next_event((unsigned long) clc, dev);
+ return dev->set_next_event(dev->min_delta_ticks_adjusted, dev);
}
#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
--
2.9.3
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