lkml.org 
[lkml]   [2013]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] tick: make sleep length calculation more accurate
Date
The sleep_length is computed in the tick_nohz_stop_sched_tick function but it
is used later in the code with in between the local irq enabled.

cpu_idle_loop
tick_nohz_idle_enter [ exits with local irq enabled ]
__tick_nohz_idle_enter
tick_nohz_stop_sched_tick
...

arch_cpu_idle
menu_select [ uses here 'sleep_length' ]
...

Between the computation of the sleep length and its usage, some interrupts
can occur, making the sleep length shorter than actually it is.

This patch fixes that by moving the sleep_length computation in the
tick_nohz_get_sleep_length function and store the next_event for the device
instead of the sleep_length.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
include/linux/tick.h | 2 +-
kernel/time/tick-sched.c | 5 +++--
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 5128d33..4932004 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -67,7 +67,7 @@ struct tick_sched {
ktime_t idle_exittime;
ktime_t idle_sleeptime;
ktime_t iowait_sleeptime;
- ktime_t sleep_length;
+ ktime_t next_event;
unsigned long last_jiffies;
unsigned long next_jiffies;
ktime_t idle_expires;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3612fc7..2007a7f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -673,7 +673,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
out:
ts->next_jiffies = next_jiffies;
ts->last_jiffies = last_jiffies;
- ts->sleep_length = ktime_sub(dev->next_event, now);
+ ts->next_event = dev->next_event;

return ret;
}
@@ -837,8 +837,9 @@ void tick_nohz_irq_exit(void)
ktime_t tick_nohz_get_sleep_length(void)
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
+ ktime_t now = ktime_get();

- return ts->sleep_length;
+ return ktime_sub(ts->next_event, now);
}

static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
--
1.7.9.5


\
 
 \ /
  Last update: 2013-09-27 13:21    [W:0.050 / U:19.936 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site