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From: Peter Zijlstra on 1 Jul 2010 03:10
With 0224cf4c5e (sched: Intoduce get_cpu_iowait_time_us()) Arjan broke
things by not making sure preemption was indeed disabled by the callers
of nr_iowait_cpu() which took the iowait value of the current cpu.

This resulted in a heap of preempt warnings. Cure this by making
nr_iowait_cpu() take a cpu number and fix up the callers to pass in the
right number.

Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
---
Confirmed to work..

drivers/cpuidle/governors/menu.c | 4 ++--
include/linux/sched.h | 2 +-
kernel/sched.c | 4 ++--
kernel/time/tick-sched.c | 16 ++++++++--------
4 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 52ff8aa..1b12870 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -143,7 +143,7 @@ static inline int which_bucket(unsigned int duration)
* This allows us to calculate
* E(duration)|iowait
*/
- if (nr_iowait_cpu())
+ if (nr_iowait_cpu(smp_processor_id()))
bucket = BUCKETS/2;

if (duration < 10)
@@ -175,7 +175,7 @@ static inline int performance_multiplier(void)
mult += 2 * get_loadavg();

/* for IO wait tasks (per cpu!) we add 5x each */
- mult += 10 * nr_iowait_cpu();
+ mult += 10 * nr_iowait_cpu(smp_processor_id());

return mult;
}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a61c08c..1f25798 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -139,7 +139,7 @@ extern int nr_processes(void);
extern unsigned long nr_running(void);
extern unsigned long nr_uninterruptible(void);
extern unsigned long nr_iowait(void);
-extern unsigned long nr_iowait_cpu(void);
+extern unsigned long nr_iowait_cpu(int cpu);
extern unsigned long this_cpu_load(void);


diff --git a/kernel/sched.c b/kernel/sched.c
index 71e3dc8..d3c0262 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2946,9 +2946,9 @@ unsigned long nr_iowait(void)
return sum;
}

-unsigned long nr_iowait_cpu(void)
+unsigned long nr_iowait_cpu(int cpu)
{
- struct rq *this = this_rq();
+ struct rq *this = cpu_rq(cpu);
return atomic_read(&this->nr_iowait);
}

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index e0707ea..17525ca 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -154,14 +154,14 @@ static void tick_nohz_update_jiffies(ktime_t now)
* Updates the per cpu time idle statistics counters
*/
static void
-update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
+update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
{
ktime_t delta;

if (ts->idle_active) {
delta = ktime_sub(now, ts->idle_entrytime);
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
- if (nr_iowait_cpu() > 0)
+ if (nr_iowait_cpu(cpu) > 0)
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
ts->idle_entrytime = now;
}
@@ -175,19 +175,19 @@ static void tick_nohz_stop_idle(int cpu, ktime_t now)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);

- update_ts_time_stats(ts, now, NULL);
+ update_ts_time_stats(cpu, ts, now, NULL);
ts->idle_active = 0;

sched_clock_idle_wakeup_event(0);
}

-static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
+static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
{
ktime_t now;

now = ktime_get();

- update_ts_time_stats(ts, now, NULL);
+ update_ts_time_stats(cpu, ts, now, NULL);

ts->idle_entrytime = now;
ts->idle_active = 1;
@@ -216,7 +216,7 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
if (!tick_nohz_enabled)
return -1;

- update_ts_time_stats(ts, ktime_get(), last_update_time);
+ update_ts_time_stats(cpu, ts, ktime_get(), last_update_time);

return ktime_to_us(ts->idle_sleeptime);
}
@@ -242,7 +242,7 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
if (!tick_nohz_enabled)
return -1;

- update_ts_time_stats(ts, ktime_get(), last_update_time);
+ update_ts_time_stats(cpu, ts, ktime_get(), last_update_time);

return ktime_to_us(ts->iowait_sleeptime);
}
@@ -284,7 +284,7 @@ void tick_nohz_stop_sched_tick(int inidle)
*/
ts->inidle = 1;

- now = tick_nohz_start_idle(ts);
+ now = tick_nohz_start_idle(cpu, ts);

/*
* If this cpu is offline and it is the one which updates

--
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Next: What's the relationship between Linux driver running priority and FIFO policy?