Re: BUG: using smp_processor_id() in preemptible code: s2disk

Sergey Senozhatsky
2010-06-14T15:17:35Z

On (06/14/10 08:01), Arjan van de Ven wrote:
> > decided to patch nr_iowait_cpu instead.
>
> the bug is that it needs to be
>
> nr_iowait_cpu(int cpu)
>

Something similar to this?

---

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 52ff8aa..4871ed5 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -137,14 +137,17 @@ static inline int which_bucket(unsigned int duration)
{
int bucket = 0;

+ int cpu = get_cpu();
/*
* We keep two groups of stats; one with no
* IO pending, one without.
* This allows us to calculate
* E(duration)|iowait
*/
- if (nr_iowait_cpu())
+ if (nr_iowait_cpu(cpu))
bucket = BUCKETS/2;
+
+ put_cpu();

if (duration < 10)
return bucket;
@@ -169,14 +172,17 @@ static inline int which_bucket(unsigned int duration)
static inline int performance_multiplier(void)
{
int mult = 1;
-
+ int cpu = get_cpu();
+
/* for higher loadavg, we are more reluctant */

mult += 2 * get_loadavg();

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

+ put_cpu();
+
return mult;
}

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f118809..747fcae 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 f8b8996..f61b48e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2864,9 +2864,9 @@ 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 1d7b9bc..101e8aa 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -159,10 +159,12 @@ update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
ktime_t delta;

if (ts->idle_active) {
+ int cpu = get_cpu();
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);
+ put_cpu();
ts->idle_entrytime = now;
}