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sched: fix rq->clock overflows detection with CONFIG_NO_HZ 

When using CONFIG_NO_HZ, rq->tick_timestamp is not updated every TICK_NSEC.
We check that the number of skipped ticks matches the clock jump seen in
__update_rq_clock().

Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Guillaume Chazarain 2008-04-19 19:44:57 +02:00 committed by Ingo Molnar
parent 30914a58af
commit 15934a3732
1 changed files with 35 additions and 3 deletions
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38
kernel/sched.c
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@ -397,6 +397,7 @@ struct rq {
unsigned long cpu_load[CPU_LOAD_IDX_MAX];
unsigned char idle_at_tick;
#ifdef CONFIG_NO_HZ
unsigned long last_tick_seen;
unsigned char in_nohz_recently;
#endif
/* capture load from *all* tasks on this cpu: */
@ -500,6 +501,32 @@ static inline int cpu_of(struct rq *rq)
#endif
}
#ifdef CONFIG_NO_HZ
static inline bool nohz_on(int cpu)
{
return tick_get_tick_sched(cpu)->nohz_mode != NOHZ_MODE_INACTIVE;
}
static inline u64 max_skipped_ticks(struct rq *rq)
{
return nohz_on(cpu_of(rq)) ? jiffies - rq->last_tick_seen + 2 : 1;
}
static inline void update_last_tick_seen(struct rq *rq)
{
rq->last_tick_seen = jiffies;
}
#else
static inline u64 max_skipped_ticks(struct rq *rq)
{
return 1;
}
static inline void update_last_tick_seen(struct rq *rq)
{
}
#endif
/*
* Update the per-runqueue clock, as finegrained as the platform can give
* us, but without assuming monotonicity, etc.:
@ -524,9 +551,12 @@ static void __update_rq_clock(struct rq *rq)
/*
* Catch too large forward jumps too:
*/
if (unlikely(clock + delta > rq->tick_timestamp + TICK_NSEC)) {
if (clock < rq->tick_timestamp + TICK_NSEC)
clock = rq->tick_timestamp + TICK_NSEC;
u64 max_jump = max_skipped_ticks(rq) * TICK_NSEC;
u64 max_time = rq->tick_timestamp + max_jump;
if (unlikely(clock + delta > max_time)) {
if (clock < max_time)
clock = max_time;
else
clock++;
rq->clock_overflows++;
@ -3812,6 +3842,7 @@ void scheduler_tick(void)
rq->clock_underflows++;
}
rq->tick_timestamp = rq->clock;
update_last_tick_seen(rq);
update_cpu_load(rq);
curr->sched_class->task_tick(rq, curr, 0);
update_sched_rt_period(rq);
@ -7261,6 +7292,7 @@ void __init sched_init(void)
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->clock = 1;
update_last_tick_seen(rq);
init_cfs_rq(&rq->cfs, rq);
init_rt_rq(&rq->rt, rq);
#ifdef CONFIG_FAIR_GROUP_SCHED