get_next_timer_interrupt() returns a delta of (LONG_MAX > 1) in case there is no timer pending. On 64 bit machines this results in a multiplication overflow in tick_nohz_stop_sched_tick(). Reported by: Dave Miller <davem@davemloft.net> Make the return value a constant and limit the return value to a 32 bit value. When the max timeout value is returned, we can safely stop the tick timer device. The max jiffies delta results in a 12 days timeout for HZ=1000. In the long term the get_next_timer_interrupt() code needs to be reworked to return ktime instead of jiffies, but we have to wait until the last users of the original NO_IDLE_HZ code are converted.
Unified · Split
| @@ -68,6 +68,12 @@ extern int del_timer(struct timer_list * timer); · 67 unmodified lines | |||
| 68 | extern int __mod_timer(struct timer_list *timer, unsigned long expires); | 68 | extern int __mod_timer(struct timer_list *timer, unsigned long expires); |
| 69 | extern int mod_timer(struct timer_list *timer, unsigned long expires); | 69 | extern int mod_timer(struct timer_list *timer, unsigned long expires); |
| 70 | 70 | ||
| 71 | /* | ||
| 72 | * The jiffies value which is added to now, when there is no timer | ||
| 73 | * in the timer wheel: | ||
| 74 | */ | ||
| 75 | #define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1) | ||
| 76 | |||
| 71 | /* | 77 | /* |
| 72 | * Return when the next timer-wheel timeout occurs (in absolute jiffies), | 78 | * Return when the next timer-wheel timeout occurs (in absolute jiffies), |
| 73 | * locks the timer base: | 79 | * locks the timer base: |
| @@ -247,6 +247,21 @@ void tick_nohz_stop_sched_tick(void) · 246 unmodified lines | |||
| 247 | if (cpu == tick_do_timer_cpu) | 247 | if (cpu == tick_do_timer_cpu) |
| 248 | tick_do_timer_cpu = -1; | 248 | tick_do_timer_cpu = -1; |
| 249 | 249 | ||
| 250 | ts->idle_sleeps++; | ||
| 251 | |||
| 252 | /* | ||
| 253 | * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that | ||
| 254 | * there is no timer pending or at least extremly far | ||
| 255 | * into the future (12 days for HZ=1000). In this case | ||
| 256 | * we simply stop the tick timer: | ||
| 257 | */ | ||
| 258 | if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) { | ||
| 259 | ts->idle_expires.tv64 = KTIME_MAX; | ||
| 260 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) | ||
| 261 | hrtimer_cancel(&ts->sched_timer); | ||
| 262 | goto out; | ||
| 263 | } | ||
| 264 | |||
| 250 | /* | 265 | /* |
| 251 | * calculate the expiry time for the next timer wheel | 266 | * calculate the expiry time for the next timer wheel |
| 252 | * timer | 267 | * timer |
| @@ -254,7 +269,6 @@ void tick_nohz_stop_sched_tick(void) · 1 unmodified line | |||
| 254 | expires = ktime_add_ns(last_update, tick_period.tv64 * | 269 | expires = ktime_add_ns(last_update, tick_period.tv64 * |
| 255 | delta_jiffies); | 270 | delta_jiffies); |
| 256 | ts->idle_expires = expires; | 271 | ts->idle_expires = expires; |
| 257 | ts->idle_sleeps++; | ||
| 258 | 272 | ||
| 259 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | 273 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| 260 | hrtimer_start(&ts->sched_timer, expires, | 274 | hrtimer_start(&ts->sched_timer, expires, |
| @@ -666,7 +666,7 @@ static inline void __run_timers(tvec_base_t *base) · 665 unmodified lines | |||
| 666 | static unsigned long __next_timer_interrupt(tvec_base_t *base) | 666 | static unsigned long __next_timer_interrupt(tvec_base_t *base) |
| 667 | { | 667 | { |
| 668 | unsigned long timer_jiffies = base->timer_jiffies; | 668 | unsigned long timer_jiffies = base->timer_jiffies; |
| 669 | unsigned long expires = timer_jiffies + (LONG_MAX >> 1); | 669 | unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA; |
| 670 | int index, slot, array, found = 0; | 670 | int index, slot, array, found = 0; |
| 671 | struct timer_list *nte; | 671 | struct timer_list *nte; |
| 672 | tvec_t *varray[4]; | 672 | tvec_t *varray[4]; |
| @@ -752,6 +752,14 @@ static unsigned long cmp_next_hrtimer_event(unsigned long now, · 79 unmodified lines | |||
| 752 | 752 | ||
| 753 | tsdelta = ktime_to_timespec(hr_delta); | 753 | tsdelta = ktime_to_timespec(hr_delta); |
| 754 | delta = timespec_to_jiffies(&tsdelta); | 754 | delta = timespec_to_jiffies(&tsdelta); |
| 755 | |||
| 756 | /* | ||
| 757 | * Limit the delta to the max value, which is checked in | ||
| 758 | * tick_nohz_stop_sched_tick(): | ||
| 759 | */ | ||
| 760 | if (delta > NEXT_TIMER_MAX_DELTA) | ||
| 761 | delta = NEXT_TIMER_MAX_DELTA; | ||
| 762 | |||
| 755 | /* | 763 | /* |
| 756 | * Take rounding errors in to account and make sure, that it | 764 | * Take rounding errors in to account and make sure, that it |
| 757 | * expires in the next tick. Otherwise we go into an endless | 765 | * expires in the next tick. Otherwise we go into an endless |