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 | 68 | extern int __mod_timer(struct timer_list *timer, unsigned long expires); |
| 69 | 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 | 78 | * Return when the next timer-wheel timeout occurs (in absolute jiffies), |
| 73 | 79 | * locks the timer base: |
| @@ -247,6 +247,21 @@ void tick_nohz_stop_sched_tick(void) · 246 unmodified lines | ||
| 247 | 247 | if (cpu == tick_do_timer_cpu) |
| 248 | 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 | 266 | * calculate the expiry time for the next timer wheel |
| 252 | 267 | * timer |
| @@ -254,7 +269,6 @@ void tick_nohz_stop_sched_tick(void) · 1 unmodified line | ||
| 254 | 269 | expires = ktime_add_ns(last_update, tick_period.tv64 * |
| 255 | 270 | delta_jiffies); |
| 256 | 271 | ts->idle_expires = expires; |
| 257 | − ts->idle_sleeps++; | |
| 258 | 272 | |
| 259 | 273 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| 260 | 274 | hrtimer_start(&ts->sched_timer, expires, |
| @@ -666,7 +666,7 @@ static inline void __run_timers(tvec_base_t *base) · 665 unmodified lines | ||
| 666 | 666 | static unsigned long __next_timer_interrupt(tvec_base_t *base) |
| 667 | 667 | { |
| 668 | 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 | 670 | int index, slot, array, found = 0; |
| 671 | 671 | struct timer_list *nte; |
| 672 | 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 | 753 | tsdelta = ktime_to_timespec(hr_delta); |
| 754 | 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 | 764 | * Take rounding errors in to account and make sure, that it |
| 757 | 765 | * expires in the next tick. Otherwise we go into an endless |