Messages in this thread | | | Subject | Re: + fix-next_timer_interrupt-for-hrtimer.patch added to -mm tree | From | Thomas Gleixner <> | Date | Sat, 25 Feb 2006 17:17:22 +0100 |
| |
> +#ifdef CONFIG_NO_IDLE_HZ > +/** > + * hrtimer_get_next - get next hrtimer to expire > + * > + * @bases: ktimer base array > + */ > +static inline struct hrtimer *hrtimer_get_next(struct hrtimer_base *bases) > +{ > + unsigned long flags; > + struct hrtimer *timer = NULL; > + int i; > + > + for (i = 0; i < MAX_HRTIMER_BASES; i++) { > + struct hrtimer_base *base; > + struct hrtimer *cur; > + > + base = &bases[i]; > + spin_lock_irqsave(&base->lock, flags); > + cur = rb_entry(base->first, struct hrtimer, node); > + spin_unlock_irqrestore(&base->lock, flags); > + > + if (cur == NULL) > + continue; > + > + if (timer == NULL || cur->expires.tv64 < timer->expires.tv64) > + timer = cur; > + } > + > + return timer; > +}
This is racy on SMP. nanosleep hrtimers are on the stack and can go away due to a signal. posix timers can be removed and destroyed on another CPU.
Also the expires fields of CLOCK_MONOTONIC and CLOCK_REALTIME based tiemrs can not really be compared. Expiry value is absolute time of the respective base clock.
> +/** > + * ktime_to_jiffies - converts ktime to jiffies > + * > + * @event: ktime event to be converted to jiffies > + * > + * Caller must take care of xtime locking. > + */ > +static inline unsigned long ktime_to_jiffies(const ktime_t event) > +{ > + ktime_t now, delta; > + > + now = timespec_to_ktime(xtime); > + delta = ktime_sub(event, now); > + > + return jiffies + (((delta.tv64 * NSEC_CONVERSION) >> > + (NSEC_JIFFIE_SC - SEC_JIFFIE_SC)) >> SEC_JIFFIE_SC); > +}
Only CLOCK_REALTIME based timers are based on xtime. For CLOCK_MONOTONIC based timers this calculation is off by wall_to_monotonic.
> +/** > + * hrtimer_next_jiffie - get next hrtimer event in jiffies > + * > + * Called from next_timer_interrupt() to get the next hrtimer event. > + * Eventually we should change next_timer_interrupt() to return > + * results in nanoseconds instead of jiffies. Caller must host xtime_lock.
S390 does not hold xtime lock when calling next_timer_interrupt !
I look for a sane solution.
tglx
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |