Messages in this thread Patch in this message | | | Date | Thu, 23 Feb 2006 17:10:45 -0800 | From | Tony Lindgren <> | Subject | Re: [PATCH] Fix next_timer_interrupt() for hrtimer |
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* john stultz <johnstul@us.ibm.com> [060223 16:50]: > On Thu, 2006-02-23 at 16:40 -0800, Tony Lindgren wrote: > > * john stultz <johnstul@us.ibm.com> [060223 16:37]: > > > On Thu, 2006-02-23 at 16:26 -0800, Tony Lindgren wrote: > > > > + tv = ktime_to_timespec(event); > > > > + > > > > + /* Assume read xtime_lock is held, so we can't use getnstimeofday() */ > > > > + sec = xtime.tv_sec; > > > > + nsec = xtime.tv_nsec; > > > > + while (unlikely(nsec >= NSEC_PER_SEC)) { > > > > + nsec -= NSEC_PER_SEC; > > > > + ++sec; > > > > + } > > > > + tv.tv_sec = sec; > > > > + tv.tv_nsec = nsec; > > > > > > Er, I think you should be able to nest readers. Thus getnstimeofday() > > > should be safe to call. Or is the comment wrong and you are assuming a > > > write lock is held? > > > > Oops, it's a write lock as next_timer_interrupt gets called from > > arch/*/time.c. > > Also the above code just overwrites tv.
That's a bug from clean-up... Actually I just shrunk the ktime_to_jiffies(), see below.
> Do you intend instead to add xtime to tv?
No, just get current time in ktime. But turns out tv is not needed at all :)
Tony This patch adds support for hrtimer to next_timer_interrupt() and fixes current breakage.
Function next_timer_interrupt() got broken with a recent patch 6ba1b91213e81aa92b5cf7539f7d2a94ff54947c as sys_nanosleep() was moved to hrtimer. This broke things as next_timer_interrupt() did not check hrtimer tree for next event.
Function next_timer_interrupt() is needed with dyntick (CONFIG_NO_IDLE_HZ, VST) implementations, as the system can be in idle when next hrtimer event was supposed to happen. At least ARM and S390 currently use next_timer_interrupt().
Signed-off-by: Tony Lindgren <tony@atomide.com>
Index: linux-omap-dev/kernel/hrtimer.c =================================================================== --- linux-omap-dev.orig/kernel/hrtimer.c 2006-02-23 16:19:47.000000000 -0800 +++ linux-omap-dev/kernel/hrtimer.c 2006-02-23 17:04:23.000000000 -0800 @@ -505,6 +505,80 @@ return rem; } +#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; +} + +/** + * ktime_to_jiffies - converts ktime to jiffies + * + * @event: ktime event to be converted + * + * Caller must take care xtime locking. + */ +static inline unsigned long ktime_to_jiffies(const ktime_t event) +{ + ktime_t now, delta; + struct timespec tv; + + now = timespec_to_ktime(xtime); + delta = ktime_sub(event, now); + tv = ktime_to_timespec(delta); + + return jiffies - 1 + timespec_to_jiffies(&tv); +} + +/** + * 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. + */ +int hrtimer_next_jiffie(unsigned long *next_jiffie) +{ + struct hrtimer_base *base = __get_cpu_var(hrtimer_bases); + struct hrtimer * timer; + + timer = hrtimer_get_next(base); + if (timer == NULL) + return -EAGAIN; + + *next_jiffie = ktime_to_jiffies(timer->expires); + + return 0; +} + +#endif + /** * hrtimer_init - initialize a timer to the given clock * Index: linux-omap-dev/kernel/timer.c =================================================================== --- linux-omap-dev.orig/kernel/timer.c 2006-02-23 16:19:47.000000000 -0800 +++ linux-omap-dev/kernel/timer.c 2006-02-23 16:19:47.000000000 -0800 @@ -478,6 +478,7 @@ } #ifdef CONFIG_NO_IDLE_HZ + /* * Find out when the next timer event is due to happen. This * is used on S/390 to stop all activity when a cpus is idle. @@ -489,9 +490,15 @@ struct list_head *list; struct timer_list *nte; unsigned long expires; + unsigned long hr_expires = jiffies + 10 * HZ; /* Anything far ahead */ tvec_t *varray[4]; int i, j; + /* Look for timer events in hrtimer. */ + if ((hrtimer_next_jiffie(&hr_expires) == 0) + && (time_before(hr_expires, jiffies + 2))) + return hr_expires; + base = &__get_cpu_var(tvec_bases); spin_lock(&base->t_base.lock); expires = base->timer_jiffies + (LONG_MAX >> 1); @@ -542,6 +549,10 @@ } } spin_unlock(&base->t_base.lock); + + if (time_before(hr_expires, expires)) + expires = hr_expires; + return expires; } #endif Index: linux-omap-dev/include/linux/hrtimer.h =================================================================== --- linux-omap-dev.orig/include/linux/hrtimer.h 2006-02-23 16:19:43.000000000 -0800 +++ linux-omap-dev/include/linux/hrtimer.h 2006-02-23 16:19:47.000000000 -0800 @@ -115,6 +115,7 @@ /* Query timers: */ extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer); extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp); +extern int hrtimer_next_jiffie(unsigned long *next_jiffie); static inline int hrtimer_active(const struct hrtimer *timer) { | |