* john stultz <[email protected]> [060223 16:50]:
> On Thu, 2006-02-23 at 16:40 -0800, Tony Lindgren wrote:
> > * john stultz <[email protected]> [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 <[email protected]>
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)
{
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