On Mon, 2006-02-27 at 19:29 -0800, Tony Lindgren wrote:
> I've changed ARM xtime_lock to read lock, but now there's a slight
> chance that an interrupt adds a timer after next_timer_interrupt() is
> called and before timer is reprogrammed. I believe s390 also has this
> problem.
This needs a more generalized solution later, but I picked up your ARM
change and simplified the hrtimer related bits.
tglx
Index: 2.6.16-rc4-git/arch/arm/kernel/time.c
===================================================================
--- 2.6.16-rc4-git.orig/arch/arm/kernel/time.c
+++ 2.6.16-rc4-git/arch/arm/kernel/time.c
@@ -422,12 +422,14 @@ static int timer_dyn_tick_disable(void)
void timer_dyn_reprogram(void)
{
struct dyn_tick_timer *dyn_tick = system_timer->dyn_tick;
+ unsigned long next, seq;
- if (dyn_tick) {
- write_seqlock(&xtime_lock);
- if (dyn_tick->state & DYN_TICK_ENABLED)
+ if (dyn_tick && (dyn_tick->state & DYN_TICK_ENABLED)) {
+ next = next_timer_interrupt();
+ do {
+ seq = read_seqbegin(&xtime_lock);
dyn_tick->reprogram(next_timer_interrupt() - jiffies);
- write_sequnlock(&xtime_lock);
+ } while (read_seqretry(&xtime_lock, seq));
}
}
Index: 2.6.16-rc4-git/include/linux/hrtimer.h
===================================================================
--- 2.6.16-rc4-git.orig/include/linux/hrtimer.h
+++ 2.6.16-rc4-git/include/linux/hrtimer.h
@@ -116,6 +116,10 @@ extern int hrtimer_try_to_cancel(struct
extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);
+#ifdef CONFIG_NO_IDLE_HZ
+extern ktime_t hrtimer_get_next_event(void);
+#endif
+
static inline int hrtimer_active(const struct hrtimer *timer)
{
return timer->state == HRTIMER_PENDING;
Index: 2.6.16-rc4-git/kernel/hrtimer.c
===================================================================
--- 2.6.16-rc4-git.orig/kernel/hrtimer.c
+++ 2.6.16-rc4-git/kernel/hrtimer.c
@@ -505,6 +505,41 @@ ktime_t hrtimer_get_remaining(const stru
return rem;
}
+#ifdef CONFIG_NO_IDLE_HZ
+/**
+ * hrtimer_get_next_event - get the time until next expiry event
+ *
+ * Returns the delta to the next expiry event or KTIME_MAX if no timer
+ * is pending.
+ */
+ktime_t hrtimer_get_next_event(void)
+{
+ struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
+ ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
+ unsigned long flags;
+ int i;
+
+ for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {
+ struct hrtimer *timer;
+
+ spin_lock_irqsave(&base->lock, flags);
+ if (!base->first) {
+ spin_unlock_irqrestore(&base->lock, flags);
+ continue;
+ }
+ timer = rb_entry(base->first, struct hrtimer, node);
+ delta.tv64 = timer->expires.tv64;
+ spin_unlock_irqrestore(&base->lock, flags);
+ delta = ktime_sub(delta, base->get_time());
+ if (delta.tv64 < mindelta.tv64)
+ mindelta.tv64 = delta.tv64;
+ }
+ if (mindelta.tv64 < 0)
+ mindelta.tv64 = 0;
+ return mindelta;
+}
+#endif
+
/**
* hrtimer_init - initialize a timer to the given clock
*
Index: 2.6.16-rc4-git/kernel/timer.c
===================================================================
--- 2.6.16-rc4-git.orig/kernel/timer.c
+++ 2.6.16-rc4-git/kernel/timer.c
@@ -488,10 +488,21 @@ unsigned long next_timer_interrupt(void)
tvec_base_t *base;
struct list_head *list;
struct timer_list *nte;
- unsigned long expires;
+ unsigned long expires, hr_expires = MAX_JIFFY_OFFSET;
+ ktime_t hr_delta;
tvec_t *varray[4];
int i, j;
+ hr_delta = hrtimer_get_next_event();
+ if (hr_delta.tv64 != KTIME_MAX) {
+ struct timespec tsdelta;
+ tsdelta = ktime_to_timespec(hr_delta);
+ hr_expires = timespec_to_jiffies(&tsdelta);
+ if (hr_expires < 3)
+ return hr_expires + jiffies;
+ }
+ hr_expires += jiffies;
+
base = &__get_cpu_var(tvec_bases);
spin_lock(&base->t_base.lock);
expires = base->timer_jiffies + (LONG_MAX >> 1);
@@ -542,6 +553,10 @@ found:
}
}
spin_unlock(&base->t_base.lock);
+
+ if (time_before(hr_expires, expires))
+ return hr_expires;
+
return expires;
}
#endif
-
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