On Fri, 2006-01-06 at 14:27 -0800, George Anzinger wrote:
> Steven Rostedt wrote:
> > Thomas,
> ~
>
> > usecs as was shown in the jitter test.
> >
> > My patch does the following:
> >
> > - Changes enqueue_hrtimer from void to int and returns 1 and does
> > nothing else in the case of the timer has passed.
> >
> > - Change hrtimer_start to return 1 if the timer has passed and not when
> > the timer was active. I searched the kernel and I could not find one
> > instance where this hrtimer_start had its return code checked.
> >
> > - Changed schedule_hrtimer to not go to sleep if the time has passed.
>
> At this time the posix timer code depends on the call back. Either you will
> need to make this an option or change that code to do the right thing.
George,
Thanks for showing me this. How about the following patch. It leaves
hrtimer_restart queuing the timer by adding an internal function
__hrtimer_restart that adds the option "queue". Since the only time you
don't want to queue it (that I know of) is internally to nanosleep. But
then again maybe others will want too. But anyway, this keeps the
current API to hrtimers unchanged.
-- Steve
Index: linux-2.6.15-rt2/kernel/hrtimer.c
===================================================================
--- linux-2.6.15-rt2.orig/kernel/hrtimer.c 2006-01-06 17:49:47.000000000 -0500
+++ linux-2.6.15-rt2/kernel/hrtimer.c 2006-01-06 17:53:25.000000000 -0500
@@ -226,6 +226,10 @@
* for which the hrt time source was armed.
*
* Called with interrupts disabled and base lock held
+ *
+ * Returns:
+ * 0 on success
+ * 1 if time has already past.
*/
static int hrtimer_reprogram(struct hrtimer *timer, struct hrtimer_base *base)
{
@@ -239,6 +243,8 @@
res = clockevents_set_next_event(expires);
if (!res)
*expires_next = expires;
+ else
+ res = 1;
return res;
}
@@ -381,11 +387,24 @@
smp_processor_id());
}
+/*
+ * kick_off_hrtimer - queue the timer to the expire list and
+ * raise the hrtimer softirq.
+ */
+static void
+kick_off_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+{
+ list_add_tail(&timer->list, &base->expired);
+ timer->state = HRTIMER_PENDING_CALLBACK;
+ raise_softirq(HRTIMER_SOFTIRQ);
+}
+
#else /* CONFIG_HIGH_RES_TIMERS */
# define hrtimer_hres_active 0
# define hres_enqueue_expired(t,b,n) 0
# define hrtimer_check_clocks() do { } while (0)
+# define kick_off_hrtimer do { } while (0)
#endif /* !CONFIG_HIGH_RES_TIMERS */
@@ -501,9 +520,14 @@
*
* The timer is inserted in expiry order. Insertion into the
* red black tree is O(log(n)). Must hold the base lock.
+ *
+ * Returns:
+ * 0 on success
+ * 1 if time has already past.
*/
-static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+static int enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
{
+
struct rb_node **link = &base->active.rb_node;
struct rb_node *parent = NULL;
struct hrtimer *entry;
@@ -534,12 +558,8 @@
* past we just move it to the expired list
* and schedule the softirq.
*/
- if (hrtimer_hres_active && hrtimer_reprogram(timer, base)) {
- list_add_tail(&timer->list, &base->expired);
- timer->state = HRTIMER_PENDING_CALLBACK;
- raise_softirq(HRTIMER_SOFTIRQ);
- return;
- }
+ if (hrtimer_hres_active && hrtimer_reprogram(timer, base))
+ return 1;
#endif
base->first = &timer->node;
}
@@ -551,6 +571,7 @@
rb_insert_color(&timer->node, &base->active);
timer->state = HRTIMER_PENDING;
+ return 0;
}
/*
@@ -598,10 +619,11 @@
*
* Returns:
* 0 on success
- * 1 when the timer was active
+ * 1 if the time has already past
*/
-int
-hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
+static int
+__hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode,
+ int queue)
{
struct hrtimer_base *base, *new_base;
unsigned long flags;
@@ -610,7 +632,7 @@
base = lock_hrtimer_base(timer, &flags);
/* Remove an active timer from the queue: */
- ret = remove_hrtimer(timer, base);
+ remove_hrtimer(timer, base);
/* Switch the timer base, if necessary: */
new_base = switch_hrtimer_base(timer, base);
@@ -619,13 +641,21 @@
tim = ktime_add(tim, new_base->get_time());
timer->expires = tim;
- enqueue_hrtimer(timer, new_base);
+ if ((ret = enqueue_hrtimer(timer, new_base)) && queue)
+ kick_off_hrtimer(timer, new_base);
unlock_hrtimer_base(timer, &flags);
return ret;
}
+int
+hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
+{
+ return __hrtimer_start(timer, tim, mode, 1);
+}
+
+
/**
* hrtimer_try_to_cancel - try to deactivate a timer
*
@@ -864,9 +894,10 @@
spin_lock_irq(&base->lock);
- if (restart == HRTIMER_RESTART)
- enqueue_hrtimer(timer, base);
- else
+ if (restart == HRTIMER_RESTART) {
+ if (enqueue_hrtimer(timer, base))
+ kick_off_hrtimer(timer, base);
+ } else
timer->state = HRTIMER_EXPIRED;
set_curr_timer(base, NULL);
}
@@ -922,9 +953,10 @@
spin_lock_irq(&base->lock);
- if (restart == HRTIMER_RESTART)
- enqueue_hrtimer(timer, base);
- else
+ if (restart == HRTIMER_RESTART) {
+ if (enqueue_hrtimer(timer, base))
+ kick_off_hrtimer(timer, base);
+ } else
timer->state = HRTIMER_EXPIRED;
set_curr_timer(base, NULL);
}
@@ -983,9 +1015,13 @@
/* fn stays NULL, meaning single-shot wakeup: */
timer->data = current;
- hrtimer_start(timer, timer->expires, mode);
+ if (__hrtimer_start(timer, timer->expires, mode, 0)) {
+ /* time already past */
+ timer->state = HRTIMER_EXPIRED;
+ set_current_state(TASK_RUNNING);
+ } else
+ schedule();
- schedule();
hrtimer_cancel(timer);
/* Return the remaining time: */
@@ -1128,7 +1164,8 @@
timer = rb_entry(node, struct hrtimer, node);
__remove_hrtimer(timer, old_base);
timer->base = new_base;
- enqueue_hrtimer(timer, new_base);
+ if (enqueue_hrtimer(timer, new_base))
+ kick_off_hrtimer(timer, base);
}
}
-
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