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Subject[PATCH v9 07/10] time: hrtimer: Introduce hrtimer_next_event_without()
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

The next set of changes will need to compute the time to the next
hrtimer event over all hrtimers except for the scheduler tick one.

To that end introduce a new helper function,
hrtimer_next_event_without(), for computing the time until the next
hrtimer event over all timers except for one and modify the underlying
code in __hrtimer_next_event_base() to prepare it for being called by
that new function.

No intentional changes in functionality.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

v8 -> v9:
* Make fewer changes to the existing code.
* Add a new helper function for the handling of the use case at hand.

---
include/linux/hrtimer.h | 1
kernel/time/hrtimer.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 54 insertions(+), 2 deletions(-)

Index: linux-pm/include/linux/hrtimer.h
===================================================================
--- linux-pm.orig/include/linux/hrtimer.h
+++ linux-pm/include/linux/hrtimer.h
@@ -426,6 +426,7 @@ static inline ktime_t hrtimer_get_remain
}

extern u64 hrtimer_get_next_event(void);
+extern u64 hrtimer_next_event_without(const struct hrtimer *exclude);

extern bool hrtimer_active(const struct hrtimer *timer);

Index: linux-pm/kernel/time/hrtimer.c
===================================================================
--- linux-pm.orig/kernel/time/hrtimer.c
+++ linux-pm/kernel/time/hrtimer.c
@@ -490,6 +490,7 @@ __next_base(struct hrtimer_cpu_base *cpu
while ((base = __next_base((cpu_base), &(active))))

static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
+ const struct hrtimer *exclude,
unsigned int active,
ktime_t expires_next)
{
@@ -502,9 +503,24 @@ static ktime_t __hrtimer_next_event_base

next = timerqueue_getnext(&base->active);
timer = container_of(next, struct hrtimer, node);
+ if (timer == exclude) {
+ /* Get to the next timer in the queue. */
+ struct rb_node *rbn = rb_next(&next->node);
+
+ next = rb_entry_safe(rbn, struct timerqueue_node, node);
+ if (!next)
+ continue;
+
+ timer = container_of(next, struct hrtimer, node);
+ }
expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
if (expires < expires_next) {
expires_next = expires;
+
+ /* Skip cpu_base update if a timer is being excluded. */
+ if (exclude)
+ continue;
+
if (timer->is_soft)
cpu_base->softirq_next_timer = timer;
else
@@ -548,7 +564,8 @@ __hrtimer_get_next_event(struct hrtimer_
if (!cpu_base->softirq_activated && (active_mask & HRTIMER_ACTIVE_SOFT)) {
active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
cpu_base->softirq_next_timer = NULL;
- expires_next = __hrtimer_next_event_base(cpu_base, active, KTIME_MAX);
+ expires_next = __hrtimer_next_event_base(cpu_base, NULL,
+ active, KTIME_MAX);

next_timer = cpu_base->softirq_next_timer;
}
@@ -556,7 +573,8 @@ __hrtimer_get_next_event(struct hrtimer_
if (active_mask & HRTIMER_ACTIVE_HARD) {
active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
cpu_base->next_timer = next_timer;
- expires_next = __hrtimer_next_event_base(cpu_base, active, expires_next);
+ expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
+ expires_next);
}

return expires_next;
@@ -1200,6 +1218,39 @@ u64 hrtimer_get_next_event(void)

raw_spin_unlock_irqrestore(&cpu_base->lock, flags);

+ return expires;
+}
+
+/**
+ * hrtimer_next_event_without - time until next expiry event w/o one timer
+ * @exclude: timer to exclude
+ *
+ * Returns the next expiry time over all timers except for the @exclude one or
+ * KTIME_MAX if none of them is pending.
+ */
+u64 hrtimer_next_event_without(const struct hrtimer *exclude)
+{
+ struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+ u64 expires = KTIME_MAX;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&cpu_base->lock, flags);
+
+ if (__hrtimer_hres_active(cpu_base)) {
+ unsigned int active;
+
+ if (!cpu_base->softirq_activated) {
+ active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
+ expires = __hrtimer_next_event_base(cpu_base, exclude,
+ active, KTIME_MAX);
+ }
+ active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
+ expires = __hrtimer_next_event_base(cpu_base, exclude, active,
+ expires);
+ }
+
+ raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+
return expires;
}
#endif
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