[patch V2 03/10] timers: Rework idle logic

Thomas Gleixner
2017-04-18T16:42:12Z

[-- Attachment #1: timers--Rework-idle-logic.patch --]
[-- Type: text/plain, Size: 3085 bytes --]

Storing next event and determining whether the base is idle can be done in
__next_timer_interrupt().

Preparatory patch for new call sites which need this information as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/timer.c | 43 ++++++++++++++++++++++++-------------------
1 file changed, 24 insertions(+), 19 deletions(-)

--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1358,8 +1358,11 @@ static int next_pending_bucket(struct ti
/*
* Search the first expiring timer in the various clock levels. Caller must
* hold base->lock.
+ *
+ * Stores the next expiry time in base. The return value indicates whether
+ * the base is empty or not.
*/
-static unsigned long __next_timer_interrupt(struct timer_base *base)
+static bool __next_timer_interrupt(struct timer_base *base)
{
unsigned long clk, next, adj;
unsigned lvl, offset = 0;
@@ -1416,7 +1419,10 @@ static unsigned long __next_timer_interr
clk >>= LVL_CLK_SHIFT;
clk += adj;
}
- return next;
+ /* Store the next event in the base */
+ base->next_expiry = next;
+ /* Return whether the base is empty or not */
+ return next == base->clk + NEXT_TIMER_MAX_DELTA;
}

/*
@@ -1465,7 +1471,7 @@ u64 get_next_timer_interrupt(unsigned lo
struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
u64 expires = KTIME_MAX;
unsigned long nextevt;
- bool is_max_delta;
+ bool is_empty;

/*
* Pretend that there is no timer pending if the cpu is offline.
@@ -1475,9 +1481,8 @@ u64 get_next_timer_interrupt(unsigned lo
return expires;

spin_lock(&base->lock);
- nextevt = __next_timer_interrupt(base);
- is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
- base->next_expiry = nextevt;
+ is_empty = __next_timer_interrupt(base);
+ nextevt = base->next_expiry;
/*
* We have a fresh next event. Check whether we can forward the
* base. We can only do that when @basej is past base->clk
@@ -1490,20 +1495,17 @@ u64 get_next_timer_interrupt(unsigned lo
base->clk = nextevt;
}

- if (time_before_eq(nextevt, basej)) {
- expires = basem;
- base->is_idle = false;
- } else {
- if (!is_max_delta)
- expires = basem + (nextevt - basej) * TICK_NSEC;
- /*
- * If we expect to sleep more than a tick, mark the base idle:
- */
- if ((expires - basem) > TICK_NSEC)
- base->is_idle = true;
- }
+ /* Base is idle if the next event is more than a tick away. */
+ base->is_idle = time_after(nextevt, basej + 1);
spin_unlock(&base->lock);

+ if (!is_empty) {
+ /* If we missed a tick already, force 0 delta */
+ if (time_before_eq(nextevt, basej))
+ nextevt = basej;
+ expires = basem + (nextevt - basej) * TICK_NSEC;
+ }
+
return cmp_next_hrtimer_event(basem, expires);
}

@@ -1534,7 +1536,10 @@ static int collect_expired_timers(struct
* the next expiring timer.
*/
if ((long)(jiffies - base->clk) > 2) {
- unsigned long next = __next_timer_interrupt(base);
+ unsigned long next;
+
+ __next_timer_interrupt(base);
+ next = base->next_expiry;

/*
* If the next timer is ahead of time forward to current