[patch V2 06/10] timer: Restructure internal locking

Thomas Gleixner
2017-04-18T16:44:01Z

[-- Attachment #1: timer_Restructure_internal_locking.patch --]
[-- Type: text/plain, Size: 2165 bytes --]

Move the locking out from __run_timers() to the call sites, so the
protected section can be extended at the call site. Preparatory patch for
changing the NOHZ timer placement to a pull at expiry time model.

No functional change.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
kernel/time/timer.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)

--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1651,17 +1651,14 @@ void update_process_times(int user_tick)
/**
* __run_timers - run all expired timers (if any) on this CPU.
* @base: the timer vector to be processed.
+ *
+ * Caller must hold the base lock.
*/
static inline void __run_timers(struct timer_base *base)
{
struct hlist_head heads[LVL_DEPTH];
int levels;

- if (!time_after_eq(jiffies, base->clk))
- return;
-
- spin_lock_irq(&base->lock);
-
while (time_after_eq(jiffies, base->clk)) {

levels = collect_expired_timers(base, heads);
@@ -1671,7 +1668,20 @@ static inline void __run_timers(struct t
expire_timers(base, heads + levels);
}
base->running_timer = NULL;
- spin_unlock_irq(&base->lock);
+}
+
+static void run_timer_base(int index, bool check_nohz)
+{
+ struct timer_base *base = this_cpu_ptr(&timer_bases[index]);
+
+ if (check_nohz && !base->nohz_active)
+ return;
+
+ if (time_after_eq(jiffies, base->clk)) {
+ spin_lock_irq(&base->lock);
+ __run_timers(base);
+ spin_unlock_irq(&base->lock);
+ }
}

/*
@@ -1679,16 +1689,11 @@ static inline void __run_timers(struct t
*/
static __latent_entropy void run_timer_softirq(struct softirq_action *h)
{
- struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
+ run_timer_base(BASE_LOCAL, false);

- __run_timers(base);
if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
- base = this_cpu_ptr(&timer_bases[BASE_GLOBAL]);
- __run_timers(base);
-
- base = this_cpu_ptr(&timer_bases[BASE_DEF]);
- if (base->nohz_active)
- __run_timers(base);
+ run_timer_base(BASE_GLOBAL, false);
+ run_timer_base(BASE_DEF, true);
}
}