Add a check to find expired unbound deferrable timers
and trigger softirq for handling timers. This way a CPU
can process all the expired deferrable timers whenever
it is out off idle state due to an interrupt.
Signed-off-by: Prasad Sodagudi <psoda...@codeaurora.org>
---
include/linux/timer.h | 3 +++
kernel/time/tick-sched.c | 8 +++++++-
kernel/time/timer.c | 29 ++++++++++++++++++++++++++++-
3 files changed, 38 insertions(+), 2 deletions(-)
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 0dc19a8..e85dd2d 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -172,6 +172,9 @@ extern int del_timer(struct timer_list * timer);
extern int mod_timer(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
extern int timer_reduce(struct timer_list *timer, unsigned long expires);
+#ifdef CONFIG_SMP
+extern bool check_pending_deferrable_timers(int cpu);
+#endif
/*
* The jiffies value which is added to now, when there is no timer
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3e2dc9b..16aec80 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -23,6 +23,7 @@
#include <linux/module.h>
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
+#include <linux/timer.h>
#include <linux/context_tracking.h>
#include <linux/mm.h>
@@ -1274,8 +1275,13 @@ static inline void tick_nohz_irq_enter(void)
now = ktime_get();
if (ts->idle_active)
tick_nohz_stop_idle(ts, now);
- if (ts->tick_stopped)
+ if (ts->tick_stopped) {
tick_nohz_update_jiffies(now);
+#ifdef CONFIG_SMP
+ if (check_pending_deferrable_timers(smp_processor_id()))
+ raise_softirq_irqoff(TIMER_SOFTIRQ);
+#endif
+ }
}
#else
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1bf9b49..5947c63 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -221,6 +221,7 @@ static DECLARE_WORK(timer_update_work, timer_update_keys);
#ifdef CONFIG_SMP
struct timer_base timer_base_deferrable;
+static atomic_t deferrable_pending;
unsigned int sysctl_timer_migration = 1;
DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
@@ -1610,6 +1611,31 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
}
+
+#ifdef CONFIG_SMP
+/*
+ * check_pending_deferrable_timers - Check for unbound deferrable timer expiry
+ * @cpu - Current CPU
+ *
+ * The function checks whether any global deferrable pending timers
+ * are exipired or not. This function does not check cpu bounded
+ * diferrable pending timers expiry.
+ *
+ * The function returns true when a cpu unbounded deferrable timer is expired.
+ */
+bool check_pending_deferrable_timers(int cpu)
+{
+ if (cpu == tick_do_timer_cpu ||
+ tick_do_timer_cpu == TICK_DO_TIMER_NONE) {
+ if (time_after_eq(jiffies, timer_base_deferrable.clk)
+ && !atomic_cmpxchg(&deferrable_pending, 0, 1)) {
+ return true;
+ }
+ }
+ return false;
+}
+#endif
+
/**
* get_next_timer_interrupt - return the time (clock mono) of the next timer
* @basej: base time jiffies
@@ -1801,7 +1827,8 @@ static __latent_entropy void run_timer_softirq(struct
softirq_action *h)
if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
#ifdef CONFIG_SMP
- if (tick_do_timer_cpu == TICK_DO_TIMER_NONE ||
+ if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
+ tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||
tick_do_timer_cpu == smp_processor_id())
__run_timers(&timer_base_deferrable);
#endif
--
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a Linux Foundation Collaborative Project
