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-rw-r--r--kernel/sched/clock.c53
1 files changed, 41 insertions, 12 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index 6bd6a6731b21..43c2bcc35761 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -77,35 +77,50 @@ __read_mostly int sched_clock_running;
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
static struct static_key __sched_clock_stable = STATIC_KEY_INIT;
+static int __sched_clock_stable_early;
int sched_clock_stable(void)
{
- if (static_key_false(&__sched_clock_stable))
- return false;
- return true;
+ return static_key_false(&__sched_clock_stable);
}
-void set_sched_clock_stable(void)
+static void __set_sched_clock_stable(void)
{
if (!sched_clock_stable())
- static_key_slow_dec(&__sched_clock_stable);
+ static_key_slow_inc(&__sched_clock_stable);
+}
+
+void set_sched_clock_stable(void)
+{
+ __sched_clock_stable_early = 1;
+
+ smp_mb(); /* matches sched_clock_init() */
+
+ if (!sched_clock_running)
+ return;
+
+ __set_sched_clock_stable();
}
static void __clear_sched_clock_stable(struct work_struct *work)
{
/* XXX worry about clock continuity */
if (sched_clock_stable())
- static_key_slow_inc(&__sched_clock_stable);
+ static_key_slow_dec(&__sched_clock_stable);
}
static DECLARE_WORK(sched_clock_work, __clear_sched_clock_stable);
void clear_sched_clock_stable(void)
{
- if (keventd_up())
- schedule_work(&sched_clock_work);
- else
- __clear_sched_clock_stable(&sched_clock_work);
+ __sched_clock_stable_early = 0;
+
+ smp_mb(); /* matches sched_clock_init() */
+
+ if (!sched_clock_running)
+ return;
+
+ schedule_work(&sched_clock_work);
}
struct sched_clock_data {
@@ -140,6 +155,20 @@ void sched_clock_init(void)
}
sched_clock_running = 1;
+
+ /*
+ * Ensure that it is impossible to not do a static_key update.
+ *
+ * Either {set,clear}_sched_clock_stable() must see sched_clock_running
+ * and do the update, or we must see their __sched_clock_stable_early
+ * and do the update, or both.
+ */
+ smp_mb(); /* matches {set,clear}_sched_clock_stable() */
+
+ if (__sched_clock_stable_early)
+ __set_sched_clock_stable();
+ else
+ __clear_sched_clock_stable(NULL);
}
/*
@@ -340,7 +369,7 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
*/
u64 cpu_clock(int cpu)
{
- if (static_key_false(&__sched_clock_stable))
+ if (!sched_clock_stable())
return sched_clock_cpu(cpu);
return sched_clock();
@@ -355,7 +384,7 @@ u64 cpu_clock(int cpu)
*/
u64 local_clock(void)
{
- if (static_key_false(&__sched_clock_stable))
+ if (!sched_clock_stable())
return sched_clock_cpu(raw_smp_processor_id());
return sched_clock();

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