sched_clock: delay using sched_clock()

Some arch's can't handle sched_clock() being called too early - delay
this until sched_clock_init() has been called.

Reported-by: Bill Gatliff <bgat@billgatliff.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Nishanth Aravamudan <nacc@us.ibm.com>
CC: Russell King - ARM Linux <linux@arm.linux.org.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 2 deletions

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 074edc989379..204991a0bfa7 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -42,6 +42,8 @@ unsigned long long __attribute__((weak)) sched_clock(void)
         return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
 }
 
+static __read_mostly int sched_clock_running;
+
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
 
 struct sched_clock_data {
@@ -70,8 +72,6 @@ static inline struct sched_clock_data *cpu_sdc(int cpu)
         return &per_cpu(sched_clock_data, cpu);
 }
 
-static __read_mostly int sched_clock_running;
-
 void sched_clock_init(void)
 {
         u64 ktime_now = ktime_to_ns(ktime_get());
@@ -248,6 +248,21 @@ void sched_clock_idle_wakeup_event(u64 delta_ns)
 }
 EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
 
+#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
+
+void sched_clock_init(void)
+{
+        sched_clock_running = 1;
+}
+
+u64 sched_clock_cpu(int cpu)
+{
+        if (unlikely(!sched_clock_running))
+                return 0;
+
+        return sched_clock();
+}
+
 #endif
 
 unsigned long long cpu_clock(int cpu)