1 files changed, 14 insertions, 1 deletions

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 390f33234bd0..e1d16c9a7680 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -25,6 +25,7 @@
  * consistent between cpus (never more than 2 jiffies difference).
  */
 #include <linux/spinlock.h>
+#include <linux/hardirq.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/ktime.h>
@@ -37,7 +38,8 @@
  */
 unsigned long long __attribute__((weak)) sched_clock(void)
 {
-        return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
+        return (unsigned long long)(jiffies - INITIAL_JIFFIES)
+                                        * (NSEC_PER_SEC / HZ);
 }
 
 static __read_mostly int sched_clock_running;
@@ -154,6 +156,17 @@ u64 sched_clock_cpu(int cpu)
                 return sched_clock();
 
         scd = cpu_sdc(cpu);
+
+        /*
+         * Normally this is not called in NMI context - but if it is,
+         * trying to do any locking here is totally lethal.
+         */
+        if (unlikely(in_nmi()))
+                return scd->clock;
+
+        if (unlikely(!sched_clock_running))
+                return 0ull;
+
         WARN_ON_ONCE(!irqs_disabled());
         now = sched_clock();