sched/clock, x86: Avoid a runtime condition in native_sched_clock()

[platform/adaptation/renesas_rcar/renesas_kernel.git] / arch / x86 / kernel / tsc.c

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 53c1235..6377fb2 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -11,6 +11,7 @@
 #include <linux/clocksource.h>
 #include <linux/percpu.h>
 #include <linux/timex.h>
+#include <linux/static_key.h>
 
 #include <asm/hpet.h>
 #include <asm/timer.h>
@@ -37,6 +38,8 @@ static int __read_mostly tsc_unstable;
    erroneous rdtsc usage on !cpu_has_tsc processors */
 static int __read_mostly tsc_disabled = -1;
 
+static struct static_key __use_tsc = STATIC_KEY_INIT;
+
 int tsc_clocksource_reliable;
 
 /*
@@ -282,7 +285,7 @@ u64 native_sched_clock(void)
         *   very important for it to be as fast as the platform
         *   can achieve it. )
         */
-       if (unlikely(tsc_disabled)) {
+       if (!static_key_false(&__use_tsc)) {
                /* No locking but a rare wrong value is not a big deal: */
                return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
        }
@@ -1193,7 +1196,9 @@ void __init tsc_init(void)
                return;
 
        /* now allow native_sched_clock() to use rdtsc */
+
        tsc_disabled = 0;
+       static_key_slow_inc(&__use_tsc);
 
        if (!no_sched_irq_time)
                enable_sched_clock_irqtime();