core: Replace __get_cpu_var with __this_cpu_read if not used for an address.

__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.

However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes).  Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 3 insertions, 3 deletions

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index b6b898d2eeef..051bc80a0c43 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -49,7 +49,7 @@ struct tick_device *tick_get_device(int cpu)
  */
 int tick_is_oneshot_available(void)
 {
-        struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
+        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
 
         return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
 }
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index aada0e52680a..5cbc101f908b 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -95,7 +95,7 @@ int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
  */
 int tick_program_event(ktime_t expires, int force)
 {
-        struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
+        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
 
         return tick_dev_program_event(dev, expires, force);
 }
@@ -167,7 +167,7 @@ int tick_oneshot_mode_active(void)
         int ret;
 
         local_irq_save(flags);
-        ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
+        ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
         local_irq_restore(flags);
 
         return ret;