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>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 9a2264fc42ca..b032317f9964 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1074,8 +1074,8 @@ static DEFINE_PER_CPU(int, printk_pending);
 
 void printk_tick(void)
 {
-        if (__get_cpu_var(printk_pending)) {
-                __get_cpu_var(printk_pending) = 0;
+        if (__this_cpu_read(printk_pending)) {
+                __this_cpu_write(printk_pending, 0);
                 wake_up_interruptible(&log_wait);
         }
 }