drivers: 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
determed (since its an implied address conversion through segment prefixes).
Therefore apply this only to uses of __get_cpu_var where the addres of the
variable is not used.

V3->V4:
	- Move one instance of this_cpu_inc_return to a later patch
	  so that this one can go in without percpu infrastructrure
	  changes.

Sedat: fixed compile failure caused by an extra ')'.

Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
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, 3 insertions, 3 deletions

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index dcb38f8ddfda..a765b823aa9e 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -746,7 +746,7 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
         struct acpi_processor *pr;
         struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
 
-        pr = __get_cpu_var(processors);
+        pr = __this_cpu_read(processors);
 
         if (unlikely(!pr))
                 return 0;
@@ -787,7 +787,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
         s64 idle_time_ns;
         s64 idle_time;
 
-        pr = __get_cpu_var(processors);
+        pr = __this_cpu_read(processors);
 
         if (unlikely(!pr))
                 return 0;
@@ -864,7 +864,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
         s64 idle_time;
 
 
-        pr = __get_cpu_var(processors);
+        pr = __this_cpu_read(processors);
 
         if (unlikely(!pr))
                 return 0;