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, 21 insertions, 21 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 18f4be0d5fe0..d0a0dda52c1a 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -70,7 +70,7 @@ char *softirq_to_name[NR_SOFTIRQS] = {
 static void wakeup_softirqd(void)
 {
         /* Interrupts are disabled: no need to stop preemption */
-        struct task_struct *tsk = __get_cpu_var(ksoftirqd);
+        struct task_struct *tsk = __this_cpu_read(ksoftirqd);
 
         if (tsk && tsk->state != TASK_RUNNING)
                 wake_up_process(tsk);
@@ -388,8 +388,8 @@ void __tasklet_schedule(struct tasklet_struct *t)
 
         local_irq_save(flags);
         t->next = NULL;
-        *__get_cpu_var(tasklet_vec).tail = t;
-        __get_cpu_var(tasklet_vec).tail = &(t->next);
+        *__this_cpu_read(tasklet_vec.tail) = t;
+        __this_cpu_write(tasklet_vec.tail, &(t->next));
         raise_softirq_irqoff(TASKLET_SOFTIRQ);
         local_irq_restore(flags);
 }
@@ -402,8 +402,8 @@ void __tasklet_hi_schedule(struct tasklet_struct *t)
 
         local_irq_save(flags);
         t->next = NULL;
-        *__get_cpu_var(tasklet_hi_vec).tail = t;
-        __get_cpu_var(tasklet_hi_vec).tail = &(t->next);
+        *__this_cpu_read(tasklet_hi_vec.tail) = t;
+        __this_cpu_write(tasklet_hi_vec.tail,  &(t->next));
         raise_softirq_irqoff(HI_SOFTIRQ);
         local_irq_restore(flags);
 }
@@ -414,8 +414,8 @@ void __tasklet_hi_schedule_first(struct tasklet_struct *t)
 {
         BUG_ON(!irqs_disabled());
 
-        t->next = __get_cpu_var(tasklet_hi_vec).head;
-        __get_cpu_var(tasklet_hi_vec).head = t;
+        t->next = __this_cpu_read(tasklet_hi_vec.head);
+        __this_cpu_write(tasklet_hi_vec.head, t);
         __raise_softirq_irqoff(HI_SOFTIRQ);
 }
 
@@ -426,9 +426,9 @@ static void tasklet_action(struct softirq_action *a)
         struct tasklet_struct *list;
 
         local_irq_disable();
-        list = __get_cpu_var(tasklet_vec).head;
-        __get_cpu_var(tasklet_vec).head = NULL;
-        __get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head;
+        list = __this_cpu_read(tasklet_vec.head);
+        __this_cpu_write(tasklet_vec.head, NULL);
+        __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head);
         local_irq_enable();
 
         while (list) {
@@ -449,8 +449,8 @@ static void tasklet_action(struct softirq_action *a)
 
                 local_irq_disable();
                 t->next = NULL;
-                *__get_cpu_var(tasklet_vec).tail = t;
-                __get_cpu_var(tasklet_vec).tail = &(t->next);
+                *__this_cpu_read(tasklet_vec.tail) = t;
+                __this_cpu_write(tasklet_vec.tail, &(t->next));
                 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
                 local_irq_enable();
         }
@@ -461,9 +461,9 @@ static void tasklet_hi_action(struct softirq_action *a)
         struct tasklet_struct *list;
 
         local_irq_disable();
-        list = __get_cpu_var(tasklet_hi_vec).head;
-        __get_cpu_var(tasklet_hi_vec).head = NULL;
-        __get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head;
+        list = __this_cpu_read(tasklet_hi_vec.head);
+        __this_cpu_write(tasklet_hi_vec.head, NULL);
+        __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head);
         local_irq_enable();
 
         while (list) {
@@ -484,8 +484,8 @@ static void tasklet_hi_action(struct softirq_action *a)
 
                 local_irq_disable();
                 t->next = NULL;
-                *__get_cpu_var(tasklet_hi_vec).tail = t;
-                __get_cpu_var(tasklet_hi_vec).tail = &(t->next);
+                *__this_cpu_read(tasklet_hi_vec.tail) = t;
+                __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
                 __raise_softirq_irqoff(HI_SOFTIRQ);
                 local_irq_enable();
         }
@@ -802,16 +802,16 @@ static void takeover_tasklets(unsigned int cpu)
 
         /* Find end, append list for that CPU. */
         if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
-                *(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head;
-                __get_cpu_var(tasklet_vec).tail = per_cpu(tasklet_vec, cpu).tail;
+                *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
+                this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
                 per_cpu(tasklet_vec, cpu).head = NULL;
                 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
         }
         raise_softirq_irqoff(TASKLET_SOFTIRQ);
 
         if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
-                *__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head;
-                __get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).tail;
+                *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
+                __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
                 per_cpu(tasklet_hi_vec, cpu).head = NULL;
                 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
         }