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

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__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>
This commit is contained in:
Christoph Lameter
2010-12-08 16:22:55 +01:00
committed by Tejun Heo
parent 780f36d8b3
commit 909ea96468
13 changed files with 60 additions and 66 deletions
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42
kernel/softirq.c
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@@ -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;
}