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SubjectRe: [Use cpuops V1 05/11] core: Replace __get_cpu_var with __this_cpu_read if not used for an address.
On Tue, 7 Dec 2010, Tejun Heo wrote:

> Can you please fold this into the original patch and resend? I
> skipped 04, 05 and 09. percpu#for-next now contains other patches.
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-next
>
> Thanks.

Subject: 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
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.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christoph Lameter <cl@linux.com>

---
include/asm-generic/irq_regs.h | 8 +++----
include/linux/elevator.h | 12 ++---------
include/linux/kernel_stat.h | 2 -
kernel/exit.c | 2 -
kernel/fork.c | 2 -
kernel/hrtimer.c | 2 -
kernel/printk.c | 4 +--
kernel/rcutree.c | 4 +--
kernel/softirq.c | 42 ++++++++++++++++++++---------------------
kernel/time/tick-common.c | 2 -
kernel/time/tick-oneshot.c | 4 +--
kernel/watchdog.c | 36 +++++++++++++++++------------------
mm/slab.c | 6 ++---
13 files changed, 60 insertions(+), 66 deletions(-)
Index: linux-2.6/mm/slab.c
===================================================================
--- linux-2.6.orig/mm/slab.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/mm/slab.c 2010-12-06 10:52:26.000000000 -0600
@@ -829,12 +829,12 @@ static void init_reap_node(int cpu)

static void next_reap_node(void)
{
- int node = __get_cpu_var(slab_reap_node);
+ int node = __this_cpu_read(slab_reap_node);

node = next_node(node, node_online_map);
if (unlikely(node >= MAX_NUMNODES))
node = first_node(node_online_map);
- __get_cpu_var(slab_reap_node) = node;
+ __this_cpu_write(slab_reap_node, node);
}

#else
@@ -1012,7 +1012,7 @@ static void __drain_alien_cache(struct k
*/
static void reap_alien(struct kmem_cache *cachep, struct kmem_list3 *l3)
{
- int node = __get_cpu_var(slab_reap_node);
+ int node = __this_cpu_read(slab_reap_node);

if (l3->alien) {
struct array_cache *ac = l3->alien[node];
Index: linux-2.6/kernel/rcutree.c
===================================================================
--- linux-2.6.orig/kernel/rcutree.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/rcutree.c 2010-12-06 10:52:26.000000000 -0600
@@ -367,8 +367,8 @@ void rcu_irq_exit(void)
WARN_ON_ONCE(rdtp->dynticks & 0x1);

/* If the interrupt queued a callback, get out of dyntick mode. */
- if (__get_cpu_var(rcu_sched_data).nxtlist ||
- __get_cpu_var(rcu_bh_data).nxtlist)
+ if (__this_cpu_read(rcu_sched_data.nxtlist) ||
+ __this_cpu_read(rcu_bh_data.nxtlist))
set_need_resched();
}

Index: linux-2.6/kernel/softirq.c
===================================================================
--- linux-2.6.orig/kernel/softirq.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/softirq.c 2010-12-07 08:49:32.000000000 -0600
@@ -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_s

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 taskle

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
{
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 softir
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 softir

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 sof
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 sof

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 i

/* 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;
}
Index: linux-2.6/kernel/time/tick-common.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-common.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/time/tick-common.c 2010-12-06 10:52:26.000000000 -0600
@@ -49,7 +49,7 @@ struct tick_device *tick_get_device(int
*/
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);
}
Index: linux-2.6/kernel/time/tick-oneshot.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-oneshot.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/time/tick-oneshot.c 2010-12-06 10:52:26.000000000 -0600
@@ -95,7 +95,7 @@ int tick_dev_program_event(struct clock_
*/
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;
Index: linux-2.6/kernel/watchdog.c
===================================================================
--- linux-2.6.orig/kernel/watchdog.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/watchdog.c 2010-12-06 10:52:26.000000000 -0600
@@ -116,12 +116,12 @@ static void __touch_watchdog(void)
{
int this_cpu = smp_processor_id();

- __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
+ __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
}

void touch_softlockup_watchdog(void)
{
- __raw_get_cpu_var(watchdog_touch_ts) = 0;
+ __this_cpu_write(watchdog_touch_ts, 0);
}
EXPORT_SYMBOL(touch_softlockup_watchdog);

@@ -165,12 +165,12 @@ void touch_softlockup_watchdog_sync(void
/* watchdog detector functions */
static int is_hardlockup(void)
{
- unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
+ unsigned long hrint = __this_cpu_read(hrtimer_interrupts);

- if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
+ if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
return 1;

- __get_cpu_var(hrtimer_interrupts_saved) = hrint;
+ __this_cpu_write(hrtimer_interrupts_saved, hrint);
return 0;
}
#endif
@@ -203,8 +203,8 @@ static void watchdog_overflow_callback(s
/* Ensure the watchdog never gets throttled */
event->hw.interrupts = 0;

- if (__get_cpu_var(watchdog_nmi_touch) == true) {
- __get_cpu_var(watchdog_nmi_touch) = false;
+ if (__this_cpu_read(watchdog_nmi_touch) == true) {
+ __this_cpu_write(watchdog_nmi_touch, false);
return;
}

@@ -218,7 +218,7 @@ static void watchdog_overflow_callback(s
int this_cpu = smp_processor_id();

/* only print hardlockups once */
- if (__get_cpu_var(hard_watchdog_warn) == true)
+ if (__this_cpu_read(hard_watchdog_warn) == true)
return;

if (hardlockup_panic)
@@ -226,16 +226,16 @@ static void watchdog_overflow_callback(s
else
WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);

- __get_cpu_var(hard_watchdog_warn) = true;
+ __this_cpu_write(hard_watchdog_warn, true);
return;
}

- __get_cpu_var(hard_watchdog_warn) = false;
+ __this_cpu_write(hard_watchdog_warn, false);
return;
}
static void watchdog_interrupt_count(void)
{
- __get_cpu_var(hrtimer_interrupts)++;
+ __this_cpu_inc(hrtimer_interrupts);
}
#else
static inline void watchdog_interrupt_count(void) { return; }
@@ -244,7 +244,7 @@ static inline void watchdog_interrupt_co
/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
- unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
+ unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
struct pt_regs *regs = get_irq_regs();
int duration;

@@ -252,18 +252,18 @@ static enum hrtimer_restart watchdog_tim
watchdog_interrupt_count();

/* kick the softlockup detector */
- wake_up_process(__get_cpu_var(softlockup_watchdog));
+ wake_up_process(__this_cpu_read(softlockup_watchdog));

/* .. and repeat */
hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));

if (touch_ts == 0) {
- if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
+ if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
/*
* If the time stamp was touched atomically
* make sure the scheduler tick is up to date.
*/
- __get_cpu_var(softlockup_touch_sync) = false;
+ __this_cpu_write(softlockup_touch_sync, false);
sched_clock_tick();
}
__touch_watchdog();
@@ -279,7 +279,7 @@ static enum hrtimer_restart watchdog_tim
duration = is_softlockup(touch_ts);
if (unlikely(duration)) {
/* only warn once */
- if (__get_cpu_var(soft_watchdog_warn) == true)
+ if (__this_cpu_read(soft_watchdog_warn) == true)
return HRTIMER_RESTART;

printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
@@ -294,9 +294,9 @@ static enum hrtimer_restart watchdog_tim

if (softlockup_panic)
panic("softlockup: hung tasks");
- __get_cpu_var(soft_watchdog_warn) = true;
+ __this_cpu_write(soft_watchdog_warn, true);
} else
- __get_cpu_var(soft_watchdog_warn) = false;
+ __this_cpu_write(soft_watchdog_warn, false);

return HRTIMER_RESTART;
}
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/printk.c 2010-12-06 10:52:26.000000000 -0600
@@ -1074,8 +1074,8 @@ static DEFINE_PER_CPU(int, printk_pendin

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);
}
}
Index: linux-2.6/include/asm-generic/irq_regs.h
===================================================================
--- linux-2.6.orig/include/asm-generic/irq_regs.h 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/include/asm-generic/irq_regs.h 2010-12-06 10:52:26.000000000 -0600
@@ -22,15 +22,15 @@ DECLARE_PER_CPU(struct pt_regs *, __irq_

static inline struct pt_regs *get_irq_regs(void)
{
- return __get_cpu_var(__irq_regs);
+ return __this_cpu_read(__irq_regs);
}

static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
{
- struct pt_regs *old_regs, **pp_regs = &__get_cpu_var(__irq_regs);
+ struct pt_regs *old_regs;

- old_regs = *pp_regs;
- *pp_regs = new_regs;
+ old_regs = __this_cpu_read(__irq_regs);
+ __this_cpu_write(__irq_regs, new_regs);
return old_regs;
}

Index: linux-2.6/include/linux/elevator.h
===================================================================
--- linux-2.6.orig/include/linux/elevator.h 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/include/linux/elevator.h 2010-12-06 10:52:26.000000000 -0600
@@ -195,15 +195,9 @@ enum {
/*
* io context count accounting
*/
-#define elv_ioc_count_mod(name, __val) \
- do { \
- preempt_disable(); \
- __get_cpu_var(name) += (__val); \
- preempt_enable(); \
- } while (0)
-
-#define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
-#define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
+#define elv_ioc_count_mod(name, __val) this_cpu_add(name, __val)
+#define elv_ioc_count_inc(name) this_cpu_inc(name)
+#define elv_ioc_count_dec(name) this_cpu_dec(name)

#define elv_ioc_count_read(name) \
({ \
Index: linux-2.6/include/linux/kernel_stat.h
===================================================================
--- linux-2.6.orig/include/linux/kernel_stat.h 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/include/linux/kernel_stat.h 2010-12-06 10:52:26.000000000 -0600
@@ -47,7 +47,7 @@ extern unsigned long long nr_context_swi

#ifndef CONFIG_GENERIC_HARDIRQS
#define kstat_irqs_this_cpu(irq) \
- (kstat_this_cpu.irqs[irq])
+ (this_cpu_read(kstat.irqs[irq])

struct irq_desc;

Index: linux-2.6/kernel/exit.c
===================================================================
--- linux-2.6.orig/kernel/exit.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/exit.c 2010-12-06 10:52:26.000000000 -0600
@@ -69,7 +69,7 @@ static void __unhash_process(struct task

list_del_rcu(&p->tasks);
list_del_init(&p->sibling);
- __get_cpu_var(process_counts)--;
+ __this_cpu_dec(process_counts);
}
list_del_rcu(&p->thread_group);
}
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/fork.c 2010-12-06 10:52:26.000000000 -0600
@@ -1282,7 +1282,7 @@ static struct task_struct *copy_process(
attach_pid(p, PIDTYPE_SID, task_session(current));
list_add_tail(&p->sibling, &p->real_parent->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
- __get_cpu_var(process_counts)++;
+ __this_cpu_inc(process_counts);
}
attach_pid(p, PIDTYPE_PID, pid);
nr_threads++;
Index: linux-2.6/kernel/hrtimer.c
===================================================================
--- linux-2.6.orig/kernel/hrtimer.c 2010-12-06 10:51:16.000000000 -0600
+++ linux-2.6/kernel/hrtimer.c 2010-12-06 10:52:26.000000000 -0600
@@ -497,7 +497,7 @@ static inline int hrtimer_is_hres_enable
*/
static inline int hrtimer_hres_active(void)
{
- return __get_cpu_var(hrtimer_bases).hres_active;
+ return __this_cpu_read(hrtimer_bases.hres_active);
}

/*

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