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Merge branch 'nohz/printk-v8' into irq/core 

Conflicts:
	kernel/irq_work.c

Add support for printk in full dynticks CPU.

* Don't stop tick with irq works pending. This
fix is generally useful and concerns archs that
can't raise self IPIs.

* Flush irq works before CPU offlining.

* Introduce "lazy" irq works that can wait for the
next tick to be executed, unless it's stopped.

* Implement klogd wake up using irq work. This
removes the ad-hoc printk_tick()/printk_needs_cpu()
hooks and make it working even in dynticks mode.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2013-02-05 00:48:46 +01:00
parent f7c819c020 74876a98a8
commit 077931446b
8 changed files with 147 additions and 50 deletions
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20
include/linux/irq_work.h
View File

@ -3,6 +3,20 @@
#include <linux/llist.h>
/*
* An entry can be in one of four states:
*
* free NULL, 0 -> {claimed} : free to be used
* claimed NULL, 3 -> {pending} : claimed to be enqueued
* pending next, 3 -> {busy} : queued, pending callback
* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
*/
#define IRQ_WORK_PENDING 1UL
#define IRQ_WORK_BUSY 2UL
#define IRQ_WORK_FLAGS 3UL
#define IRQ_WORK_LAZY 4UL /* Doesn't want IPI, wait for tick */
struct irq_work {
unsigned long flags;
struct llist_node llnode;
@ -20,4 +34,10 @@ void irq_work_queue(struct irq_work *work);
void irq_work_run(void);
void irq_work_sync(struct irq_work *work);
#ifdef CONFIG_IRQ_WORK
bool irq_work_needs_cpu(void);
#else
static bool irq_work_needs_cpu(void) { return false; }
#endif
#endif /* _LINUX_IRQ_WORK_H */

3
include/linux/printk.h
View File

@ -98,9 +98,6 @@ int no_printk(const char *fmt, ...)
extern asmlinkage __printf(1, 2)
void early_printk(const char *fmt, ...);
extern int printk_needs_cpu(int cpu);
extern void printk_tick(void);
#ifdef CONFIG_PRINTK
asmlinkage __printf(5, 0)
int vprintk_emit(int facility, int level,

17
include/linux/tick.h
View File

@ -8,6 +8,8 @@
#include <linux/clockchips.h>
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#ifdef CONFIG_GENERIC_CLOCKEVENTS
@ -122,13 +124,26 @@ static inline int tick_oneshot_mode_active(void) { return 0; }
#endif /* !CONFIG_GENERIC_CLOCKEVENTS */
# ifdef CONFIG_NO_HZ
DECLARE_PER_CPU(struct tick_sched, tick_cpu_sched);
static inline int tick_nohz_tick_stopped(void)
{
return __this_cpu_read(tick_cpu_sched.tick_stopped);
}
extern void tick_nohz_idle_enter(void);
extern void tick_nohz_idle_exit(void);
extern void tick_nohz_irq_exit(void);
extern ktime_t tick_nohz_get_sleep_length(void);
extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
# else
# else /* !CONFIG_NO_HZ */
static inline int tick_nohz_tick_stopped(void)
{
return 0;
}
static inline void tick_nohz_idle_enter(void) { }
static inline void tick_nohz_idle_exit(void) { }

1
init/Kconfig
View File

@ -1259,6 +1259,7 @@ config HOTPLUG
config PRINTK
default y
bool "Enable support for printk" if EXPERT
select IRQ_WORK
help
This option enables normal printk support. Removing it
eliminates most of the message strings from the kernel image

112
kernel/irq_work.c
View File

@ -12,22 +12,15 @@
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <asm/processor.h>
/*
* An entry can be in one of four states:
*
* free NULL, 0 -> {claimed} : free to be used
* claimed NULL, 3 -> {pending} : claimed to be enqueued
* pending next, 3 -> {busy} : queued, pending callback
* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
*/
#define IRQ_WORK_PENDING 1UL
#define IRQ_WORK_BUSY 2UL
#define IRQ_WORK_FLAGS 3UL
static DEFINE_PER_CPU(struct llist_head, irq_work_list);
static DEFINE_PER_CPU(int, irq_work_raised);
/*
* Claim the entry so that no one else will poke at it.
@ -70,8 +63,6 @@ void __weak arch_irq_work_raise(void)
*/
void irq_work_queue(struct irq_work *work)
{
bool empty;
/* Only queue if not already pending */
if (!irq_work_claim(work))
return;
@ -79,30 +70,55 @@ void irq_work_queue(struct irq_work *work)
/* Queue the entry and raise the IPI if needed. */
preempt_disable();
empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
/* The list was empty, raise self-interrupt to start processing. */
if (empty)
arch_irq_work_raise();
llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
/*
* If the work is not "lazy" or the tick is stopped, raise the irq
* work interrupt (if supported by the arch), otherwise, just wait
* for the next tick.
*/
if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
arch_irq_work_raise();
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(irq_work_queue);
/*
* Run the irq_work entries on this cpu. Requires to be ran from hardirq
* context with local IRQs disabled.
*/
void irq_work_run(void)
bool irq_work_needs_cpu(void)
{
struct llist_head *this_list;
this_list = &__get_cpu_var(irq_work_list);
if (llist_empty(this_list))
return false;
/* All work should have been flushed before going offline */
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
return true;
}
static void __irq_work_run(void)
{
unsigned long flags;
struct irq_work *work;
struct llist_head *this_list;
struct llist_node *llnode;
/*
* Reset the "raised" state right before we check the list because
* an NMI may enqueue after we find the list empty from the runner.
*/
__this_cpu_write(irq_work_raised, 0);
barrier();
this_list = &__get_cpu_var(irq_work_list);
if (llist_empty(this_list))
return;
BUG_ON(!in_irq());
BUG_ON(!irqs_disabled());
llnode = llist_del_all(this_list);
@ -118,15 +134,27 @@ void irq_work_run(void)
* to claim that work don't rely on us to handle their data
* while we are in the middle of the func.
*/
xchg(&work->flags, IRQ_WORK_BUSY);
flags = work->flags & ~IRQ_WORK_PENDING;
xchg(&work->flags, flags);
work->func(work);
/*
* Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile.
*/
(void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
(void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
}
}
/*
* Run the irq_work entries on this cpu. Requires to be ran from hardirq
* context with local IRQs disabled.
*/
void irq_work_run(void)
{
BUG_ON(!in_irq());
__irq_work_run();
}
EXPORT_SYMBOL_GPL(irq_work_run);
/*
@ -141,3 +169,35 @@ void irq_work_sync(struct irq_work *work)
cpu_relax();
}
EXPORT_SYMBOL_GPL(irq_work_sync);
#ifdef CONFIG_HOTPLUG_CPU
static int irq_work_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
switch (action) {
case CPU_DYING:
/* Called from stop_machine */
if (WARN_ON_ONCE(cpu != smp_processor_id()))
break;
__irq_work_run();
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block cpu_notify;
static __init int irq_work_init_cpu_notifier(void)
{
cpu_notify.notifier_call = irq_work_cpu_notify;
cpu_notify.priority = 0;
register_cpu_notifier(&cpu_notify);
return 0;
}
device_initcall(irq_work_init_cpu_notifier);
#endif /* CONFIG_HOTPLUG_CPU */

36
kernel/printk.c
View File

@ -42,6 +42,7 @@
#include <linux/notifier.h>
#include <linux/rculist.h>
#include <linux/poll.h>
#include <linux/irq_work.h>
#include <asm/uaccess.h>
@ -1967,30 +1968,32 @@ int is_console_locked(void)
static DEFINE_PER_CPU(int, printk_pending);
static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
void printk_tick(void)
static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
if (__this_cpu_read(printk_pending)) {
int pending = __this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_SCHED) {
char *buf = __get_cpu_var(printk_sched_buf);
printk(KERN_WARNING "[sched_delayed] %s", buf);
}
if (pending & PRINTK_PENDING_WAKEUP)
wake_up_interruptible(&log_wait);
int pending = __this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_SCHED) {
char *buf = __get_cpu_var(printk_sched_buf);
printk(KERN_WARNING "[sched_delayed] %s", buf);
}
if (pending & PRINTK_PENDING_WAKEUP)
wake_up_interruptible(&log_wait);
}
int printk_needs_cpu(int cpu)
{
if (cpu_is_offline(cpu))
printk_tick();
return __this_cpu_read(printk_pending);
}
static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
.func = wake_up_klogd_work_func,
.flags = IRQ_WORK_LAZY,
};
void wake_up_klogd(void)
{
if (waitqueue_active(&log_wait))
preempt_disable();
if (waitqueue_active(&log_wait)) {
this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
}
preempt_enable();
}
static void console_cont_flush(char *text, size_t size)
@ -2471,6 +2474,7 @@ int printk_sched(const char *fmt, ...)
va_end(args);
__this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
local_irq_restore(flags);
return r;

7
kernel/time/tick-sched.c
View File

@ -20,6 +20,7 @@
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/irq_work.h>
#include <asm/irq_regs.h>
@ -28,7 +29,7 @@
/*
* Per cpu nohz control structure
*/
static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
/*
* The time, when the last jiffy update happened. Protected by jiffies_lock.
@ -331,8 +332,8 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
time_delta = timekeeping_max_deferment();
} while (read_seqretry(&jiffies_lock, seq));
if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
arch_needs_cpu(cpu)) {
if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
next_jiffies = last_jiffies + 1;
delta_jiffies = 1;
} else {

1
kernel/timer.c
View File

@ -1351,7 +1351,6 @@ void update_process_times(int user_tick)
account_process_tick(p, user_tick);
run_local_timers();
rcu_check_callbacks(cpu, user_tick);
printk_tick();
#ifdef CONFIG_IRQ_WORK
if (in_irq())
irq_work_run();