[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / softirq.c

/*
 *	linux/kernel/softirq.c
 *
 *	Copyright (C) 1992 Linus Torvalds
 *
 *	Distribute under GPLv2.
 *
 *	Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
 */

#include <linux/module.h>
#include <linux/kernel_stat.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/notifier.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/rcupdate.h>
#include <linux/smp.h>
#include <linux/tick.h>

#include <asm/irq.h>
/*
   - No shared variables, all the data are CPU local.
   - If a softirq needs serialization, let it serialize itself
     by its own spinlocks.
   - Even if softirq is serialized, only local cpu is marked for
     execution. Hence, we get something sort of weak cpu binding.
     Though it is still not clear, will it result in better locality
     or will not.

   Examples:
   - NET RX softirq. It is multithreaded and does not require
     any global serialization.
   - NET TX softirq. It kicks software netdevice queues, hence
     it is logically serialized per device, but this serialization
     is invisible to common code.
   - Tasklets: serialized wrt itself.
 */

#ifndef __ARCH_IRQ_STAT
irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
EXPORT_SYMBOL(irq_stat);
#endif

static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp;

static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);

/*
 * we cannot loop indefinitely here to avoid userspace starvation,
 * but we also don't want to introduce a worst case 1/HZ latency
 * to the pending events, so lets the scheduler to balance
 * the softirq load for us.
 */
static inline void wakeup_softirqd(void)
{
	/* Interrupts are disabled: no need to stop preemption */
	struct task_struct *tsk = __get_cpu_var(ksoftirqd);

	if (tsk && tsk->state != TASK_RUNNING)
		wake_up_process(tsk);
}

/*
 * This one is for softirq.c-internal use,
 * where hardirqs are disabled legitimately:
 */
#ifdef CONFIG_TRACE_IRQFLAGS
static void __local_bh_disable(unsigned long ip)
{
	unsigned long flags;

	WARN_ON_ONCE(in_irq());

	raw_local_irq_save(flags);
	add_preempt_count(SOFTIRQ_OFFSET);
	/*
	 * Were softirqs turned off above:
	 */
	if (softirq_count() == SOFTIRQ_OFFSET)
		trace_softirqs_off(ip);
	raw_local_irq_restore(flags);
}
#else /* !CONFIG_TRACE_IRQFLAGS */
static inline void __local_bh_disable(unsigned long ip)
{
	add_preempt_count(SOFTIRQ_OFFSET);
	barrier();
}
#endif /* CONFIG_TRACE_IRQFLAGS */

void local_bh_disable(void)
{
	__local_bh_disable((unsigned long)__builtin_return_address(0));
}

EXPORT_SYMBOL(local_bh_disable);

void __local_bh_enable(void)
{
	WARN_ON_ONCE(in_irq());

	/*
	 * softirqs should never be enabled by __local_bh_enable(),
	 * it always nests inside local_bh_enable() sections:
	 */
	WARN_ON_ONCE(softirq_count() == SOFTIRQ_OFFSET);

	sub_preempt_count(SOFTIRQ_OFFSET);
}
EXPORT_SYMBOL_GPL(__local_bh_enable);

/*
 * Special-case - softirqs can safely be enabled in
 * cond_resched_softirq(), or by __do_softirq(),
 * without processing still-pending softirqs:
 */
void _local_bh_enable(void)
{
	WARN_ON_ONCE(in_irq());
	WARN_ON_ONCE(!irqs_disabled());

	if (softirq_count() == SOFTIRQ_OFFSET)
		trace_softirqs_on((unsigned long)__builtin_return_address(0));
	sub_preempt_count(SOFTIRQ_OFFSET);
}

EXPORT_SYMBOL(_local_bh_enable);

void local_bh_enable(void)
{
#ifdef CONFIG_TRACE_IRQFLAGS
	unsigned long flags;

	WARN_ON_ONCE(in_irq());
#endif
	WARN_ON_ONCE(irqs_disabled());

#ifdef CONFIG_TRACE_IRQFLAGS
	local_irq_save(flags);
#endif
	/*
	 * Are softirqs going to be turned on now:
	 */
	if (softirq_count() == SOFTIRQ_OFFSET)
		trace_softirqs_on((unsigned long)__builtin_return_address(0));
	/*
	 * Keep preemption disabled until we are done with
	 * softirq processing:
 	 */
 	sub_preempt_count(SOFTIRQ_OFFSET - 1);

	if (unlikely(!in_interrupt() && local_softirq_pending()))
		do_softirq();

	dec_preempt_count();
#ifdef CONFIG_TRACE_IRQFLAGS
	local_irq_restore(flags);
#endif
	preempt_check_resched();
}
EXPORT_SYMBOL(local_bh_enable);

void local_bh_enable_ip(unsigned long ip)
{
#ifdef CONFIG_TRACE_IRQFLAGS
	unsigned long flags;

	WARN_ON_ONCE(in_irq());

	local_irq_save(flags);
#endif
	/*
	 * Are softirqs going to be turned on now:
	 */
	if (softirq_count() == SOFTIRQ_OFFSET)
		trace_softirqs_on(ip);
	/*
	 * Keep preemption disabled until we are done with
	 * softirq processing:
 	 */
 	sub_preempt_count(SOFTIRQ_OFFSET - 1);

	if (unlikely(!in_interrupt() && local_softirq_pending()))
		do_softirq();

	dec_preempt_count();
#ifdef CONFIG_TRACE_IRQFLAGS
	local_irq_restore(flags);
#endif
	preempt_check_resched();
}
EXPORT_SYMBOL(local_bh_enable_ip);

/*
 * We restart softirq processing MAX_SOFTIRQ_RESTART times,
 * and we fall back to softirqd after that.
 *
 * This number has been established via experimentation.
 * The two things to balance is latency against fairness -
 * we want to handle softirqs as soon as possible, but they
 * should not be able to lock up the box.
 */
#define MAX_SOFTIRQ_RESTART 10

asmlinkage void __do_softirq(void)
{
	struct softirq_action *h;
	__u32 pending;
	int max_restart = MAX_SOFTIRQ_RESTART;
	int cpu;

	pending = local_softirq_pending();
	account_system_vtime(current);

	__local_bh_disable((unsigned long)__builtin_return_address(0));
	trace_softirq_enter();

	cpu = smp_processor_id();
restart:
	/* Reset the pending bitmask before enabling irqs */
	set_softirq_pending(0);

	local_irq_enable();

	h = softirq_vec;

	do {
		if (pending & 1) {
			h->action(h);
			rcu_bh_qsctr_inc(cpu);
		}
		h++;
		pending >>= 1;
	} while (pending);

	local_irq_disable();

	pending = local_softirq_pending();
	if (pending && --max_restart)
		goto restart;

	if (pending)
		wakeup_softirqd();

	trace_softirq_exit();

	account_system_vtime(current);
	_local_bh_enable();
}

#ifndef __ARCH_HAS_DO_SOFTIRQ

asmlinkage void do_softirq(void)
{
	__u32 pending;
	unsigned long flags;

	if (in_interrupt())
		return;

	local_irq_save(flags);

	pending = local_softirq_pending();

	if (pending)
		__do_softirq();

	local_irq_restore(flags);
}

#endif

/*
 * Enter an interrupt context.
 */
void irq_enter(void)
{
#ifdef CONFIG_NO_HZ
	int cpu = smp_processor_id();
	if (idle_cpu(cpu) && !in_interrupt())
		tick_nohz_stop_idle(cpu);
#endif
	__irq_enter();
#ifdef CONFIG_NO_HZ
	if (idle_cpu(cpu))
		tick_nohz_update_jiffies();
#endif
}

#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
# define invoke_softirq()	__do_softirq()
#else
# define invoke_softirq()	do_softirq()
#endif

/*
 * Exit an interrupt context. Process softirqs if needed and possible:
 */
void irq_exit(void)
{
	account_system_vtime(current);
	trace_hardirq_exit();
	sub_preempt_count(IRQ_EXIT_OFFSET);
	if (!in_interrupt() && local_softirq_pending())
		invoke_softirq();

#ifdef CONFIG_NO_HZ
	/* Make sure that timer wheel updates are propagated */
	if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
		tick_nohz_stop_sched_tick();
	rcu_irq_exit();
#endif
	preempt_enable_no_resched();
}

/*
 * This function must run with irqs disabled!
 */
inline void raise_softirq_irqoff(unsigned int nr)
{
	__raise_softirq_irqoff(nr);

	/*
	 * If we're in an interrupt or softirq, we're done
	 * (this also catches softirq-disabled code). We will
	 * actually run the softirq once we return from
	 * the irq or softirq.
	 *
	 * Otherwise we wake up ksoftirqd to make sure we
	 * schedule the softirq soon.
	 */
	if (!in_interrupt())
		wakeup_softirqd();
}

void raise_softirq(unsigned int nr)
{
	unsigned long flags;

	local_irq_save(flags);
	raise_softirq_irqoff(nr);
	local_irq_restore(flags);
}

void open_softirq(int nr, void (*action)(struct softirq_action *))
{
	softirq_vec[nr].action = action;
}

/* Tasklets */
struct tasklet_head
{
	struct tasklet_struct *head;
	struct tasklet_struct **tail;
};

static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);

void __tasklet_schedule(struct tasklet_struct *t)
{
	unsigned long flags;

	local_irq_save(flags);
	t->next = NULL;
	*__get_cpu_var(tasklet_vec).tail = t;
	__get_cpu_var(tasklet_vec).tail = &(t->next);
	raise_softirq_irqoff(TASKLET_SOFTIRQ);
	local_irq_restore(flags);
}

EXPORT_SYMBOL(__tasklet_schedule);

void __tasklet_hi_schedule(struct tasklet_struct *t)
{
	unsigned long flags;

	local_irq_save(flags);
	t->next = NULL;
	*__get_cpu_var(tasklet_hi_vec).tail = t;
	__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
	raise_softirq_irqoff(HI_SOFTIRQ);
	local_irq_restore(flags);
}

EXPORT_SYMBOL(__tasklet_hi_schedule);

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;
	local_irq_enable();

	while (list) {
		struct tasklet_struct *t = list;

		list = list->next;

		if (tasklet_trylock(t)) {
			if (!atomic_read(&t->count)) {
				if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
					BUG();
				t->func(t->data);
				tasklet_unlock(t);
				continue;
			}
			tasklet_unlock(t);
		}

		local_irq_disable();
		t->next = NULL;
		*__get_cpu_var(tasklet_vec).tail = t;
		__get_cpu_var(tasklet_vec).tail = &(t->next);
		__raise_softirq_irqoff(TASKLET_SOFTIRQ);
		local_irq_enable();
	}
}

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;
	local_irq_enable();

	while (list) {
		struct tasklet_struct *t = list;

		list = list->next;

		if (tasklet_trylock(t)) {
			if (!atomic_read(&t->count)) {
				if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
					BUG();
				t->func(t->data);
				tasklet_unlock(t);
				continue;
			}
			tasklet_unlock(t);
		}

		local_irq_disable();
		t->next = NULL;
		*__get_cpu_var(tasklet_hi_vec).tail = t;
		__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
		__raise_softirq_irqoff(HI_SOFTIRQ);
		local_irq_enable();
	}
}


void tasklet_init(struct tasklet_struct *t,
		  void (*func)(unsigned long), unsigned long data)
{
	t->next = NULL;
	t->state = 0;
	atomic_set(&t->count, 0);
	t->func = func;
	t->data = data;
}

EXPORT_SYMBOL(tasklet_init);

void tasklet_kill(struct tasklet_struct *t)
{
	if (in_interrupt())
		printk("Attempt to kill tasklet from interrupt\n");

	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
		do
			yield();
		while (test_bit(TASKLET_STATE_SCHED, &t->state));
	}
	tasklet_unlock_wait(t);
	clear_bit(TASKLET_STATE_SCHED, &t->state);
}

EXPORT_SYMBOL(tasklet_kill);

void __init softirq_init(void)
{
	int cpu;

	for_each_possible_cpu(cpu) {
		per_cpu(tasklet_vec, cpu).tail =
			&per_cpu(tasklet_vec, cpu).head;
		per_cpu(tasklet_hi_vec, cpu).tail =
			&per_cpu(tasklet_hi_vec, cpu).head;
	}

	open_softirq(TASKLET_SOFTIRQ, tasklet_action);
	open_softirq(HI_SOFTIRQ, tasklet_hi_action);
}

static int ksoftirqd(void * __bind_cpu)
{
	set_current_state(TASK_INTERRUPTIBLE);

	while (!kthread_should_stop()) {
		preempt_disable();
		if (!local_softirq_pending()) {
			preempt_enable_no_resched();
			schedule();
			preempt_disable();
		}

		__set_current_state(TASK_RUNNING);

		while (local_softirq_pending()) {
			/* Preempt disable stops cpu going offline.
			   If already offline, we'll be on wrong CPU:
			   don't process */
			if (cpu_is_offline((long)__bind_cpu))
				goto wait_to_die;
			do_softirq();
			preempt_enable_no_resched();
			cond_resched();
			preempt_disable();
		}
		preempt_enable();
		set_current_state(TASK_INTERRUPTIBLE);
	}
	__set_current_state(TASK_RUNNING);
	return 0;

wait_to_die:
	preempt_enable();
	/* Wait for kthread_stop */
	set_current_state(TASK_INTERRUPTIBLE);
	while (!kthread_should_stop()) {
		schedule();
		set_current_state(TASK_INTERRUPTIBLE);
	}
	__set_current_state(TASK_RUNNING);
	return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
/*
 * tasklet_kill_immediate is called to remove a tasklet which can already be
 * scheduled for execution on @cpu.
 *
 * Unlike tasklet_kill, this function removes the tasklet
 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
 *
 * When this function is called, @cpu must be in the CPU_DEAD state.
 */
void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
{
	struct tasklet_struct **i;

	BUG_ON(cpu_online(cpu));
	BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));

	if (!test_bit(TASKLET_STATE_SCHED, &t->state))
		return;

	/* CPU is dead, so no lock needed. */
	for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
		if (*i == t) {
			*i = t->next;
			/* If this was the tail element, move the tail ptr */
			if (*i == NULL)
				per_cpu(tasklet_vec, cpu).tail = i;
			return;
		}
	}
	BUG();
}

static void takeover_tasklets(unsigned int cpu)
{
	/* CPU is dead, so no lock needed. */
	local_irq_disable();

	/* 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;
		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;
		per_cpu(tasklet_hi_vec, cpu).head = NULL;
		per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
	}
	raise_softirq_irqoff(HI_SOFTIRQ);

	local_irq_enable();
}
#endif /* CONFIG_HOTPLUG_CPU */

static int __cpuinit cpu_callback(struct notifier_block *nfb,
				  unsigned long action,
				  void *hcpu)
{
	int hotcpu = (unsigned long)hcpu;
	struct task_struct *p;

	switch (action) {
	case CPU_UP_PREPARE:
	case CPU_UP_PREPARE_FROZEN:
		p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);
		if (IS_ERR(p)) {
			printk("ksoftirqd for %i failed\n", hotcpu);
			return NOTIFY_BAD;
		}
		kthread_bind(p, hotcpu);
  		per_cpu(ksoftirqd, hotcpu) = p;
 		break;
	case CPU_ONLINE:
	case CPU_ONLINE_FROZEN:
		wake_up_process(per_cpu(ksoftirqd, hotcpu));
		break;
#ifdef CONFIG_HOTPLUG_CPU
	case CPU_UP_CANCELED:
	case CPU_UP_CANCELED_FROZEN:
		if (!per_cpu(ksoftirqd, hotcpu))
			break;
		/* Unbind so it can run.  Fall thru. */
		kthread_bind(per_cpu(ksoftirqd, hotcpu),
			     any_online_cpu(cpu_online_map));
	case CPU_DEAD:
	case CPU_DEAD_FROZEN: {
		struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

		p = per_cpu(ksoftirqd, hotcpu);
		per_cpu(ksoftirqd, hotcpu) = NULL;
		sched_setscheduler(p, SCHED_FIFO, &param);
		kthread_stop(p);
		takeover_tasklets(hotcpu);
		break;
	}
#endif /* CONFIG_HOTPLUG_CPU */
 	}
	return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata cpu_nfb = {
	.notifier_call = cpu_callback
};

__init int spawn_ksoftirqd(void)
{
	void *cpu = (void *)(long)smp_processor_id();
	int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);

	BUG_ON(err == NOTIFY_BAD);
	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
	register_cpu_notifier(&cpu_nfb);
	return 0;
}

#ifdef CONFIG_SMP
/*
 * Call a function on all processors
 */
int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait)
{
	int ret = 0;

	preempt_disable();
	ret = smp_call_function(func, info, retry, wait);
	local_irq_disable();
	func(info);
	local_irq_enable();
	preempt_enable();
	return ret;
}
EXPORT_SYMBOL(on_each_cpu);
#endif
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/kernel/softirq.c
	3	*
	4	* Copyright (C) 1992 Linus Torvalds
	5	*
b10db7f0 PM	6	* Distribute under GPLv2.
	7	*
	8	* Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
1da177e4 LT	9	*/
	10
	11	#include <linux/module.h>
	12	#include <linux/kernel_stat.h>
	13	#include <linux/interrupt.h>
	14	#include <linux/init.h>
	15	#include <linux/mm.h>
	16	#include <linux/notifier.h>
	17	#include <linux/percpu.h>
	18	#include <linux/cpu.h>
83144186	19	#include <linux/freezer.h>
1da177e4 LT	20	#include <linux/kthread.h>
1da177e4 LT	21	#include <linux/rcupdate.h>
78eef01b	22	#include <linux/smp.h>
79bf2bb3	23	#include <linux/tick.h>
1da177e4 LT	24
	25	#include <asm/irq.h>
	26	/*
	27	- No shared variables, all the data are CPU local.
	28	- If a softirq needs serialization, let it serialize itself
	29	by its own spinlocks.
	30	- Even if softirq is serialized, only local cpu is marked for
	31	execution. Hence, we get something sort of weak cpu binding.
	32	Though it is still not clear, will it result in better locality
	33	or will not.
	34
	35	Examples:
	36	- NET RX softirq. It is multithreaded and does not require
	37	any global serialization.
	38	- NET TX softirq. It kicks software netdevice queues, hence
	39	it is logically serialized per device, but this serialization
	40	is invisible to common code.
	41	- Tasklets: serialized wrt itself.
	42	*/
	43
	44	#ifndef __ARCH_IRQ_STAT
	45	irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
	46	EXPORT_SYMBOL(irq_stat);
	47	#endif
	48
	49	static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp;
	50
	51	static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
	52
	53	/*
	54	* we cannot loop indefinitely here to avoid userspace starvation,
	55	* but we also don't want to introduce a worst case 1/HZ latency
	56	* to the pending events, so lets the scheduler to balance
	57	* the softirq load for us.
	58	*/
	59	static inline void wakeup_softirqd(void)
	60	{
	61	/* Interrupts are disabled: no need to stop preemption */
	62	struct task_struct *tsk = __get_cpu_var(ksoftirqd);
	63
	64	if (tsk && tsk->state != TASK_RUNNING)
	65	wake_up_process(tsk);
	66	}
	67
de30a2b3 IM	68	/*
	69	* This one is for softirq.c-internal use,
	70	* where hardirqs are disabled legitimately:
	71	*/
3c829c36	72	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3 IM	73	static void __local_bh_disable(unsigned long ip)
	74	{
	75	unsigned long flags;
	76
	77	WARN_ON_ONCE(in_irq());
	78
	79	raw_local_irq_save(flags);
	80	add_preempt_count(SOFTIRQ_OFFSET);
	81	/*
	82	* Were softirqs turned off above:
	83	*/
	84	if (softirq_count() == SOFTIRQ_OFFSET)
	85	trace_softirqs_off(ip);
	86	raw_local_irq_restore(flags);
	87	}
3c829c36 TC	88	#else /* !CONFIG_TRACE_IRQFLAGS */
	89	static inline void __local_bh_disable(unsigned long ip)
	90	{
	91	add_preempt_count(SOFTIRQ_OFFSET);
	92	barrier();
	93	}
	94	#endif /* CONFIG_TRACE_IRQFLAGS */
de30a2b3 IM	95
	96	void local_bh_disable(void)
	97	{
	98	__local_bh_disable((unsigned long)__builtin_return_address(0));
	99	}
	100
	101	EXPORT_SYMBOL(local_bh_disable);
	102
	103	void __local_bh_enable(void)
	104	{
	105	WARN_ON_ONCE(in_irq());
	106
	107	/*
	108	* softirqs should never be enabled by __local_bh_enable(),
	109	* it always nests inside local_bh_enable() sections:
	110	*/
	111	WARN_ON_ONCE(softirq_count() == SOFTIRQ_OFFSET);
	112
	113	sub_preempt_count(SOFTIRQ_OFFSET);
	114	}
	115	EXPORT_SYMBOL_GPL(__local_bh_enable);
	116
	117	/*
	118	* Special-case - softirqs can safely be enabled in
	119	* cond_resched_softirq(), or by __do_softirq(),
	120	* without processing still-pending softirqs:
	121	*/
	122	void _local_bh_enable(void)
	123	{
	124	WARN_ON_ONCE(in_irq());
	125	WARN_ON_ONCE(!irqs_disabled());
	126
	127	if (softirq_count() == SOFTIRQ_OFFSET)
	128	trace_softirqs_on((unsigned long)__builtin_return_address(0));
	129	sub_preempt_count(SOFTIRQ_OFFSET);
	130	}
	131
	132	EXPORT_SYMBOL(_local_bh_enable);
	133
	134	void local_bh_enable(void)
	135	{
3c829c36	136	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3 IM	137	unsigned long flags;
	138
	139	WARN_ON_ONCE(in_irq());
3c829c36	140	#endif
de30a2b3 IM	141	WARN_ON_ONCE(irqs_disabled());
de30a2b3 IM	142
3c829c36	143	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3	144	local_irq_save(flags);
3c829c36	145	#endif
de30a2b3 IM	146	/*
	147	* Are softirqs going to be turned on now:
	148	*/
	149	if (softirq_count() == SOFTIRQ_OFFSET)
	150	trace_softirqs_on((unsigned long)__builtin_return_address(0));
	151	/*
	152	* Keep preemption disabled until we are done with
	153	* softirq processing:
	154	*/
	155	sub_preempt_count(SOFTIRQ_OFFSET - 1);
	156
	157	if (unlikely(!in_interrupt() && local_softirq_pending()))
	158	do_softirq();
	159
	160	dec_preempt_count();
3c829c36	161	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3	162	local_irq_restore(flags);
3c829c36	163	#endif
de30a2b3 IM	164	preempt_check_resched();
	165	}
	166	EXPORT_SYMBOL(local_bh_enable);
	167
	168	void local_bh_enable_ip(unsigned long ip)
	169	{
3c829c36	170	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3 IM	171	unsigned long flags;
	172
	173	WARN_ON_ONCE(in_irq());
	174
	175	local_irq_save(flags);
3c829c36	176	#endif
de30a2b3 IM	177	/*
	178	* Are softirqs going to be turned on now:
	179	*/
	180	if (softirq_count() == SOFTIRQ_OFFSET)
	181	trace_softirqs_on(ip);
	182	/*
	183	* Keep preemption disabled until we are done with
	184	* softirq processing:
	185	*/
	186	sub_preempt_count(SOFTIRQ_OFFSET - 1);
	187
	188	if (unlikely(!in_interrupt() && local_softirq_pending()))
	189	do_softirq();
	190
	191	dec_preempt_count();
3c829c36	192	#ifdef CONFIG_TRACE_IRQFLAGS
de30a2b3	193	local_irq_restore(flags);
3c829c36	194	#endif
de30a2b3 IM	195	preempt_check_resched();
	196	}
	197	EXPORT_SYMBOL(local_bh_enable_ip);
	198
1da177e4 LT	199	/*
	200	* We restart softirq processing MAX_SOFTIRQ_RESTART times,
	201	* and we fall back to softirqd after that.
	202	*
	203	* This number has been established via experimentation.
	204	* The two things to balance is latency against fairness -
	205	* we want to handle softirqs as soon as possible, but they
	206	* should not be able to lock up the box.
	207	*/
	208	#define MAX_SOFTIRQ_RESTART 10
	209
	210	asmlinkage void __do_softirq(void)
	211	{
	212	struct softirq_action *h;
	213	__u32 pending;
	214	int max_restart = MAX_SOFTIRQ_RESTART;
	215	int cpu;
	216
	217	pending = local_softirq_pending();
829035fd PM	218	account_system_vtime(current);
829035fd PM	219
de30a2b3 IM	220	__local_bh_disable((unsigned long)__builtin_return_address(0));
de30a2b3 IM	221	trace_softirq_enter();
1da177e4	222
1da177e4 LT	223	cpu = smp_processor_id();
	224	restart:
	225	/* Reset the pending bitmask before enabling irqs */
3f74478b	226	set_softirq_pending(0);
1da177e4	227
c70f5d66	228	local_irq_enable();
1da177e4 LT	229
	230	h = softirq_vec;
	231
	232	do {
	233	if (pending & 1) {
	234	h->action(h);
	235	rcu_bh_qsctr_inc(cpu);
	236	}
	237	h++;
	238	pending >>= 1;
	239	} while (pending);
	240
c70f5d66	241	local_irq_disable();
1da177e4 LT	242
	243	pending = local_softirq_pending();
	244	if (pending && --max_restart)
	245	goto restart;
	246
	247	if (pending)
	248	wakeup_softirqd();
	249
de30a2b3	250	trace_softirq_exit();
829035fd PM	251
829035fd PM	252	account_system_vtime(current);
de30a2b3	253	_local_bh_enable();
1da177e4 LT	254	}
	255
	256	#ifndef __ARCH_HAS_DO_SOFTIRQ
	257
	258	asmlinkage void do_softirq(void)
	259	{
	260	__u32 pending;
	261	unsigned long flags;
	262
	263	if (in_interrupt())
	264	return;
	265
	266	local_irq_save(flags);
	267
	268	pending = local_softirq_pending();
	269
	270	if (pending)
	271	__do_softirq();
	272
	273	local_irq_restore(flags);
	274	}
	275
1da177e4 LT	276	#endif
1da177e4 LT	277
dde4b2b5 IM	278	/*
	279	* Enter an interrupt context.
	280	*/
	281	void irq_enter(void)
	282	{
6378ddb5 VP	283	#ifdef CONFIG_NO_HZ
	284	int cpu = smp_processor_id();
	285	if (idle_cpu(cpu) && !in_interrupt())
	286	tick_nohz_stop_idle(cpu);
	287	#endif
79bf2bb3 TG	288	__irq_enter();
79bf2bb3 TG	289	#ifdef CONFIG_NO_HZ
6378ddb5	290	if (idle_cpu(cpu))
79bf2bb3 TG	291	tick_nohz_update_jiffies();
79bf2bb3 TG	292	#endif
dde4b2b5 IM	293	}
dde4b2b5 IM	294
1da177e4 LT	295	#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
	296	# define invoke_softirq() __do_softirq()
	297	#else
	298	# define invoke_softirq() do_softirq()
	299	#endif
	300
	301	/*
	302	* Exit an interrupt context. Process softirqs if needed and possible:
	303	*/
	304	void irq_exit(void)
	305	{
	306	account_system_vtime(current);
de30a2b3	307	trace_hardirq_exit();
1da177e4 LT	308	sub_preempt_count(IRQ_EXIT_OFFSET);
	309	if (!in_interrupt() && local_softirq_pending())
	310	invoke_softirq();
79bf2bb3 TG	311
	312	#ifdef CONFIG_NO_HZ
	313	/* Make sure that timer wheel updates are propagated */
	314	if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
	315	tick_nohz_stop_sched_tick();
2232c2d8	316	rcu_irq_exit();
79bf2bb3	317	#endif
1da177e4 LT	318	preempt_enable_no_resched();
	319	}
	320
	321	/*
	322	* This function must run with irqs disabled!
	323	*/
7ad5b3a5	324	inline void raise_softirq_irqoff(unsigned int nr)
1da177e4 LT	325	{
	326	__raise_softirq_irqoff(nr);
	327
	328	/*
	329	* If we're in an interrupt or softirq, we're done
	330	* (this also catches softirq-disabled code). We will
	331	* actually run the softirq once we return from
	332	* the irq or softirq.
	333	*
	334	* Otherwise we wake up ksoftirqd to make sure we
	335	* schedule the softirq soon.
	336	*/
	337	if (!in_interrupt())
	338	wakeup_softirqd();
	339	}
	340
7ad5b3a5	341	void raise_softirq(unsigned int nr)
1da177e4 LT	342	{
	343	unsigned long flags;
	344
	345	local_irq_save(flags);
	346	raise_softirq_irqoff(nr);
	347	local_irq_restore(flags);
	348	}
	349
962cf36c	350	void open_softirq(int nr, void (action)(struct softirq_action ))
1da177e4	351	{
1da177e4 LT	352	softirq_vec[nr].action = action;
	353	}
	354
1da177e4 LT	355	/* Tasklets */
	356	struct tasklet_head
	357	{
48f20a9a OJ	358	struct tasklet_struct *head;
48f20a9a OJ	359	struct tasklet_struct **tail;
1da177e4 LT	360	};
1da177e4 LT	361
4620b49f VN	362	static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
4620b49f VN	363	static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
1da177e4	364
7ad5b3a5	365	void __tasklet_schedule(struct tasklet_struct *t)
1da177e4 LT	366	{
	367	unsigned long flags;
	368
	369	local_irq_save(flags);
48f20a9a OJ	370	t->next = NULL;
	371	*__get_cpu_var(tasklet_vec).tail = t;
	372	__get_cpu_var(tasklet_vec).tail = &(t->next);
1da177e4 LT	373	raise_softirq_irqoff(TASKLET_SOFTIRQ);
	374	local_irq_restore(flags);
	375	}
	376
	377	EXPORT_SYMBOL(__tasklet_schedule);
	378
7ad5b3a5	379	void __tasklet_hi_schedule(struct tasklet_struct *t)
1da177e4 LT	380	{
	381	unsigned long flags;
	382
	383	local_irq_save(flags);
48f20a9a OJ	384	t->next = NULL;
	385	*__get_cpu_var(tasklet_hi_vec).tail = t;
	386	__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
1da177e4 LT	387	raise_softirq_irqoff(HI_SOFTIRQ);
	388	local_irq_restore(flags);
	389	}
	390
	391	EXPORT_SYMBOL(__tasklet_hi_schedule);
	392
	393	static void tasklet_action(struct softirq_action *a)
	394	{
	395	struct tasklet_struct *list;
	396
	397	local_irq_disable();
48f20a9a OJ	398	list = __get_cpu_var(tasklet_vec).head;
	399	__get_cpu_var(tasklet_vec).head = NULL;
	400	__get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head;
1da177e4 LT	401	local_irq_enable();
	402
	403	while (list) {
	404	struct tasklet_struct *t = list;
	405
	406	list = list->next;
	407
	408	if (tasklet_trylock(t)) {
	409	if (!atomic_read(&t->count)) {
	410	if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
	411	BUG();
	412	t->func(t->data);
	413	tasklet_unlock(t);
	414	continue;
	415	}
	416	tasklet_unlock(t);
	417	}
	418
	419	local_irq_disable();
48f20a9a OJ	420	t->next = NULL;
	421	*__get_cpu_var(tasklet_vec).tail = t;
	422	__get_cpu_var(tasklet_vec).tail = &(t->next);
1da177e4 LT	423	__raise_softirq_irqoff(TASKLET_SOFTIRQ);
	424	local_irq_enable();
	425	}
	426	}
	427
	428	static void tasklet_hi_action(struct softirq_action *a)
	429	{
	430	struct tasklet_struct *list;
	431
	432	local_irq_disable();
48f20a9a OJ	433	list = __get_cpu_var(tasklet_hi_vec).head;
	434	__get_cpu_var(tasklet_hi_vec).head = NULL;
	435	__get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head;
1da177e4 LT	436	local_irq_enable();
	437
	438	while (list) {
	439	struct tasklet_struct *t = list;
	440
	441	list = list->next;
	442
	443	if (tasklet_trylock(t)) {
	444	if (!atomic_read(&t->count)) {
	445	if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
	446	BUG();
	447	t->func(t->data);
	448	tasklet_unlock(t);
	449	continue;
	450	}
	451	tasklet_unlock(t);
	452	}
	453
	454	local_irq_disable();
48f20a9a OJ	455	t->next = NULL;
	456	*__get_cpu_var(tasklet_hi_vec).tail = t;
	457	__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
1da177e4 LT	458	__raise_softirq_irqoff(HI_SOFTIRQ);
	459	local_irq_enable();
	460	}
	461	}
	462
	463
	464	void tasklet_init(struct tasklet_struct *t,
	465	void (*func)(unsigned long), unsigned long data)
	466	{
	467	t->next = NULL;
	468	t->state = 0;
	469	atomic_set(&t->count, 0);
	470	t->func = func;
	471	t->data = data;
	472	}
	473
	474	EXPORT_SYMBOL(tasklet_init);
	475
	476	void tasklet_kill(struct tasklet_struct *t)
	477	{
	478	if (in_interrupt())
	479	printk("Attempt to kill tasklet from interrupt\n");
	480
	481	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
	482	do
	483	yield();
	484	while (test_bit(TASKLET_STATE_SCHED, &t->state));
	485	}
	486	tasklet_unlock_wait(t);
	487	clear_bit(TASKLET_STATE_SCHED, &t->state);
	488	}
	489
	490	EXPORT_SYMBOL(tasklet_kill);
	491
	492	void __init softirq_init(void)
	493	{
48f20a9a OJ	494	int cpu;
	495
	496	for_each_possible_cpu(cpu) {
	497	per_cpu(tasklet_vec, cpu).tail =
	498	&per_cpu(tasklet_vec, cpu).head;
	499	per_cpu(tasklet_hi_vec, cpu).tail =
	500	&per_cpu(tasklet_hi_vec, cpu).head;
	501	}
	502
962cf36c CM	503	open_softirq(TASKLET_SOFTIRQ, tasklet_action);
962cf36c CM	504	open_softirq(HI_SOFTIRQ, tasklet_hi_action);
1da177e4 LT	505	}
	506
	507	static int ksoftirqd(void * __bind_cpu)
	508	{
1da177e4 LT	509	set_current_state(TASK_INTERRUPTIBLE);
	510
	511	while (!kthread_should_stop()) {
	512	preempt_disable();
	513	if (!local_softirq_pending()) {
	514	preempt_enable_no_resched();
	515	schedule();
	516	preempt_disable();
	517	}
	518
	519	__set_current_state(TASK_RUNNING);
	520
	521	while (local_softirq_pending()) {
	522	/* Preempt disable stops cpu going offline.
	523	If already offline, we'll be on wrong CPU:
	524	don't process */
	525	if (cpu_is_offline((long)__bind_cpu))
	526	goto wait_to_die;
	527	do_softirq();
	528	preempt_enable_no_resched();
	529	cond_resched();
	530	preempt_disable();
	531	}
	532	preempt_enable();
	533	set_current_state(TASK_INTERRUPTIBLE);
	534	}
	535	__set_current_state(TASK_RUNNING);
	536	return 0;
	537
	538	wait_to_die:
	539	preempt_enable();
	540	/* Wait for kthread_stop */
	541	set_current_state(TASK_INTERRUPTIBLE);
	542	while (!kthread_should_stop()) {
	543	schedule();
	544	set_current_state(TASK_INTERRUPTIBLE);
	545	}
	546	__set_current_state(TASK_RUNNING);
	547	return 0;
	548	}
	549
	550	#ifdef CONFIG_HOTPLUG_CPU
	551	/*
	552	* tasklet_kill_immediate is called to remove a tasklet which can already be
	553	* scheduled for execution on @cpu.
	554	*
	555	* Unlike tasklet_kill, this function removes the tasklet
	556	* _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
	557	*
	558	* When this function is called, @cpu must be in the CPU_DEAD state.
	559	*/
	560	void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
	561	{
	562	struct tasklet_struct **i;
	563
	564	BUG_ON(cpu_online(cpu));
	565	BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
	566
	567	if (!test_bit(TASKLET_STATE_SCHED, &t->state))
	568	return;
	569
	570	/* CPU is dead, so no lock needed. */
48f20a9a	571	for (i = &per_cpu(tasklet_vec, cpu).head; i; i = &(i)->next) {
1da177e4 LT	572	if (*i == t) {
1da177e4 LT	573	*i = t->next;
48f20a9a OJ	574	/* If this was the tail element, move the tail ptr */
	575	if (*i == NULL)
	576	per_cpu(tasklet_vec, cpu).tail = i;
1da177e4 LT	577	return;
	578	}
	579	}
	580	BUG();
	581	}
	582
	583	static void takeover_tasklets(unsigned int cpu)
	584	{
1da177e4 LT	585	/* CPU is dead, so no lock needed. */
	586	local_irq_disable();
	587
	588	/* Find end, append list for that CPU. */
e5e41723 CB	589	if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
	590	*(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head;
	591	__get_cpu_var(tasklet_vec).tail = per_cpu(tasklet_vec, cpu).tail;
	592	per_cpu(tasklet_vec, cpu).head = NULL;
	593	per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
	594	}
1da177e4 LT	595	raise_softirq_irqoff(TASKLET_SOFTIRQ);
1da177e4 LT	596
e5e41723 CB	597	if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
	598	*__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head;
	599	__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).tail;
	600	per_cpu(tasklet_hi_vec, cpu).head = NULL;
	601	per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
	602	}
1da177e4 LT	603	raise_softirq_irqoff(HI_SOFTIRQ);
	604
	605	local_irq_enable();
	606	}
	607	#endif /* CONFIG_HOTPLUG_CPU */
	608
8c78f307	609	static int __cpuinit cpu_callback(struct notifier_block *nfb,
1da177e4 LT	610	unsigned long action,
	611	void *hcpu)
	612	{
	613	int hotcpu = (unsigned long)hcpu;
	614	struct task_struct *p;
	615
	616	switch (action) {
	617	case CPU_UP_PREPARE:
8bb78442	618	case CPU_UP_PREPARE_FROZEN:
1da177e4 LT	619	p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);
	620	if (IS_ERR(p)) {
	621	printk("ksoftirqd for %i failed\n", hotcpu);
	622	return NOTIFY_BAD;
	623	}
	624	kthread_bind(p, hotcpu);
	625	per_cpu(ksoftirqd, hotcpu) = p;
	626	break;
	627	case CPU_ONLINE:
8bb78442	628	case CPU_ONLINE_FROZEN:
1da177e4 LT	629	wake_up_process(per_cpu(ksoftirqd, hotcpu));
	630	break;
	631	#ifdef CONFIG_HOTPLUG_CPU
	632	case CPU_UP_CANCELED:
8bb78442	633	case CPU_UP_CANCELED_FROZEN:
fc75cdfa HC	634	if (!per_cpu(ksoftirqd, hotcpu))
fc75cdfa HC	635	break;
1da177e4	636	/* Unbind so it can run. Fall thru. */
a4c4af7c HC	637	kthread_bind(per_cpu(ksoftirqd, hotcpu),
a4c4af7c HC	638	any_online_cpu(cpu_online_map));
1da177e4	639	case CPU_DEAD:
1c6b4aa9 ST	640	case CPU_DEAD_FROZEN: {
	641	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
	642
1da177e4 LT	643	p = per_cpu(ksoftirqd, hotcpu);
1da177e4 LT	644	per_cpu(ksoftirqd, hotcpu) = NULL;
1c6b4aa9	645	sched_setscheduler(p, SCHED_FIFO, &param);
1da177e4 LT	646	kthread_stop(p);
	647	takeover_tasklets(hotcpu);
	648	break;
1c6b4aa9	649	}
1da177e4 LT	650	#endif /* CONFIG_HOTPLUG_CPU */
	651	}
	652	return NOTIFY_OK;
	653	}
	654
8c78f307	655	static struct notifier_block __cpuinitdata cpu_nfb = {
1da177e4 LT	656	.notifier_call = cpu_callback
	657	};
	658
	659	__init int spawn_ksoftirqd(void)
	660	{
	661	void cpu = (void )(long)smp_processor_id();
07dccf33 AM	662	int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
	663
	664	BUG_ON(err == NOTIFY_BAD);
1da177e4 LT	665	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
	666	register_cpu_notifier(&cpu_nfb);
	667	return 0;
	668	}
78eef01b AM	669
	670	#ifdef CONFIG_SMP
	671	/*
	672	* Call a function on all processors
	673	*/
	674	int on_each_cpu(void (func) (void info), void *info, int retry, int wait)
	675	{
	676	int ret = 0;
	677
	678	preempt_disable();
	679	ret = smp_call_function(func, info, retry, wait);
	680	local_irq_disable();
	681	func(info);
	682	local_irq_enable();
	683	preempt_enable();
	684	return ret;
	685	}
	686	EXPORT_SYMBOL(on_each_cpu);
	687	#endif