[linux-2.6-block.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();
#endif
	preempt_enable_no_resched();
}

/*
 * This function must run with irqs disabled!
 */
inline fastcall 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 fastcall 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*), void *data)
{
	softirq_vec[nr].data = data;
	softirq_vec[nr].action = action;
}

/* Tasklets */
struct tasklet_head
{
	struct tasklet_struct *list;
};

/* Some compilers disobey section attribute on statics when not
   initialized -- RR */
static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };
static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };

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

	local_irq_save(flags);
	t->next = __get_cpu_var(tasklet_vec).list;
	__get_cpu_var(tasklet_vec).list = t;
	raise_softirq_irqoff(TASKLET_SOFTIRQ);
	local_irq_restore(flags);
}

EXPORT_SYMBOL(__tasklet_schedule);

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

	local_irq_save(flags);
	t->next = __get_cpu_var(tasklet_hi_vec).list;
	__get_cpu_var(tasklet_hi_vec).list = t;
	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).list;
	__get_cpu_var(tasklet_vec).list = NULL;
	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 = __get_cpu_var(tasklet_vec).list;
		__get_cpu_var(tasklet_vec).list = t;
		__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).list;
	__get_cpu_var(tasklet_hi_vec).list = NULL;
	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 = __get_cpu_var(tasklet_hi_vec).list;
		__get_cpu_var(tasklet_hi_vec).list = t;
		__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)
{
	open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
	open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
}

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).list; *i; i = &(*i)->next) {
		if (*i == t) {
			*i = t->next;
			return;
		}
	}
	BUG();
}

static void takeover_tasklets(unsigned int cpu)
{
	struct tasklet_struct **i;

	/* CPU is dead, so no lock needed. */
	local_irq_disable();

	/* Find end, append list for that CPU. */
	for (i = &__get_cpu_var(tasklet_vec).list; *i; i = &(*i)->next);
	*i = per_cpu(tasklet_vec, cpu).list;
	per_cpu(tasklet_vec, cpu).list = NULL;
	raise_softirq_irqoff(TASKLET_SOFTIRQ);

	for (i = &__get_cpu_var(tasklet_hi_vec).list; *i; i = &(*i)->next);
	*i = per_cpu(tasklet_hi_vec, cpu).list;
	per_cpu(tasklet_hi_vec, cpu).list = NULL;
	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();
	316	#endif
1da177e4 LT	317	preempt_enable_no_resched();
	318	}
	319
	320	/*
	321	* This function must run with irqs disabled!
	322	*/
	323	inline fastcall void raise_softirq_irqoff(unsigned int nr)
	324	{
	325	__raise_softirq_irqoff(nr);
	326
	327	/*
	328	* If we're in an interrupt or softirq, we're done
	329	* (this also catches softirq-disabled code). We will
	330	* actually run the softirq once we return from
	331	* the irq or softirq.
	332	*
	333	* Otherwise we wake up ksoftirqd to make sure we
	334	* schedule the softirq soon.
	335	*/
	336	if (!in_interrupt())
	337	wakeup_softirqd();
	338	}
	339
1da177e4 LT	340	void fastcall raise_softirq(unsigned int nr)
	341	{
	342	unsigned long flags;
	343
	344	local_irq_save(flags);
	345	raise_softirq_irqoff(nr);
	346	local_irq_restore(flags);
	347	}
	348
	349	void open_softirq(int nr, void (action)(struct softirq_action), void *data)
	350	{
	351	softirq_vec[nr].data = data;
	352	softirq_vec[nr].action = action;
	353	}
	354
1da177e4 LT	355	/* Tasklets */
	356	struct tasklet_head
	357	{
	358	struct tasklet_struct *list;
	359	};
	360
	361	/* Some compilers disobey section attribute on statics when not
	362	initialized -- RR */
	363	static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };
	364	static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };
	365
	366	void fastcall __tasklet_schedule(struct tasklet_struct *t)
	367	{
	368	unsigned long flags;
	369
	370	local_irq_save(flags);
	371	t->next = __get_cpu_var(tasklet_vec).list;
	372	__get_cpu_var(tasklet_vec).list = t;
	373	raise_softirq_irqoff(TASKLET_SOFTIRQ);
	374	local_irq_restore(flags);
	375	}
	376
	377	EXPORT_SYMBOL(__tasklet_schedule);
	378
	379	void fastcall __tasklet_hi_schedule(struct tasklet_struct *t)
	380	{
	381	unsigned long flags;
	382
	383	local_irq_save(flags);
	384	t->next = __get_cpu_var(tasklet_hi_vec).list;
	385	__get_cpu_var(tasklet_hi_vec).list = t;
	386	raise_softirq_irqoff(HI_SOFTIRQ);
	387	local_irq_restore(flags);
	388	}
	389
	390	EXPORT_SYMBOL(__tasklet_hi_schedule);
	391
	392	static void tasklet_action(struct softirq_action *a)
	393	{
	394	struct tasklet_struct *list;
	395
	396	local_irq_disable();
	397	list = __get_cpu_var(tasklet_vec).list;
	398	__get_cpu_var(tasklet_vec).list = NULL;
	399	local_irq_enable();
	400
	401	while (list) {
	402	struct tasklet_struct *t = list;
	403
	404	list = list->next;
	405
	406	if (tasklet_trylock(t)) {
	407	if (!atomic_read(&t->count)) {
	408	if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
	409	BUG();
	410	t->func(t->data);
	411	tasklet_unlock(t);
	412	continue;
	413	}
	414	tasklet_unlock(t);
	415	}
	416
	417	local_irq_disable();
	418	t->next = __get_cpu_var(tasklet_vec).list;
419	__get_cpu_var(tasklet_vec).list = t;
420	__raise_softirq_irqoff(TASKLET_SOFTIRQ);
421	local_irq_enable();
422	}
423	}
424
425	static void tasklet_hi_action(struct softirq_action *a)
426	{
427	struct tasklet_struct *list;
428
429	local_irq_disable();
430	list = __get_cpu_var(tasklet_hi_vec).list;
431	__get_cpu_var(tasklet_hi_vec).list = NULL;
432	local_irq_enable();
433
434	while (list) {
435	struct tasklet_struct *t = list;
436
437	list = list->next;
438
439	if (tasklet_trylock(t)) {
440	if (!atomic_read(&t->count)) {
441	if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
442	BUG();
443	t->func(t->data);
444	tasklet_unlock(t);
445	continue;
446	}
447	tasklet_unlock(t);
448	}
449
450	local_irq_disable();
451	t->next = __get_cpu_var(tasklet_hi_vec).list;
452	__get_cpu_var(tasklet_hi_vec).list = t;
453	__raise_softirq_irqoff(HI_SOFTIRQ);
454	local_irq_enable();
455	}
456	}
457
458
459	void tasklet_init(struct tasklet_struct *t,
460	void (*func)(unsigned long), unsigned long data)
461	{
462	t->next = NULL;
463	t->state = 0;
464	atomic_set(&t->count, 0);
465	t->func = func;
466	t->data = data;
467	}
468
469	EXPORT_SYMBOL(tasklet_init);
470
471	void tasklet_kill(struct tasklet_struct *t)
472	{
473	if (in_interrupt())
474	printk("Attempt to kill tasklet from interrupt\n");
475
476	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
477	do
478	yield();
479	while (test_bit(TASKLET_STATE_SCHED, &t->state));
480	}
481	tasklet_unlock_wait(t);
482	clear_bit(TASKLET_STATE_SCHED, &t->state);
483	}
484
485	EXPORT_SYMBOL(tasklet_kill);
486
487	void __init softirq_init(void)
488	{
489	open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
490	open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
491	}
492
493	static int ksoftirqd(void * __bind_cpu)
494	{
1da177e4 LT	495	set_current_state(TASK_INTERRUPTIBLE);
	496
	497	while (!kthread_should_stop()) {
	498	preempt_disable();
	499	if (!local_softirq_pending()) {
	500	preempt_enable_no_resched();
	501	schedule();
	502	preempt_disable();
	503	}
	504
	505	__set_current_state(TASK_RUNNING);
	506
	507	while (local_softirq_pending()) {
	508	/* Preempt disable stops cpu going offline.
	509	If already offline, we'll be on wrong CPU:
	510	don't process */
	511	if (cpu_is_offline((long)__bind_cpu))
	512	goto wait_to_die;
	513	do_softirq();
	514	preempt_enable_no_resched();
	515	cond_resched();
	516	preempt_disable();
	517	}
	518	preempt_enable();
	519	set_current_state(TASK_INTERRUPTIBLE);
	520	}
	521	__set_current_state(TASK_RUNNING);
	522	return 0;
	523
	524	wait_to_die:
	525	preempt_enable();
	526	/* Wait for kthread_stop */
	527	set_current_state(TASK_INTERRUPTIBLE);
	528	while (!kthread_should_stop()) {
	529	schedule();
	530	set_current_state(TASK_INTERRUPTIBLE);
	531	}
	532	__set_current_state(TASK_RUNNING);
	533	return 0;
	534	}
	535
	536	#ifdef CONFIG_HOTPLUG_CPU
	537	/*
	538	* tasklet_kill_immediate is called to remove a tasklet which can already be
	539	* scheduled for execution on @cpu.
	540	*
	541	* Unlike tasklet_kill, this function removes the tasklet
	542	* _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
	543	*
	544	* When this function is called, @cpu must be in the CPU_DEAD state.
	545	*/
	546	void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
	547	{
	548	struct tasklet_struct **i;
	549
	550	BUG_ON(cpu_online(cpu));
	551	BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
	552
	553	if (!test_bit(TASKLET_STATE_SCHED, &t->state))
	554	return;
	555
	556	/* CPU is dead, so no lock needed. */
	557	for (i = &per_cpu(tasklet_vec, cpu).list; i; i = &(i)->next) {
	558	if (*i == t) {
559	*i = t->next;
560	return;
561	}
562	}
563	BUG();
564	}
565
566	static void takeover_tasklets(unsigned int cpu)
567	{
568	struct tasklet_struct **i;
569
570	/* CPU is dead, so no lock needed. */
571	local_irq_disable();
572
573	/* Find end, append list for that CPU. */
574	for (i = &__get_cpu_var(tasklet_vec).list; i; i = &(i)->next);
575	*i = per_cpu(tasklet_vec, cpu).list;
576	per_cpu(tasklet_vec, cpu).list = NULL;
577	raise_softirq_irqoff(TASKLET_SOFTIRQ);
578
579	for (i = &__get_cpu_var(tasklet_hi_vec).list; i; i = &(i)->next);
580	*i = per_cpu(tasklet_hi_vec, cpu).list;
581	per_cpu(tasklet_hi_vec, cpu).list = NULL;
582	raise_softirq_irqoff(HI_SOFTIRQ);
583
584	local_irq_enable();
585	}
586	#endif /* CONFIG_HOTPLUG_CPU */
587
8c78f307	588	static int __cpuinit cpu_callback(struct notifier_block *nfb,
1da177e4 LT	589	unsigned long action,
	590	void *hcpu)
	591	{
	592	int hotcpu = (unsigned long)hcpu;
	593	struct task_struct *p;
	594
	595	switch (action) {
	596	case CPU_UP_PREPARE:
8bb78442	597	case CPU_UP_PREPARE_FROZEN:
1da177e4 LT	598	p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);
	599	if (IS_ERR(p)) {
	600	printk("ksoftirqd for %i failed\n", hotcpu);
	601	return NOTIFY_BAD;
	602	}
	603	kthread_bind(p, hotcpu);
	604	per_cpu(ksoftirqd, hotcpu) = p;
	605	break;
	606	case CPU_ONLINE:
8bb78442	607	case CPU_ONLINE_FROZEN:
1da177e4 LT	608	wake_up_process(per_cpu(ksoftirqd, hotcpu));
	609	break;
	610	#ifdef CONFIG_HOTPLUG_CPU
	611	case CPU_UP_CANCELED:
8bb78442	612	case CPU_UP_CANCELED_FROZEN:
fc75cdfa HC	613	if (!per_cpu(ksoftirqd, hotcpu))
fc75cdfa HC	614	break;
1da177e4	615	/* Unbind so it can run. Fall thru. */
a4c4af7c HC	616	kthread_bind(per_cpu(ksoftirqd, hotcpu),
a4c4af7c HC	617	any_online_cpu(cpu_online_map));
1da177e4	618	case CPU_DEAD:
1c6b4aa9 ST	619	case CPU_DEAD_FROZEN: {
	620	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
	621
1da177e4 LT	622	p = per_cpu(ksoftirqd, hotcpu);
1da177e4 LT	623	per_cpu(ksoftirqd, hotcpu) = NULL;
1c6b4aa9	624	sched_setscheduler(p, SCHED_FIFO, &param);
1da177e4 LT	625	kthread_stop(p);
	626	takeover_tasklets(hotcpu);
	627	break;
1c6b4aa9	628	}
1da177e4 LT	629	#endif /* CONFIG_HOTPLUG_CPU */
	630	}
	631	return NOTIFY_OK;
	632	}
	633
8c78f307	634	static struct notifier_block __cpuinitdata cpu_nfb = {
1da177e4 LT	635	.notifier_call = cpu_callback
	636	};
	637
	638	__init int spawn_ksoftirqd(void)
	639	{
	640	void cpu = (void )(long)smp_processor_id();
07dccf33 AM	641	int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
	642
	643	BUG_ON(err == NOTIFY_BAD);
1da177e4 LT	644	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
	645	register_cpu_notifier(&cpu_nfb);
	646	return 0;
	647	}
78eef01b AM	648
	649	#ifdef CONFIG_SMP
	650	/*
	651	* Call a function on all processors
	652	*/
	653	int on_each_cpu(void (func) (void info), void *info, int retry, int wait)
	654	{
	655	int ret = 0;
	656
	657	preempt_disable();
	658	ret = smp_call_function(func, info, retry, wait);
	659	local_irq_disable();
	660	func(info);
	661	local_irq_enable();
	662	preempt_enable();
	663	return ret;
	664	}
	665	EXPORT_SYMBOL(on_each_cpu);
	666	#endif