/* *	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) * *	Remote softirq infrastructure is by Jens Axboe. */ #include <linux/export.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/ftrace.h>#include <linux/smp.h>#include <linux/tick.h> #define CREATE_TRACE_POINTS#include <trace/events/irq.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_STATirq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;EXPORT_SYMBOL(irq_stat);#endif static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; DEFINE_PER_CPU(struct task_struct *, ksoftirqd); char *softirq_to_name[NR_SOFTIRQS] = {	"HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",	"TASKLET", "SCHED", "HRTIMER", "RCU"}; /* * 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 void wakeup_softirqd(void){	/* Interrupts are disabled: no need to stop preemption */	struct task_struct *tsk = __this_cpu_read(ksoftirqd); 	if (tsk && tsk->state != TASK_RUNNING)		wake_up_process(tsk);} /* * preempt_count and SOFTIRQ_OFFSET usage: * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving *   softirq processing. * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) *   on local_bh_disable or local_bh_enable. * This lets us distinguish between whether we are currently processing * softirq and whether we just have bh disabled. */ /* * This one is for softirq.c-internal use, * where hardirqs are disabled legitimately: */#ifdef CONFIG_TRACE_IRQFLAGSstatic void __local_bh_disable(unsigned long ip, unsigned int cnt){	unsigned long flags; 	WARN_ON_ONCE(in_irq()); 	raw_local_irq_save(flags);	/*	 * The preempt tracer hooks into add_preempt_count and will break	 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET	 * is set and before current->softirq_enabled is cleared.	 * We must manually increment preempt_count here and manually	 * call the trace_preempt_off later.	 */	preempt_count() += cnt;	/*	 * Were softirqs turned off above:	 */	if (softirq_count() == cnt)		trace_softirqs_off(ip);	raw_local_irq_restore(flags); 	if (preempt_count() == cnt)		trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));}#else /* !CONFIG_TRACE_IRQFLAGS */static inline void __local_bh_disable(unsigned long ip, unsigned int cnt){	add_preempt_count(cnt);	barrier();}#endif /* CONFIG_TRACE_IRQFLAGS */ void local_bh_disable(void){	__local_bh_disable((unsigned long)__builtin_return_address(0),				SOFTIRQ_DISABLE_OFFSET);} EXPORT_SYMBOL(local_bh_disable); static void __local_bh_enable(unsigned int cnt){	WARN_ON_ONCE(in_irq());	WARN_ON_ONCE(!irqs_disabled()); 	if (softirq_count() == cnt)		trace_softirqs_on((unsigned long)__builtin_return_address(0));	sub_preempt_count(cnt);} /* * 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){	__local_bh_enable(SOFTIRQ_DISABLE_OFFSET);} EXPORT_SYMBOL(_local_bh_enable); static inline void _local_bh_enable_ip(unsigned long ip){	WARN_ON_ONCE(in_irq() || irqs_disabled());#ifdef CONFIG_TRACE_IRQFLAGS	local_irq_disable();#endif	/*	 * Are softirqs going to be turned on now:	 */	if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)		trace_softirqs_on(ip);	/*	 * Keep preemption disabled until we are done with	 * softirq processing: 	 */	sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1); 	if (unlikely(!in_interrupt() && local_softirq_pending()))		do_softirq(); 	dec_preempt_count();#ifdef CONFIG_TRACE_IRQFLAGS	local_irq_enable();#endif	preempt_check_resched();} void local_bh_enable(void){	_local_bh_enable_ip((unsigned long)__builtin_return_address(0));}EXPORT_SYMBOL(local_bh_enable); void local_bh_enable_ip(unsigned long ip){	_local_bh_enable_ip(ip);}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),				SOFTIRQ_OFFSET);	lockdep_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) {			unsigned int vec_nr = h - softirq_vec;			int prev_count = preempt_count(); 			kstat_incr_softirqs_this_cpu(vec_nr); 			trace_softirq_entry(vec_nr);			h->action(h);			trace_softirq_exit(vec_nr);			if (unlikely(prev_count != preempt_count())) {				printk(KERN_ERR "huh, entered softirq %u %s %p"				       "with preempt_count %08x,"				       " exited with %08x?\n", vec_nr,				       softirq_to_name[vec_nr], h->action,				       prev_count, preempt_count());				preempt_count() = prev_count;			} 			rcu_bh_qs(cpu);		}		h++;		pending >>= 1;	} while (pending); 	local_irq_disable(); 	pending = local_softirq_pending();	if (pending && --max_restart)		goto restart; 	if (pending)		wakeup_softirqd(); 	lockdep_softirq_exit(); 	account_system_vtime(current);	__local_bh_enable(SOFTIRQ_OFFSET);} #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){	int cpu = smp_processor_id(); 	rcu_irq_enter();	if (is_idle_task(current) && !in_interrupt()) {		/*		 * Prevent raise_softirq from needlessly waking up ksoftirqd		 * here, as softirq will be serviced on return from interrupt.		 */		local_bh_disable();		tick_check_idle(cpu);		_local_bh_enable();	} 	__irq_enter();} static inline void invoke_softirq(void){	if (!force_irqthreads) {#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED		__do_softirq();#else		do_softirq();#endif	} else {		__local_bh_disable((unsigned long)__builtin_return_address(0),				SOFTIRQ_OFFSET);		wakeup_softirqd();		__local_bh_enable(SOFTIRQ_OFFSET);	}} /* * 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 (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())		tick_nohz_irq_exit();#endif	rcu_irq_exit();	sched_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 __raise_softirq_irqoff(unsigned int nr){	trace_softirq_raise(nr);	or_softirq_pending(1UL << nr);} 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;	*__this_cpu_read(tasklet_vec.tail) = t;	__this_cpu_write(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;	*__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);} EXPORT_SYMBOL(__tasklet_hi_schedule); void __tasklet_hi_schedule_first(struct tasklet_struct *t){	BUG_ON(!irqs_disabled()); 	t->next = __this_cpu_read(tasklet_hi_vec.head);	__this_cpu_write(tasklet_hi_vec.head, t);	__raise_softirq_irqoff(HI_SOFTIRQ);} EXPORT_SYMBOL(__tasklet_hi_schedule_first); static void tasklet_action(struct softirq_action *a){	struct tasklet_struct *list; 	local_irq_disable();	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) {		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;		*__this_cpu_read(tasklet_vec.tail) = t;		__this_cpu_write(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 = __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) {		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);		} 

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