1 // SPDX-License-Identifier: GPL-2.0-only
7  *	Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
38    - No shared variables, all the data are CPU local.
39    - If a softirq needs serialization, let it serialize itself
41    - Even if softirq is serialized, only local cpu is marked for
47    - NET RX softirq. It is multithreaded and does not require
49    - NET TX softirq. It kicks software netdevice queues, hence
52    - Tasklets: serialized wrt itself.
71  * but we also don't want to introduce a worst case 1/HZ latency
97  * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
100  * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
130  * local_bh_blocked() - Check for idle whether BH processing is blocked
152 	if (!current->softirq_disable_cnt) {  in __local_bh_disable_ip()
171 	current->softirq_disable_cnt = newcnt;  in __local_bh_disable_ip()
186 	DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=  in __local_bh_enable()
196 	current->softirq_disable_cnt = newcnt;  in __local_bh_enable()
287  * get raised which haven't been raised before the flush, warn so it can be
299  * This one is for softirq.c-internal use, where hardirqs are disabled
313 	 * is set and before current->softirq_enabled is cleared.  in __local_bh_disable_ip()
327 		current->preempt_disable_ip = get_lock_parent_ip();  in __local_bh_disable_ip()
349  * Special-case - softirqs can safely be enabled by __do_softirq(),
350  * without processing still-pending softirqs:
375 	__preempt_count_sub(cnt - 1);  in __local_bh_enable_ip()
471  * The two things to balance is latency against fairness -
482  * not miss-qualify lock contexts and miss possible deadlocks.
514 	unsigned long old_flags = current->flags;  in handle_softirqs()
526 	current->flags &= ~PF_MEMALLOC;  in handle_softirqs()
546 		h += softirq_bit - 1;  in handle_softirqs()
548 		vec_nr = h - softirq_vec;  in handle_softirqs()
554 		h->action();  in handle_softirqs()
558 			       vec_nr, softirq_to_name[vec_nr], h->action,  in handle_softirqs()
574 		    --max_restart)  in handle_softirqs()
592  * irq_enter_rcu - Enter an interrupt context with RCU watching
606  * irq_enter - Enter an interrupt context including RCU update
643  * irq_exit_rcu() - Exit an interrupt context without updating RCU
655  * irq_exit - Exit an interrupt context, update RCU and lockdep
676 	 * (this also catches softirq-disabled code). We will  in raise_softirq_irqoff()
712 	struct tasklet_struct *head;  member
719 static void __tasklet_schedule_common(struct tasklet_struct *t,  in __tasklet_schedule_common()  argument
723 	struct tasklet_head *head;  in __tasklet_schedule_common()  local
727 	head = this_cpu_ptr(headp);  in __tasklet_schedule_common()
728 	t->next = NULL;  in __tasklet_schedule_common()
729 	*head->tail = t;  in __tasklet_schedule_common()
730 	head->tail = &(t->next);  in __tasklet_schedule_common()
735 void __tasklet_schedule(struct tasklet_struct *t)  in __tasklet_schedule()  argument
737 	__tasklet_schedule_common(t, &tasklet_vec,  in __tasklet_schedule()
742 void __tasklet_hi_schedule(struct tasklet_struct *t)  in __tasklet_hi_schedule()  argument
744 	__tasklet_schedule_common(t, &tasklet_hi_vec,  in __tasklet_hi_schedule()
749 static bool tasklet_clear_sched(struct tasklet_struct *t)  in tasklet_clear_sched()  argument
751 	if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {  in tasklet_clear_sched()
752 		wake_up_var(&t->state);  in tasklet_clear_sched()
757 		  t->use_callback ? "callback" : "func",  in tasklet_clear_sched()
758 		  t->use_callback ? (void *)t->callback : (void *)t->func);  in tasklet_clear_sched()
769 	list = tl_head->head;  in tasklet_action_common()
770 	tl_head->head = NULL;  in tasklet_action_common()
771 	tl_head->tail = &tl_head->head;  in tasklet_action_common()
775 		struct tasklet_struct *t = list;  in tasklet_action_common()  local
777 		list = list->next;  in tasklet_action_common()
779 		if (tasklet_trylock(t)) {  in tasklet_action_common()
780 			if (!atomic_read(&t->count)) {  in tasklet_action_common()
781 				if (tasklet_clear_sched(t)) {  in tasklet_action_common()
782 					if (t->use_callback) {  in tasklet_action_common()
783 						trace_tasklet_entry(t, t->callback);  in tasklet_action_common()
784 						t->callback(t);  in tasklet_action_common()
785 						trace_tasklet_exit(t, t->callback);  in tasklet_action_common()
787 						trace_tasklet_entry(t, t->func);  in tasklet_action_common()
788 						t->func(t->data);  in tasklet_action_common()
789 						trace_tasklet_exit(t, t->func);  in tasklet_action_common()
792 				tasklet_unlock(t);  in tasklet_action_common()
795 			tasklet_unlock(t);  in tasklet_action_common()
799 		t->next = NULL;  in tasklet_action_common()
800 		*tl_head->tail = t;  in tasklet_action_common()
801 		tl_head->tail = &t->next;  in tasklet_action_common()
819 void tasklet_setup(struct tasklet_struct *t,  in tasklet_setup()  argument
822 	t->next = NULL;  in tasklet_setup()
823 	t->state = 0;  in tasklet_setup()
824 	atomic_set(&t->count, 0);  in tasklet_setup()
825 	t->callback = callback;  in tasklet_setup()
826 	t->use_callback = true;  in tasklet_setup()
827 	t->data = 0;  in tasklet_setup()
831 void tasklet_init(struct tasklet_struct *t,  in tasklet_init()  argument
834 	t->next = NULL;  in tasklet_init()
835 	t->state = 0;  in tasklet_init()
836 	atomic_set(&t->count, 0);  in tasklet_init()
837 	t->func = func;  in tasklet_init()
838 	t->use_callback = false;  in tasklet_init()
839 	t->data = data;  in tasklet_init()
848 void tasklet_unlock_spin_wait(struct tasklet_struct *t)  in tasklet_unlock_spin_wait()  argument
850 	while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {  in tasklet_unlock_spin_wait()
869 void tasklet_kill(struct tasklet_struct *t)  in tasklet_kill()  argument
874 	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))  in tasklet_kill()
875 		wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));  in tasklet_kill()
877 	tasklet_unlock_wait(t);  in tasklet_kill()
878 	tasklet_clear_sched(t);  in tasklet_kill()
883 void tasklet_unlock(struct tasklet_struct *t)  in tasklet_unlock()  argument
886 	clear_bit(TASKLET_STATE_RUN, &t->state);  in tasklet_unlock()
888 	wake_up_var(&t->state);  in tasklet_unlock()
892 void tasklet_unlock_wait(struct tasklet_struct *t)  in tasklet_unlock_wait()  argument
894 	wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));  in tasklet_unlock_wait()
905 			&per_cpu(tasklet_vec, cpu).head;  in softirq_init()
907 			&per_cpu(tasklet_hi_vec, cpu).head;  in softirq_init()
944 	if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {  in takeover_tasklets()
945 		*__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
947 		per_cpu(tasklet_vec, cpu).head = NULL;  in takeover_tasklets()
948 		per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
952 	if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {  in takeover_tasklets()
953 		*__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()
955 		per_cpu(tasklet_hi_vec, cpu).head = NULL;  in takeover_tasklets()
956 		per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()