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()
289  * idle load balancing. If soft interrupts get raised which haven't been
306  * This one is for softirq.c-internal use, where hardirqs are disabled
320 	 * is set and before current->softirq_enabled is cleared.  in __local_bh_disable_ip()
334 		current->preempt_disable_ip = get_lock_parent_ip();  in __local_bh_disable_ip()
356  * Special-case - softirqs can safely be enabled by __do_softirq(),
357  * without processing still-pending softirqs:
382 	__preempt_count_sub(cnt - 1);  in __local_bh_enable_ip()
478  * The two things to balance is latency against fairness -
489  * not miss-qualify lock contexts and miss possible deadlocks.
521 	unsigned long old_flags = current->flags;  in handle_softirqs()
533 	current->flags &= ~PF_MEMALLOC;  in handle_softirqs()
553 		h += softirq_bit - 1;  in handle_softirqs()
555 		vec_nr = h - softirq_vec;  in handle_softirqs()
561 		h->action();  in handle_softirqs()
565 			       vec_nr, softirq_to_name[vec_nr], h->action,  in handle_softirqs()
581 		    --max_restart)  in handle_softirqs()
599  * irq_enter_rcu - Enter an interrupt context with RCU watching
613  * irq_enter - Enter an interrupt context including RCU update
672  * irq_exit_rcu() - Exit an interrupt context without updating RCU
684  * irq_exit - Exit an interrupt context, update RCU and lockdep
705 	 * (this also catches softirq-disabled code). We will  in raise_softirq_irqoff()
741 	struct tasklet_struct *head;  member
748 static void __tasklet_schedule_common(struct tasklet_struct *t,  in __tasklet_schedule_common()  argument
752 	struct tasklet_head *head;  in __tasklet_schedule_common()  local
756 	head = this_cpu_ptr(headp);  in __tasklet_schedule_common()
757 	t->next = NULL;  in __tasklet_schedule_common()
758 	*head->tail = t;  in __tasklet_schedule_common()
759 	head->tail = &(t->next);  in __tasklet_schedule_common()
764 void __tasklet_schedule(struct tasklet_struct *t)  in __tasklet_schedule()  argument
766 	__tasklet_schedule_common(t, &tasklet_vec,  in __tasklet_schedule()
771 void __tasklet_hi_schedule(struct tasklet_struct *t)  in __tasklet_hi_schedule()  argument
773 	__tasklet_schedule_common(t, &tasklet_hi_vec,  in __tasklet_hi_schedule()
778 static bool tasklet_clear_sched(struct tasklet_struct *t)  in tasklet_clear_sched()  argument
780 	if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))  in tasklet_clear_sched()
784 		  t->use_callback ? "callback" : "func",  in tasklet_clear_sched()
785 		  t->use_callback ? (void *)t->callback : (void *)t->func);  in tasklet_clear_sched()
796 	list = tl_head->head;  in tasklet_action_common()
797 	tl_head->head = NULL;  in tasklet_action_common()
798 	tl_head->tail = &tl_head->head;  in tasklet_action_common()
802 		struct tasklet_struct *t = list;  in tasklet_action_common()  local
804 		list = list->next;  in tasklet_action_common()
806 		if (tasklet_trylock(t)) {  in tasklet_action_common()
807 			if (!atomic_read(&t->count)) {  in tasklet_action_common()
808 				if (tasklet_clear_sched(t)) {  in tasklet_action_common()
809 					if (t->use_callback) {  in tasklet_action_common()
810 						trace_tasklet_entry(t, t->callback);  in tasklet_action_common()
811 						t->callback(t);  in tasklet_action_common()
812 						trace_tasklet_exit(t, t->callback);  in tasklet_action_common()
814 						trace_tasklet_entry(t, t->func);  in tasklet_action_common()
815 						t->func(t->data);  in tasklet_action_common()
816 						trace_tasklet_exit(t, t->func);  in tasklet_action_common()
819 				tasklet_unlock(t);  in tasklet_action_common()
822 			tasklet_unlock(t);  in tasklet_action_common()
826 		t->next = NULL;  in tasklet_action_common()
827 		*tl_head->tail = t;  in tasklet_action_common()
828 		tl_head->tail = &t->next;  in tasklet_action_common()
846 void tasklet_setup(struct tasklet_struct *t,  in tasklet_setup()  argument
849 	t->next = NULL;  in tasklet_setup()
850 	t->state = 0;  in tasklet_setup()
851 	atomic_set(&t->count, 0);  in tasklet_setup()
852 	t->callback = callback;  in tasklet_setup()
853 	t->use_callback = true;  in tasklet_setup()
854 	t->data = 0;  in tasklet_setup()
858 void tasklet_init(struct tasklet_struct *t,  in tasklet_init()  argument
861 	t->next = NULL;  in tasklet_init()
862 	t->state = 0;  in tasklet_init()
863 	atomic_set(&t->count, 0);  in tasklet_init()
864 	t->func = func;  in tasklet_init()
865 	t->use_callback = false;  in tasklet_init()
866 	t->data = data;  in tasklet_init()
875 void tasklet_unlock_spin_wait(struct tasklet_struct *t)  in tasklet_unlock_spin_wait()  argument
877 	while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {  in tasklet_unlock_spin_wait()
896 void tasklet_kill(struct tasklet_struct *t)  in tasklet_kill()  argument
901 	wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);  in tasklet_kill()
903 	tasklet_unlock_wait(t);  in tasklet_kill()
904 	tasklet_clear_sched(t);  in tasklet_kill()
909 void tasklet_unlock(struct tasklet_struct *t)  in tasklet_unlock()  argument
911 	clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);  in tasklet_unlock()
915 void tasklet_unlock_wait(struct tasklet_struct *t)  in tasklet_unlock_wait()  argument
917 	wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);  in tasklet_unlock_wait()
928 			&per_cpu(tasklet_vec, cpu).head;  in softirq_init()
930 			&per_cpu(tasklet_hi_vec, cpu).head;  in softirq_init()
967 	if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {  in takeover_tasklets()
968 		*__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
970 		per_cpu(tasklet_vec, cpu).head = NULL;  in takeover_tasklets()
971 		per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
975 	if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {  in takeover_tasklets()
976 		*__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()
978 		per_cpu(tasklet_hi_vec, cpu).head = NULL;  in takeover_tasklets()
979 		per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()