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)
142  * local_bh_blocked() - Check for idle whether BH processing is blocked
166 	if (!current->softirq_disable_cnt) {  in __local_bh_disable_ip()
185 	current->softirq_disable_cnt = newcnt;  in __local_bh_disable_ip()
200 	DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=  in __local_bh_enable()
210 	current->softirq_disable_cnt = newcnt;  in __local_bh_enable()
307  * idle load balancing. If soft interrupts get raised which haven't been
324  * This one is for softirq.c-internal use, where hardirqs are disabled
338 	 * is set and before current->softirq_enabled is cleared.  in __local_bh_disable_ip()
352 		current->preempt_disable_ip = get_lock_parent_ip();  in __local_bh_disable_ip()
374  * Special-case - softirqs can safely be enabled by __do_softirq(),
375  * without processing still-pending softirqs:
400 	__preempt_count_sub(cnt - 1);  in __local_bh_enable_ip()
496  * The two things to balance is latency against fairness -
507  * not miss-qualify lock contexts and miss possible deadlocks.
539 	unsigned long old_flags = current->flags;  in handle_softirqs()
551 	current->flags &= ~PF_MEMALLOC;  in handle_softirqs()
571 		h += softirq_bit - 1;  in handle_softirqs()
573 		vec_nr = h - softirq_vec;  in handle_softirqs()
579 		h->action();  in handle_softirqs()
583 			       vec_nr, softirq_to_name[vec_nr], h->action,  in handle_softirqs()
599 		    --max_restart)  in handle_softirqs()
617  * irq_enter_rcu - Enter an interrupt context with RCU watching
631  * irq_enter - Enter an interrupt context including RCU update
690  * irq_exit_rcu() - Exit an interrupt context without updating RCU
702  * irq_exit - Exit an interrupt context, update RCU and lockdep
723 	 * (this also catches softirq-disabled code). We will  in raise_softirq_irqoff()
759 	struct tasklet_struct *head;  member
766 static void __tasklet_schedule_common(struct tasklet_struct *t,  in __tasklet_schedule_common()  argument
770 	struct tasklet_head *head;  in __tasklet_schedule_common()  local
774 	head = this_cpu_ptr(headp);  in __tasklet_schedule_common()
775 	t->next = NULL;  in __tasklet_schedule_common()
776 	*head->tail = t;  in __tasklet_schedule_common()
777 	head->tail = &(t->next);  in __tasklet_schedule_common()
782 void __tasklet_schedule(struct tasklet_struct *t)  in __tasklet_schedule()  argument
784 	__tasklet_schedule_common(t, &tasklet_vec,  in __tasklet_schedule()
789 void __tasklet_hi_schedule(struct tasklet_struct *t)  in __tasklet_hi_schedule()  argument
791 	__tasklet_schedule_common(t, &tasklet_hi_vec,  in __tasklet_hi_schedule()
796 static bool tasklet_clear_sched(struct tasklet_struct *t)  in tasklet_clear_sched()  argument
798 	if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))  in tasklet_clear_sched()
802 		  t->use_callback ? "callback" : "func",  in tasklet_clear_sched()
803 		  t->use_callback ? (void *)t->callback : (void *)t->func);  in tasklet_clear_sched()
814 	list = tl_head->head;  in tasklet_action_common()
815 	tl_head->head = NULL;  in tasklet_action_common()
816 	tl_head->tail = &tl_head->head;  in tasklet_action_common()
820 		struct tasklet_struct *t = list;  in tasklet_action_common()  local
822 		list = list->next;  in tasklet_action_common()
824 		if (tasklet_trylock(t)) {  in tasklet_action_common()
825 			if (!atomic_read(&t->count)) {  in tasklet_action_common()
826 				if (tasklet_clear_sched(t)) {  in tasklet_action_common()
827 					if (t->use_callback) {  in tasklet_action_common()
828 						trace_tasklet_entry(t, t->callback);  in tasklet_action_common()
829 						t->callback(t);  in tasklet_action_common()
830 						trace_tasklet_exit(t, t->callback);  in tasklet_action_common()
832 						trace_tasklet_entry(t, t->func);  in tasklet_action_common()
833 						t->func(t->data);  in tasklet_action_common()
834 						trace_tasklet_exit(t, t->func);  in tasklet_action_common()
837 				tasklet_unlock(t);  in tasklet_action_common()
840 			tasklet_unlock(t);  in tasklet_action_common()
844 		t->next = NULL;  in tasklet_action_common()
845 		*tl_head->tail = t;  in tasklet_action_common()
846 		tl_head->tail = &t->next;  in tasklet_action_common()
864 void tasklet_setup(struct tasklet_struct *t,  in tasklet_setup()  argument
867 	t->next = NULL;  in tasklet_setup()
868 	t->state = 0;  in tasklet_setup()
869 	atomic_set(&t->count, 0);  in tasklet_setup()
870 	t->callback = callback;  in tasklet_setup()
871 	t->use_callback = true;  in tasklet_setup()
872 	t->data = 0;  in tasklet_setup()
876 void tasklet_init(struct tasklet_struct *t,  in tasklet_init()  argument
879 	t->next = NULL;  in tasklet_init()
880 	t->state = 0;  in tasklet_init()
881 	atomic_set(&t->count, 0);  in tasklet_init()
882 	t->func = func;  in tasklet_init()
883 	t->use_callback = false;  in tasklet_init()
884 	t->data = data;  in tasklet_init()
893 void tasklet_unlock_spin_wait(struct tasklet_struct *t)  in tasklet_unlock_spin_wait()  argument
895 	while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {  in tasklet_unlock_spin_wait()
914 void tasklet_kill(struct tasklet_struct *t)  in tasklet_kill()  argument
919 	wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);  in tasklet_kill()
921 	tasklet_unlock_wait(t);  in tasklet_kill()
922 	tasklet_clear_sched(t);  in tasklet_kill()
927 void tasklet_unlock(struct tasklet_struct *t)  in tasklet_unlock()  argument
929 	clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);  in tasklet_unlock()
933 void tasklet_unlock_wait(struct tasklet_struct *t)  in tasklet_unlock_wait()  argument
935 	wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);  in tasklet_unlock_wait()
946 			&per_cpu(tasklet_vec, cpu).head;  in softirq_init()
948 			&per_cpu(tasklet_hi_vec, cpu).head;  in softirq_init()
985 	if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {  in takeover_tasklets()
986 		*__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
988 		per_cpu(tasklet_vec, cpu).head = NULL;  in takeover_tasklets()
989 		per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
993 	if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {  in takeover_tasklets()
994 		*__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()
996 		per_cpu(tasklet_hi_vec, cpu).head = NULL;  in takeover_tasklets()
997 		per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()