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)
37    - No shared variables, all the data are CPU local.
38    - If a softirq needs serialization, let it serialize itself
40    - Even if softirq is serialized, only local cpu is marked for
46    - NET RX softirq. It is multithreaded and does not require
48    - NET TX softirq. It kicks software netdevice queues, hence
51    - Tasklets: serialized wrt itself.
70  * but we also don't want to introduce a worst case 1/HZ latency
96  * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
99  * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
129  * local_bh_blocked() - Check for idle whether BH processing is blocked
151 	if (!current->softirq_disable_cnt) {  in __local_bh_disable_ip()
170 	current->softirq_disable_cnt = newcnt;  in __local_bh_disable_ip()
185 	DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=  in __local_bh_enable()
195 	current->softirq_disable_cnt = newcnt;  in __local_bh_enable()
286  * get raised which haven't been raised before the flush, warn so it can be
298  * This one is for softirq.c-internal use, where hardirqs are disabled
312 	 * is set and before current->softirq_enabled is cleared.  in __local_bh_disable_ip()
326 		current->preempt_disable_ip = get_lock_parent_ip();  in __local_bh_disable_ip()
348  * Special-case - softirqs can safely be enabled by __do_softirq(),
349  * without processing still-pending softirqs:
374 	__preempt_count_sub(cnt - 1);  in __local_bh_enable_ip()
470  * The two things to balance is latency against fairness -
481  * not miss-qualify lock contexts and miss possible deadlocks.
513 	unsigned long old_flags = current->flags;  in __do_softirq()
525 	current->flags &= ~PF_MEMALLOC;  in __do_softirq()
545 		h += softirq_bit - 1;  in __do_softirq()
547 		vec_nr = h - softirq_vec;  in __do_softirq()
553 		h->action(h);  in __do_softirq()
557 			       vec_nr, softirq_to_name[vec_nr], h->action,  in __do_softirq()
574 		    --max_restart)  in __do_softirq()
587  * irq_enter_rcu - Enter an interrupt context with RCU watching
601  * irq_enter - Enter an interrupt context including RCU update
638  * irq_exit_rcu() - Exit an interrupt context without updating RCU
650  * irq_exit - Exit an interrupt context, update RCU and lockdep
671 	 * (this also catches softirq-disabled code). We will  in raise_softirq_irqoff()
707 	struct tasklet_struct *head;  member
714 static void __tasklet_schedule_common(struct tasklet_struct *t,  in __tasklet_schedule_common()  argument
718 	struct tasklet_head *head;  in __tasklet_schedule_common()  local
722 	head = this_cpu_ptr(headp);  in __tasklet_schedule_common()
723 	t->next = NULL;  in __tasklet_schedule_common()
724 	*head->tail = t;  in __tasklet_schedule_common()
725 	head->tail = &(t->next);  in __tasklet_schedule_common()
730 void __tasklet_schedule(struct tasklet_struct *t)  in __tasklet_schedule()  argument
732 	__tasklet_schedule_common(t, &tasklet_vec,  in __tasklet_schedule()
737 void __tasklet_hi_schedule(struct tasklet_struct *t)  in __tasklet_hi_schedule()  argument
739 	__tasklet_schedule_common(t, &tasklet_hi_vec,  in __tasklet_hi_schedule()
744 static bool tasklet_clear_sched(struct tasklet_struct *t)  in tasklet_clear_sched()  argument
746 	if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {  in tasklet_clear_sched()
747 		wake_up_var(&t->state);  in tasklet_clear_sched()
752 		  t->use_callback ? "callback" : "func",  in tasklet_clear_sched()
753 		  t->use_callback ? (void *)t->callback : (void *)t->func);  in tasklet_clear_sched()
765 	list = tl_head->head;  in tasklet_action_common()
766 	tl_head->head = NULL;  in tasklet_action_common()
767 	tl_head->tail = &tl_head->head;  in tasklet_action_common()
771 		struct tasklet_struct *t = list;  in tasklet_action_common()  local
773 		list = list->next;  in tasklet_action_common()
775 		if (tasklet_trylock(t)) {  in tasklet_action_common()
776 			if (!atomic_read(&t->count)) {  in tasklet_action_common()
777 				if (tasklet_clear_sched(t)) {  in tasklet_action_common()
778 					if (t->use_callback) {  in tasklet_action_common()
779 						trace_tasklet_entry(t, t->callback);  in tasklet_action_common()
780 						t->callback(t);  in tasklet_action_common()
781 						trace_tasklet_exit(t, t->callback);  in tasklet_action_common()
783 						trace_tasklet_entry(t, t->func);  in tasklet_action_common()
784 						t->func(t->data);  in tasklet_action_common()
785 						trace_tasklet_exit(t, t->func);  in tasklet_action_common()
788 				tasklet_unlock(t);  in tasklet_action_common()
791 			tasklet_unlock(t);  in tasklet_action_common()
795 		t->next = NULL;  in tasklet_action_common()
796 		*tl_head->tail = t;  in tasklet_action_common()
797 		tl_head->tail = &t->next;  in tasklet_action_common()
813 void tasklet_setup(struct tasklet_struct *t,  in tasklet_setup()  argument
816 	t->next = NULL;  in tasklet_setup()
817 	t->state = 0;  in tasklet_setup()
818 	atomic_set(&t->count, 0);  in tasklet_setup()
819 	t->callback = callback;  in tasklet_setup()
820 	t->use_callback = true;  in tasklet_setup()
821 	t->data = 0;  in tasklet_setup()
825 void tasklet_init(struct tasklet_struct *t,  in tasklet_init()  argument
828 	t->next = NULL;  in tasklet_init()
829 	t->state = 0;  in tasklet_init()
830 	atomic_set(&t->count, 0);  in tasklet_init()
831 	t->func = func;  in tasklet_init()
832 	t->use_callback = false;  in tasklet_init()
833 	t->data = data;  in tasklet_init()
842 void tasklet_unlock_spin_wait(struct tasklet_struct *t)  in tasklet_unlock_spin_wait()  argument
844 	while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {  in tasklet_unlock_spin_wait()
863 void tasklet_kill(struct tasklet_struct *t)  in tasklet_kill()  argument
868 	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))  in tasklet_kill()
869 		wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));  in tasklet_kill()
871 	tasklet_unlock_wait(t);  in tasklet_kill()
872 	tasklet_clear_sched(t);  in tasklet_kill()
877 void tasklet_unlock(struct tasklet_struct *t)  in tasklet_unlock()  argument
880 	clear_bit(TASKLET_STATE_RUN, &t->state);  in tasklet_unlock()
882 	wake_up_var(&t->state);  in tasklet_unlock()
886 void tasklet_unlock_wait(struct tasklet_struct *t)  in tasklet_unlock_wait()  argument
888 	wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));  in tasklet_unlock_wait()
899 			&per_cpu(tasklet_vec, cpu).head;  in softirq_init()
901 			&per_cpu(tasklet_hi_vec, cpu).head;  in softirq_init()
936 	if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {  in takeover_tasklets()
937 		*__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
939 		per_cpu(tasklet_vec, cpu).head = NULL;  in takeover_tasklets()
940 		per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;  in takeover_tasklets()
944 	if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {  in takeover_tasklets()
945 		*__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()
947 		per_cpu(tasklet_hi_vec, cpu).head = NULL;  in takeover_tasklets()
948 		per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;  in takeover_tasklets()