1/*
2 * linux/kernel/irq/handle.c
3 *
4 * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
5 * Copyright (C) 2005-2006, Thomas Gleixner, Russell King
6 *
7 * This file contains the core interrupt handling code.
8 *
9 * Detailed information is available in Documentation/DocBook/genericirq
10 *
11 */
12
13#include <linux/irq.h>
14#include <linux/random.h>
15#include <linux/sched.h>
16#include <linux/interrupt.h>
17#include <linux/kernel_stat.h>
18
19#include <trace/events/irq.h>
20
21#include "internals.h"
22
23/**
24 * handle_bad_irq - handle spurious and unhandled irqs
25 * @irq:       the interrupt number
26 * @desc:      description of the interrupt
27 *
28 * Handles spurious and unhandled IRQ's. It also prints a debugmessage.
29 */
30void handle_bad_irq(unsigned int irq, struct irq_desc *desc)
31{
32	print_irq_desc(irq, desc);
33	kstat_incr_irqs_this_cpu(irq, desc);
34	ack_bad_irq(irq);
35}
36
37/*
38 * Special, empty irq handler:
39 */
40irqreturn_t no_action(int cpl, void *dev_id)
41{
42	return IRQ_NONE;
43}
44EXPORT_SYMBOL_GPL(no_action);
45
46static void warn_no_thread(unsigned int irq, struct irqaction *action)
47{
48	if (test_and_set_bit(IRQTF_WARNED, &action->thread_flags))
49		return;
50
51	printk(KERN_WARNING "IRQ %d device %s returned IRQ_WAKE_THREAD "
52	       "but no thread function available.", irq, action->name);
53}
54
55void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
56{
57	/*
58	 * In case the thread crashed and was killed we just pretend that
59	 * we handled the interrupt. The hardirq handler has disabled the
60	 * device interrupt, so no irq storm is lurking.
61	 */
62	if (action->thread->flags & PF_EXITING)
63		return;
64
65	/*
66	 * Wake up the handler thread for this action. If the
67	 * RUNTHREAD bit is already set, nothing to do.
68	 */
69	if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
70		return;
71
72	/*
73	 * It's safe to OR the mask lockless here. We have only two
74	 * places which write to threads_oneshot: This code and the
75	 * irq thread.
76	 *
77	 * This code is the hard irq context and can never run on two
78	 * cpus in parallel. If it ever does we have more serious
79	 * problems than this bitmask.
80	 *
81	 * The irq threads of this irq which clear their "running" bit
82	 * in threads_oneshot are serialized via desc->lock against
83	 * each other and they are serialized against this code by
84	 * IRQS_INPROGRESS.
85	 *
86	 * Hard irq handler:
87	 *
88	 *	spin_lock(desc->lock);
89	 *	desc->state |= IRQS_INPROGRESS;
90	 *	spin_unlock(desc->lock);
91	 *	set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
92	 *	desc->threads_oneshot |= mask;
93	 *	spin_lock(desc->lock);
94	 *	desc->state &= ~IRQS_INPROGRESS;
95	 *	spin_unlock(desc->lock);
96	 *
97	 * irq thread:
98	 *
99	 * again:
100	 *	spin_lock(desc->lock);
101	 *	if (desc->state & IRQS_INPROGRESS) {
102	 *		spin_unlock(desc->lock);
103	 *		while(desc->state & IRQS_INPROGRESS)
104	 *			cpu_relax();
105	 *		goto again;
106	 *	}
107	 *	if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
108	 *		desc->threads_oneshot &= ~mask;
109	 *	spin_unlock(desc->lock);
110	 *
111	 * So either the thread waits for us to clear IRQS_INPROGRESS
112	 * or we are waiting in the flow handler for desc->lock to be
113	 * released before we reach this point. The thread also checks
114	 * IRQTF_RUNTHREAD under desc->lock. If set it leaves
115	 * threads_oneshot untouched and runs the thread another time.
116	 */
117	desc->threads_oneshot |= action->thread_mask;
118
119	/*
120	 * We increment the threads_active counter in case we wake up
121	 * the irq thread. The irq thread decrements the counter when
122	 * it returns from the handler or in the exit path and wakes
123	 * up waiters which are stuck in synchronize_irq() when the
124	 * active count becomes zero. synchronize_irq() is serialized
125	 * against this code (hard irq handler) via IRQS_INPROGRESS
126	 * like the finalize_oneshot() code. See comment above.
127	 */
128	atomic_inc(&desc->threads_active);
129
130	wake_up_process(action->thread);
131}
132
133irqreturn_t
134handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
135{
136	irqreturn_t retval = IRQ_NONE;
137	unsigned int flags = 0, irq = desc->irq_data.irq;
138
139	do {
140		irqreturn_t res;
141
142		trace_irq_handler_entry(irq, action);
143		res = action->handler(irq, action->dev_id);
144		trace_irq_handler_exit(irq, action, res);
145
146		if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
147			      irq, action->handler))
148			local_irq_disable();
149
150		switch (res) {
151		case IRQ_WAKE_THREAD:
152			/*
153			 * Catch drivers which return WAKE_THREAD but
154			 * did not set up a thread function
155			 */
156			if (unlikely(!action->thread_fn)) {
157				warn_no_thread(irq, action);
158				break;
159			}
160
161			__irq_wake_thread(desc, action);
162
163			/* Fall through to add to randomness */
164		case IRQ_HANDLED:
165			flags |= action->flags;
166			break;
167
168		default:
169			break;
170		}
171
172		retval |= res;
173		action = action->next;
174	} while (action);
175
176	add_interrupt_randomness(irq, flags);
177
178	if (!noirqdebug)
179		note_interrupt(irq, desc, retval);
180	return retval;
181}
182
183irqreturn_t handle_irq_event(struct irq_desc *desc)
184{
185	struct irqaction *action = desc->action;
186	irqreturn_t ret;
187
188	desc->istate &= ~IRQS_PENDING;
189	irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
190	raw_spin_unlock(&desc->lock);
191
192	ret = handle_irq_event_percpu(desc, action);
193
194	raw_spin_lock(&desc->lock);
195	irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
196	return ret;
197}
198