genirq: Reserve the irq when calling irq_set_chip()
[linux-2.6.git] / kernel / irq / handle.c
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  */
30 void 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  */
40 irqreturn_t no_action(int cpl, void *dev_id)
41 {
42         return IRQ_NONE;
43 }
44
45 static void warn_no_thread(unsigned int irq, struct irqaction *action)
46 {
47         if (test_and_set_bit(IRQTF_WARNED, &action->thread_flags))
48                 return;
49
50         printk(KERN_WARNING "IRQ %d device %s returned IRQ_WAKE_THREAD "
51                "but no thread function available.", irq, action->name);
52 }
53
54 static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
55 {
56         /*
57          * Wake up the handler thread for this action. In case the
58          * thread crashed and was killed we just pretend that we
59          * handled the interrupt. The hardirq handler has disabled the
60          * device interrupt, so no irq storm is lurking. If the
61          * RUNTHREAD bit is already set, nothing to do.
62          */
63         if (test_bit(IRQTF_DIED, &action->thread_flags) ||
64             test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
65                 return;
66
67         /*
68          * It's safe to OR the mask lockless here. We have only two
69          * places which write to threads_oneshot: This code and the
70          * irq thread.
71          *
72          * This code is the hard irq context and can never run on two
73          * cpus in parallel. If it ever does we have more serious
74          * problems than this bitmask.
75          *
76          * The irq threads of this irq which clear their "running" bit
77          * in threads_oneshot are serialized via desc->lock against
78          * each other and they are serialized against this code by
79          * IRQS_INPROGRESS.
80          *
81          * Hard irq handler:
82          *
83          *      spin_lock(desc->lock);
84          *      desc->state |= IRQS_INPROGRESS;
85          *      spin_unlock(desc->lock);
86          *      set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
87          *      desc->threads_oneshot |= mask;
88          *      spin_lock(desc->lock);
89          *      desc->state &= ~IRQS_INPROGRESS;
90          *      spin_unlock(desc->lock);
91          *
92          * irq thread:
93          *
94          * again:
95          *      spin_lock(desc->lock);
96          *      if (desc->state & IRQS_INPROGRESS) {
97          *              spin_unlock(desc->lock);
98          *              while(desc->state & IRQS_INPROGRESS)
99          *                      cpu_relax();
100          *              goto again;
101          *      }
102          *      if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
103          *              desc->threads_oneshot &= ~mask;
104          *      spin_unlock(desc->lock);
105          *
106          * So either the thread waits for us to clear IRQS_INPROGRESS
107          * or we are waiting in the flow handler for desc->lock to be
108          * released before we reach this point. The thread also checks
109          * IRQTF_RUNTHREAD under desc->lock. If set it leaves
110          * threads_oneshot untouched and runs the thread another time.
111          */
112         desc->threads_oneshot |= action->thread_mask;
113         wake_up_process(action->thread);
114 }
115
116 irqreturn_t
117 handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
118 {
119         irqreturn_t retval = IRQ_NONE;
120         unsigned int random = 0, irq = desc->irq_data.irq;
121
122         do {
123                 irqreturn_t res;
124
125                 trace_irq_handler_entry(irq, action);
126                 res = action->handler(irq, action->dev_id);
127                 trace_irq_handler_exit(irq, action, res);
128
129                 if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
130                               irq, action->handler))
131                         local_irq_disable();
132
133                 switch (res) {
134                 case IRQ_WAKE_THREAD:
135                         /*
136                          * Set result to handled so the spurious check
137                          * does not trigger.
138                          */
139                         res = IRQ_HANDLED;
140
141                         /*
142                          * Catch drivers which return WAKE_THREAD but
143                          * did not set up a thread function
144                          */
145                         if (unlikely(!action->thread_fn)) {
146                                 warn_no_thread(irq, action);
147                                 break;
148                         }
149
150                         irq_wake_thread(desc, action);
151
152                         /* Fall through to add to randomness */
153                 case IRQ_HANDLED:
154                         random |= action->flags;
155                         break;
156
157                 default:
158                         break;
159                 }
160
161                 retval |= res;
162                 action = action->next;
163         } while (action);
164
165         if (random & IRQF_SAMPLE_RANDOM)
166                 add_interrupt_randomness(irq);
167
168         if (!noirqdebug)
169                 note_interrupt(irq, desc, retval);
170         return retval;
171 }
172
173 irqreturn_t handle_irq_event(struct irq_desc *desc)
174 {
175         struct irqaction *action = desc->action;
176         irqreturn_t ret;
177
178         irq_compat_clr_pending(desc);
179         desc->istate &= ~IRQS_PENDING;
180         irq_compat_set_progress(desc);
181         desc->istate |= IRQS_INPROGRESS;
182         raw_spin_unlock(&desc->lock);
183
184         ret = handle_irq_event_percpu(desc, action);
185
186         raw_spin_lock(&desc->lock);
187         desc->istate &= ~IRQS_INPROGRESS;
188         irq_compat_clr_progress(desc);
189         return ret;
190 }
191
192 /**
193  * handle_IRQ_event - irq action chain handler
194  * @irq:        the interrupt number
195  * @action:     the interrupt action chain for this irq
196  *
197  * Handles the action chain of an irq event
198  */
199 irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
200 {
201         return handle_irq_event_percpu(irq_to_desc(irq), action);
202 }