Merge tag 'v3.6-rc2' into drm-intel-next
[firefly-linux-kernel-4.4.55.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          * In case the thread crashed and was killed we just pretend that
58          * we handled the interrupt. The hardirq handler has disabled the
59          * device interrupt, so no irq storm is lurking.
60          */
61         if (action->thread->flags & PF_EXITING)
62                 return;
63
64         /*
65          * Wake up the handler thread for this action. If the
66          * RUNTHREAD bit is already set, nothing to do.
67          */
68         if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
69                 return;
70
71         /*
72          * It's safe to OR the mask lockless here. We have only two
73          * places which write to threads_oneshot: This code and the
74          * irq thread.
75          *
76          * This code is the hard irq context and can never run on two
77          * cpus in parallel. If it ever does we have more serious
78          * problems than this bitmask.
79          *
80          * The irq threads of this irq which clear their "running" bit
81          * in threads_oneshot are serialized via desc->lock against
82          * each other and they are serialized against this code by
83          * IRQS_INPROGRESS.
84          *
85          * Hard irq handler:
86          *
87          *      spin_lock(desc->lock);
88          *      desc->state |= IRQS_INPROGRESS;
89          *      spin_unlock(desc->lock);
90          *      set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
91          *      desc->threads_oneshot |= mask;
92          *      spin_lock(desc->lock);
93          *      desc->state &= ~IRQS_INPROGRESS;
94          *      spin_unlock(desc->lock);
95          *
96          * irq thread:
97          *
98          * again:
99          *      spin_lock(desc->lock);
100          *      if (desc->state & IRQS_INPROGRESS) {
101          *              spin_unlock(desc->lock);
102          *              while(desc->state & IRQS_INPROGRESS)
103          *                      cpu_relax();
104          *              goto again;
105          *      }
106          *      if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
107          *              desc->threads_oneshot &= ~mask;
108          *      spin_unlock(desc->lock);
109          *
110          * So either the thread waits for us to clear IRQS_INPROGRESS
111          * or we are waiting in the flow handler for desc->lock to be
112          * released before we reach this point. The thread also checks
113          * IRQTF_RUNTHREAD under desc->lock. If set it leaves
114          * threads_oneshot untouched and runs the thread another time.
115          */
116         desc->threads_oneshot |= action->thread_mask;
117
118         /*
119          * We increment the threads_active counter in case we wake up
120          * the irq thread. The irq thread decrements the counter when
121          * it returns from the handler or in the exit path and wakes
122          * up waiters which are stuck in synchronize_irq() when the
123          * active count becomes zero. synchronize_irq() is serialized
124          * against this code (hard irq handler) via IRQS_INPROGRESS
125          * like the finalize_oneshot() code. See comment above.
126          */
127         atomic_inc(&desc->threads_active);
128
129         wake_up_process(action->thread);
130 }
131
132 irqreturn_t
133 handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
134 {
135         irqreturn_t retval = IRQ_NONE;
136         unsigned int flags = 0, irq = desc->irq_data.irq;
137
138         do {
139                 irqreturn_t res;
140
141                 trace_irq_handler_entry(irq, action);
142                 res = action->handler(irq, action->dev_id);
143                 trace_irq_handler_exit(irq, action, res);
144
145                 if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
146                               irq, action->handler))
147                         local_irq_disable();
148
149                 switch (res) {
150                 case IRQ_WAKE_THREAD:
151                         /*
152                          * Catch drivers which return WAKE_THREAD but
153                          * did not set up a thread function
154                          */
155                         if (unlikely(!action->thread_fn)) {
156                                 warn_no_thread(irq, action);
157                                 break;
158                         }
159
160                         irq_wake_thread(desc, action);
161
162                         /* Fall through to add to randomness */
163                 case IRQ_HANDLED:
164                         flags |= action->flags;
165                         break;
166
167                 default:
168                         break;
169                 }
170
171                 retval |= res;
172                 action = action->next;
173         } while (action);
174
175         add_interrupt_randomness(irq, flags);
176
177         if (!noirqdebug)
178                 note_interrupt(irq, desc, retval);
179         return retval;
180 }
181
182 irqreturn_t handle_irq_event(struct irq_desc *desc)
183 {
184         struct irqaction *action = desc->action;
185         irqreturn_t ret;
186
187         desc->istate &= ~IRQS_PENDING;
188         irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
189         raw_spin_unlock(&desc->lock);
190
191         ret = handle_irq_event_percpu(desc, action);
192
193         raw_spin_lock(&desc->lock);
194         irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
195         return ret;
196 }