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 ((action->thread->flags & PF_EXITING) ||
  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
 114         /*
 115          * We increment the threads_active counter in case we wake up
 116          * the irq thread. The irq thread decrements the counter when
 117          * it returns from the handler or in the exit path and wakes
 118          * up waiters which are stuck in synchronize_irq() when the
 119          * active count becomes zero. synchronize_irq() is serialized
 120          * against this code (hard irq handler) via IRQS_INPROGRESS
 121          * like the finalize_oneshot() code. See comment above.
 122          */
 123         atomic_inc(&desc->threads_active);
 124
 125         wake_up_process(action->thread);
 126 }
 127
 128 irqreturn_t
 129 handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
 130 {
 131         irqreturn_t retval = IRQ_NONE;
 132         unsigned int random = 0, irq = desc->irq_data.irq;
 133
 134         do {
 135                 irqreturn_t res;
 136
 137                 trace_irq_handler_entry(irq, action);
 138                 res = action->handler(irq, action->dev_id);
 139                 trace_irq_handler_exit(irq, action, res);
 140
 141                 if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
 142                               irq, action->handler))
 143                         local_irq_disable();
 144
 145                 switch (res) {
 146                 case IRQ_WAKE_THREAD:
 147                         /*
 148                          * Catch drivers which return WAKE_THREAD but
 149                          * did not set up a thread function
 150                          */
 151                         if (unlikely(!action->thread_fn)) {
 152                                 warn_no_thread(irq, action);
 153                                 break;
 154                         }
 155
 156                         irq_wake_thread(desc, action);
 157
 158                         /* Fall through to add to randomness */
 159                 case IRQ_HANDLED:
 160                         random |= action->flags;
 161                         break;
 162
 163                 default:
 164                         break;
 165                 }
 166
 167                 retval |= res;
 168                 action = action->next;
 169         } while (action);
 170
 171         if (random & IRQF_SAMPLE_RANDOM)
 172                 add_interrupt_randomness(irq);
 173
 174         if (!noirqdebug)
 175                 note_interrupt(irq, desc, retval);
 176         return retval;
 177 }
 178
 179 irqreturn_t handle_irq_event(struct irq_desc *desc)
 180 {
 181         struct irqaction *action = desc->action;
 182         irqreturn_t ret;
 183
 184         desc->istate &= ~IRQS_PENDING;
 185         irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 186         raw_spin_unlock(&desc->lock);
 187
 188         ret = handle_irq_event_percpu(desc, action);
 189
 190         raw_spin_lock(&desc->lock);
 191         irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 192         return ret;
 193 }