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  * @desc:      description of the interrupt
  26  *
  27  * Handles spurious and unhandled IRQ's. It also prints a debugmessage.
  28  */
  29 void handle_bad_irq(struct irq_desc *desc)
  30 {
  31         unsigned int irq = irq_desc_get_irq(desc);
  32
  33         print_irq_desc(irq, desc);
  34         kstat_incr_irqs_this_cpu(desc);
  35         ack_bad_irq(irq);
  36 }
  37 EXPORT_SYMBOL_GPL(handle_bad_irq);
  38
  39 /*
  40  * Special, empty irq handler:
  41  */
  42 irqreturn_t no_action(int cpl, void *dev_id)
  43 {
  44         return IRQ_NONE;
  45 }
  46 EXPORT_SYMBOL_GPL(no_action);
  47
  48 static void warn_no_thread(unsigned int irq, struct irqaction *action)
  49 {
  50         if (test_and_set_bit(IRQTF_WARNED, &action->thread_flags))
  51                 return;
  52
  53         printk(KERN_WARNING "IRQ %d device %s returned IRQ_WAKE_THREAD "
  54                "but no thread function available.", irq, action->name);
  55 }
  56
  57 void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
  58 {
  59         /*
  60          * In case the thread crashed and was killed we just pretend that
  61          * we handled the interrupt. The hardirq handler has disabled the
  62          * device interrupt, so no irq storm is lurking.
  63          */
  64         if (action->thread->flags & PF_EXITING)
  65                 return;
  66
  67         /*
  68          * Wake up the handler thread for this action. If the
  69          * RUNTHREAD bit is already set, nothing to do.
  70          */
  71         if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
  72                 return;
  73
  74         /*
  75          * It's safe to OR the mask lockless here. We have only two
  76          * places which write to threads_oneshot: This code and the
  77          * irq thread.
  78          *
  79          * This code is the hard irq context and can never run on two
  80          * cpus in parallel. If it ever does we have more serious
  81          * problems than this bitmask.
  82          *
  83          * The irq threads of this irq which clear their "running" bit
  84          * in threads_oneshot are serialized via desc->lock against
  85          * each other and they are serialized against this code by
  86          * IRQS_INPROGRESS.
  87          *
  88          * Hard irq handler:
  89          *
  90          *      spin_lock(desc->lock);
  91          *      desc->state |= IRQS_INPROGRESS;
  92          *      spin_unlock(desc->lock);
  93          *      set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
  94          *      desc->threads_oneshot |= mask;
  95          *      spin_lock(desc->lock);
  96          *      desc->state &= ~IRQS_INPROGRESS;
  97          *      spin_unlock(desc->lock);
  98          *
  99          * irq thread:
 100          *
 101          * again:
 102          *      spin_lock(desc->lock);
 103          *      if (desc->state & IRQS_INPROGRESS) {
 104          *              spin_unlock(desc->lock);
 105          *              while(desc->state & IRQS_INPROGRESS)
 106          *                      cpu_relax();
 107          *              goto again;
 108          *      }
 109          *      if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
 110          *              desc->threads_oneshot &= ~mask;
 111          *      spin_unlock(desc->lock);
 112          *
 113          * So either the thread waits for us to clear IRQS_INPROGRESS
 114          * or we are waiting in the flow handler for desc->lock to be
 115          * released before we reach this point. The thread also checks
 116          * IRQTF_RUNTHREAD under desc->lock. If set it leaves
 117          * threads_oneshot untouched and runs the thread another time.
 118          */
 119         desc->threads_oneshot |= action->thread_mask;
 120
 121         /*
 122          * We increment the threads_active counter in case we wake up
 123          * the irq thread. The irq thread decrements the counter when
 124          * it returns from the handler or in the exit path and wakes
 125          * up waiters which are stuck in synchronize_irq() when the
 126          * active count becomes zero. synchronize_irq() is serialized
 127          * against this code (hard irq handler) via IRQS_INPROGRESS
 128          * like the finalize_oneshot() code. See comment above.
 129          */
 130         atomic_inc(&desc->threads_active);
 131
 132         wake_up_process(action->thread);
 133 }
 134
 135 irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
 136 {
 137         irqreturn_t retval = IRQ_NONE;
 138         unsigned int flags = 0, irq = desc->irq_data.irq;
 139         struct irqaction *action = desc->action;
 140
 141         /* action might have become NULL since we dropped the lock */
 142         while (action) {
 143                 irqreturn_t res;
 144
 145                 trace_irq_handler_entry(irq, action);
 146                 res = action->handler(irq, action->dev_id);
 147                 trace_irq_handler_exit(irq, action, res);
 148
 149                 if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
 150                               irq, action->handler))
 151                         local_irq_disable();
 152
 153                 switch (res) {
 154                 case IRQ_WAKE_THREAD:
 155                         /*
 156                          * Catch drivers which return WAKE_THREAD but
 157                          * did not set up a thread function
 158                          */
 159                         if (unlikely(!action->thread_fn)) {
 160                                 warn_no_thread(irq, action);
 161                                 break;
 162                         }
 163
 164                         __irq_wake_thread(desc, action);
 165
 166                         /* Fall through to add to randomness */
 167                 case IRQ_HANDLED:
 168                         flags |= action->flags;
 169                         break;
 170
 171                 default:
 172                         break;
 173                 }
 174
 175                 retval |= res;
 176                 action = action->next;
 177         }
 178
 179         add_interrupt_randomness(irq, flags);
 180
 181         if (!noirqdebug)
 182                 note_interrupt(desc, retval);
 183         return retval;
 184 }
 185
 186 irqreturn_t handle_irq_event(struct irq_desc *desc)
 187 {
 188         irqreturn_t ret;
 189
 190         desc->istate &= ~IRQS_PENDING;
 191         irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 192         raw_spin_unlock(&desc->lock);
 193
 194         ret = handle_irq_event_percpu(desc);
 195
 196         raw_spin_lock(&desc->lock);
 197         irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 198         return ret;
 199 }