61c679db4687a853c52f7d5b23b5ba5e267b4c17
[linux-2.6.git] / kernel / irq / manage.c
1 /*
2  * linux/kernel/irq/manage.c
3  *
4  * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
5  * Copyright (C) 2005-2006 Thomas Gleixner
6  *
7  * This file contains driver APIs to the irq subsystem.
8  */
9
10 #include <linux/irq.h>
11 #include <linux/kthread.h>
12 #include <linux/module.h>
13 #include <linux/random.h>
14 #include <linux/interrupt.h>
15 #include <linux/slab.h>
16 #include <linux/sched.h>
17
18 #include "internals.h"
19
20 /**
21  *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
22  *      @irq: interrupt number to wait for
23  *
24  *      This function waits for any pending IRQ handlers for this interrupt
25  *      to complete before returning. If you use this function while
26  *      holding a resource the IRQ handler may need you will deadlock.
27  *
28  *      This function may be called - with care - from IRQ context.
29  */
30 void synchronize_irq(unsigned int irq)
31 {
32         struct irq_desc *desc = irq_to_desc(irq);
33         unsigned int status;
34
35         if (!desc)
36                 return;
37
38         do {
39                 unsigned long flags;
40
41                 /*
42                  * Wait until we're out of the critical section.  This might
43                  * give the wrong answer due to the lack of memory barriers.
44                  */
45                 while (desc->status & IRQ_INPROGRESS)
46                         cpu_relax();
47
48                 /* Ok, that indicated we're done: double-check carefully. */
49                 spin_lock_irqsave(&desc->lock, flags);
50                 status = desc->status;
51                 spin_unlock_irqrestore(&desc->lock, flags);
52
53                 /* Oops, that failed? */
54         } while (status & IRQ_INPROGRESS);
55
56         /*
57          * We made sure that no hardirq handler is running. Now verify
58          * that no threaded handlers are active.
59          */
60         wait_event(desc->wait_for_threads, !atomic_read(&desc->threads_active));
61 }
62 EXPORT_SYMBOL(synchronize_irq);
63
64 #ifdef CONFIG_SMP
65 cpumask_var_t irq_default_affinity;
66
67 /**
68  *      irq_can_set_affinity - Check if the affinity of a given irq can be set
69  *      @irq:           Interrupt to check
70  *
71  */
72 int irq_can_set_affinity(unsigned int irq)
73 {
74         struct irq_desc *desc = irq_to_desc(irq);
75
76         if (CHECK_IRQ_PER_CPU(desc->status) || !desc->chip ||
77             !desc->chip->set_affinity)
78                 return 0;
79
80         return 1;
81 }
82
83 /**
84  *      irq_set_thread_affinity - Notify irq threads to adjust affinity
85  *      @desc:          irq descriptor which has affitnity changed
86  *
87  *      We just set IRQTF_AFFINITY and delegate the affinity setting
88  *      to the interrupt thread itself. We can not call
89  *      set_cpus_allowed_ptr() here as we hold desc->lock and this
90  *      code can be called from hard interrupt context.
91  */
92 void irq_set_thread_affinity(struct irq_desc *desc)
93 {
94         struct irqaction *action = desc->action;
95
96         while (action) {
97                 if (action->thread)
98                         set_bit(IRQTF_AFFINITY, &action->thread_flags);
99                 action = action->next;
100         }
101 }
102
103 /**
104  *      irq_set_affinity - Set the irq affinity of a given irq
105  *      @irq:           Interrupt to set affinity
106  *      @cpumask:       cpumask
107  *
108  */
109 int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
110 {
111         struct irq_desc *desc = irq_to_desc(irq);
112         unsigned long flags;
113
114         if (!desc->chip->set_affinity)
115                 return -EINVAL;
116
117         spin_lock_irqsave(&desc->lock, flags);
118
119 #ifdef CONFIG_GENERIC_PENDING_IRQ
120         if (desc->status & IRQ_MOVE_PCNTXT) {
121                 if (!desc->chip->set_affinity(irq, cpumask)) {
122                         cpumask_copy(desc->affinity, cpumask);
123                         irq_set_thread_affinity(desc);
124                 }
125         }
126         else {
127                 desc->status |= IRQ_MOVE_PENDING;
128                 cpumask_copy(desc->pending_mask, cpumask);
129         }
130 #else
131         if (!desc->chip->set_affinity(irq, cpumask)) {
132                 cpumask_copy(desc->affinity, cpumask);
133                 irq_set_thread_affinity(desc);
134         }
135 #endif
136         desc->status |= IRQ_AFFINITY_SET;
137         spin_unlock_irqrestore(&desc->lock, flags);
138         return 0;
139 }
140
141 #ifndef CONFIG_AUTO_IRQ_AFFINITY
142 /*
143  * Generic version of the affinity autoselector.
144  */
145 static int setup_affinity(unsigned int irq, struct irq_desc *desc)
146 {
147         if (!irq_can_set_affinity(irq))
148                 return 0;
149
150         /*
151          * Preserve an userspace affinity setup, but make sure that
152          * one of the targets is online.
153          */
154         if (desc->status & (IRQ_AFFINITY_SET | IRQ_NO_BALANCING)) {
155                 if (cpumask_any_and(desc->affinity, cpu_online_mask)
156                     < nr_cpu_ids)
157                         goto set_affinity;
158                 else
159                         desc->status &= ~IRQ_AFFINITY_SET;
160         }
161
162         cpumask_and(desc->affinity, cpu_online_mask, irq_default_affinity);
163 set_affinity:
164         desc->chip->set_affinity(irq, desc->affinity);
165
166         return 0;
167 }
168 #else
169 static inline int setup_affinity(unsigned int irq, struct irq_desc *d)
170 {
171         return irq_select_affinity(irq);
172 }
173 #endif
174
175 /*
176  * Called when affinity is set via /proc/irq
177  */
178 int irq_select_affinity_usr(unsigned int irq)
179 {
180         struct irq_desc *desc = irq_to_desc(irq);
181         unsigned long flags;
182         int ret;
183
184         spin_lock_irqsave(&desc->lock, flags);
185         ret = setup_affinity(irq, desc);
186         if (!ret)
187                 irq_set_thread_affinity(desc);
188         spin_unlock_irqrestore(&desc->lock, flags);
189
190         return ret;
191 }
192
193 #else
194 static inline int setup_affinity(unsigned int irq, struct irq_desc *desc)
195 {
196         return 0;
197 }
198 #endif
199
200 void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
201 {
202         if (suspend) {
203                 if (!desc->action || (desc->action->flags & IRQF_TIMER))
204                         return;
205                 desc->status |= IRQ_SUSPENDED;
206         }
207
208         if (!desc->depth++) {
209                 desc->status |= IRQ_DISABLED;
210                 desc->chip->disable(irq);
211         }
212 }
213
214 /**
215  *      disable_irq_nosync - disable an irq without waiting
216  *      @irq: Interrupt to disable
217  *
218  *      Disable the selected interrupt line.  Disables and Enables are
219  *      nested.
220  *      Unlike disable_irq(), this function does not ensure existing
221  *      instances of the IRQ handler have completed before returning.
222  *
223  *      This function may be called from IRQ context.
224  */
225 void disable_irq_nosync(unsigned int irq)
226 {
227         struct irq_desc *desc = irq_to_desc(irq);
228         unsigned long flags;
229
230         if (!desc)
231                 return;
232
233         spin_lock_irqsave(&desc->lock, flags);
234         __disable_irq(desc, irq, false);
235         spin_unlock_irqrestore(&desc->lock, flags);
236 }
237 EXPORT_SYMBOL(disable_irq_nosync);
238
239 /**
240  *      disable_irq - disable an irq and wait for completion
241  *      @irq: Interrupt to disable
242  *
243  *      Disable the selected interrupt line.  Enables and Disables are
244  *      nested.
245  *      This function waits for any pending IRQ handlers for this interrupt
246  *      to complete before returning. If you use this function while
247  *      holding a resource the IRQ handler may need you will deadlock.
248  *
249  *      This function may be called - with care - from IRQ context.
250  */
251 void disable_irq(unsigned int irq)
252 {
253         struct irq_desc *desc = irq_to_desc(irq);
254
255         if (!desc)
256                 return;
257
258         disable_irq_nosync(irq);
259         if (desc->action)
260                 synchronize_irq(irq);
261 }
262 EXPORT_SYMBOL(disable_irq);
263
264 void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
265 {
266         if (resume)
267                 desc->status &= ~IRQ_SUSPENDED;
268
269         switch (desc->depth) {
270         case 0:
271  err_out:
272                 WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
273                 break;
274         case 1: {
275                 unsigned int status = desc->status & ~IRQ_DISABLED;
276
277                 if (desc->status & IRQ_SUSPENDED)
278                         goto err_out;
279                 /* Prevent probing on this irq: */
280                 desc->status = status | IRQ_NOPROBE;
281                 check_irq_resend(desc, irq);
282                 /* fall-through */
283         }
284         default:
285                 desc->depth--;
286         }
287 }
288
289 /**
290  *      enable_irq - enable handling of an irq
291  *      @irq: Interrupt to enable
292  *
293  *      Undoes the effect of one call to disable_irq().  If this
294  *      matches the last disable, processing of interrupts on this
295  *      IRQ line is re-enabled.
296  *
297  *      This function may be called from IRQ context.
298  */
299 void enable_irq(unsigned int irq)
300 {
301         struct irq_desc *desc = irq_to_desc(irq);
302         unsigned long flags;
303
304         if (!desc)
305                 return;
306
307         spin_lock_irqsave(&desc->lock, flags);
308         __enable_irq(desc, irq, false);
309         spin_unlock_irqrestore(&desc->lock, flags);
310 }
311 EXPORT_SYMBOL(enable_irq);
312
313 static int set_irq_wake_real(unsigned int irq, unsigned int on)
314 {
315         struct irq_desc *desc = irq_to_desc(irq);
316         int ret = -ENXIO;
317
318         if (desc->chip->set_wake)
319                 ret = desc->chip->set_wake(irq, on);
320
321         return ret;
322 }
323
324 /**
325  *      set_irq_wake - control irq power management wakeup
326  *      @irq:   interrupt to control
327  *      @on:    enable/disable power management wakeup
328  *
329  *      Enable/disable power management wakeup mode, which is
330  *      disabled by default.  Enables and disables must match,
331  *      just as they match for non-wakeup mode support.
332  *
333  *      Wakeup mode lets this IRQ wake the system from sleep
334  *      states like "suspend to RAM".
335  */
336 int set_irq_wake(unsigned int irq, unsigned int on)
337 {
338         struct irq_desc *desc = irq_to_desc(irq);
339         unsigned long flags;
340         int ret = 0;
341
342         /* wakeup-capable irqs can be shared between drivers that
343          * don't need to have the same sleep mode behaviors.
344          */
345         spin_lock_irqsave(&desc->lock, flags);
346         if (on) {
347                 if (desc->wake_depth++ == 0) {
348                         ret = set_irq_wake_real(irq, on);
349                         if (ret)
350                                 desc->wake_depth = 0;
351                         else
352                                 desc->status |= IRQ_WAKEUP;
353                 }
354         } else {
355                 if (desc->wake_depth == 0) {
356                         WARN(1, "Unbalanced IRQ %d wake disable\n", irq);
357                 } else if (--desc->wake_depth == 0) {
358                         ret = set_irq_wake_real(irq, on);
359                         if (ret)
360                                 desc->wake_depth = 1;
361                         else
362                                 desc->status &= ~IRQ_WAKEUP;
363                 }
364         }
365
366         spin_unlock_irqrestore(&desc->lock, flags);
367         return ret;
368 }
369 EXPORT_SYMBOL(set_irq_wake);
370
371 /*
372  * Internal function that tells the architecture code whether a
373  * particular irq has been exclusively allocated or is available
374  * for driver use.
375  */
376 int can_request_irq(unsigned int irq, unsigned long irqflags)
377 {
378         struct irq_desc *desc = irq_to_desc(irq);
379         struct irqaction *action;
380
381         if (!desc)
382                 return 0;
383
384         if (desc->status & IRQ_NOREQUEST)
385                 return 0;
386
387         action = desc->action;
388         if (action)
389                 if (irqflags & action->flags & IRQF_SHARED)
390                         action = NULL;
391
392         return !action;
393 }
394
395 void compat_irq_chip_set_default_handler(struct irq_desc *desc)
396 {
397         /*
398          * If the architecture still has not overriden
399          * the flow handler then zap the default. This
400          * should catch incorrect flow-type setting.
401          */
402         if (desc->handle_irq == &handle_bad_irq)
403                 desc->handle_irq = NULL;
404 }
405
406 int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
407                 unsigned long flags)
408 {
409         int ret;
410         struct irq_chip *chip = desc->chip;
411
412         if (!chip || !chip->set_type) {
413                 /*
414                  * IRQF_TRIGGER_* but the PIC does not support multiple
415                  * flow-types?
416                  */
417                 pr_debug("No set_type function for IRQ %d (%s)\n", irq,
418                                 chip ? (chip->name ? : "unknown") : "unknown");
419                 return 0;
420         }
421
422         /* caller masked out all except trigger mode flags */
423         ret = chip->set_type(irq, flags);
424
425         if (ret)
426                 pr_err("setting trigger mode %d for irq %u failed (%pF)\n",
427                                 (int)flags, irq, chip->set_type);
428         else {
429                 if (flags & (IRQ_TYPE_LEVEL_LOW | IRQ_TYPE_LEVEL_HIGH))
430                         flags |= IRQ_LEVEL;
431                 /* note that IRQF_TRIGGER_MASK == IRQ_TYPE_SENSE_MASK */
432                 desc->status &= ~(IRQ_LEVEL | IRQ_TYPE_SENSE_MASK);
433                 desc->status |= flags;
434         }
435
436         return ret;
437 }
438
439 static int irq_wait_for_interrupt(struct irqaction *action)
440 {
441         while (!kthread_should_stop()) {
442                 set_current_state(TASK_INTERRUPTIBLE);
443
444                 if (test_and_clear_bit(IRQTF_RUNTHREAD,
445                                        &action->thread_flags)) {
446                         __set_current_state(TASK_RUNNING);
447                         return 0;
448                 }
449                 schedule();
450         }
451         return -1;
452 }
453
454 #ifdef CONFIG_SMP
455 /*
456  * Check whether we need to change the affinity of the interrupt thread.
457  */
458 static void
459 irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)
460 {
461         cpumask_var_t mask;
462
463         if (!test_and_clear_bit(IRQTF_AFFINITY, &action->thread_flags))
464                 return;
465
466         /*
467          * In case we are out of memory we set IRQTF_AFFINITY again and
468          * try again next time
469          */
470         if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
471                 set_bit(IRQTF_AFFINITY, &action->thread_flags);
472                 return;
473         }
474
475         spin_lock_irq(&desc->lock);
476         cpumask_copy(mask, desc->affinity);
477         spin_unlock_irq(&desc->lock);
478
479         set_cpus_allowed_ptr(current, mask);
480         free_cpumask_var(mask);
481 }
482 #else
483 static inline void
484 irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action) { }
485 #endif
486
487 /*
488  * Interrupt handler thread
489  */
490 static int irq_thread(void *data)
491 {
492         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2, };
493         struct irqaction *action = data;
494         struct irq_desc *desc = irq_to_desc(action->irq);
495         int wake;
496
497         sched_setscheduler(current, SCHED_FIFO, &param);
498         current->irqaction = action;
499
500         while (!irq_wait_for_interrupt(action)) {
501
502                 irq_thread_check_affinity(desc, action);
503
504                 atomic_inc(&desc->threads_active);
505
506                 spin_lock_irq(&desc->lock);
507                 if (unlikely(desc->status & IRQ_DISABLED)) {
508                         /*
509                          * CHECKME: We might need a dedicated
510                          * IRQ_THREAD_PENDING flag here, which
511                          * retriggers the thread in check_irq_resend()
512                          * but AFAICT IRQ_PENDING should be fine as it
513                          * retriggers the interrupt itself --- tglx
514                          */
515                         desc->status |= IRQ_PENDING;
516                         spin_unlock_irq(&desc->lock);
517                 } else {
518                         spin_unlock_irq(&desc->lock);
519
520                         action->thread_fn(action->irq, action->dev_id);
521                 }
522
523                 wake = atomic_dec_and_test(&desc->threads_active);
524
525                 if (wake && waitqueue_active(&desc->wait_for_threads))
526                         wake_up(&desc->wait_for_threads);
527         }
528
529         /*
530          * Clear irqaction. Otherwise exit_irq_thread() would make
531          * fuzz about an active irq thread going into nirvana.
532          */
533         current->irqaction = NULL;
534         return 0;
535 }
536
537 /*
538  * Called from do_exit()
539  */
540 void exit_irq_thread(void)
541 {
542         struct task_struct *tsk = current;
543
544         if (!tsk->irqaction)
545                 return;
546
547         printk(KERN_ERR
548                "exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
549                tsk->comm ? tsk->comm : "", tsk->pid, tsk->irqaction->irq);
550
551         /*
552          * Set the THREAD DIED flag to prevent further wakeups of the
553          * soon to be gone threaded handler.
554          */
555         set_bit(IRQTF_DIED, &tsk->irqaction->flags);
556 }
557
558 /*
559  * Internal function to register an irqaction - typically used to
560  * allocate special interrupts that are part of the architecture.
561  */
562 static int
563 __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
564 {
565         struct irqaction *old, **old_ptr;
566         const char *old_name = NULL;
567         unsigned long flags;
568         int shared = 0;
569         int ret;
570
571         if (!desc)
572                 return -EINVAL;
573
574         if (desc->chip == &no_irq_chip)
575                 return -ENOSYS;
576         /*
577          * Some drivers like serial.c use request_irq() heavily,
578          * so we have to be careful not to interfere with a
579          * running system.
580          */
581         if (new->flags & IRQF_SAMPLE_RANDOM) {
582                 /*
583                  * This function might sleep, we want to call it first,
584                  * outside of the atomic block.
585                  * Yes, this might clear the entropy pool if the wrong
586                  * driver is attempted to be loaded, without actually
587                  * installing a new handler, but is this really a problem,
588                  * only the sysadmin is able to do this.
589                  */
590                 rand_initialize_irq(irq);
591         }
592
593         /*
594          * Threaded handler ?
595          */
596         if (new->thread_fn) {
597                 struct task_struct *t;
598
599                 t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
600                                    new->name);
601                 if (IS_ERR(t))
602                         return PTR_ERR(t);
603                 /*
604                  * We keep the reference to the task struct even if
605                  * the thread dies to avoid that the interrupt code
606                  * references an already freed task_struct.
607                  */
608                 get_task_struct(t);
609                 new->thread = t;
610                 wake_up_process(t);
611         }
612
613         /*
614          * The following block of code has to be executed atomically
615          */
616         spin_lock_irqsave(&desc->lock, flags);
617         old_ptr = &desc->action;
618         old = *old_ptr;
619         if (old) {
620                 /*
621                  * Can't share interrupts unless both agree to and are
622                  * the same type (level, edge, polarity). So both flag
623                  * fields must have IRQF_SHARED set and the bits which
624                  * set the trigger type must match.
625                  */
626                 if (!((old->flags & new->flags) & IRQF_SHARED) ||
627                     ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
628                         old_name = old->name;
629                         goto mismatch;
630                 }
631
632 #if defined(CONFIG_IRQ_PER_CPU)
633                 /* All handlers must agree on per-cpuness */
634                 if ((old->flags & IRQF_PERCPU) !=
635                     (new->flags & IRQF_PERCPU))
636                         goto mismatch;
637 #endif
638
639                 /* add new interrupt at end of irq queue */
640                 do {
641                         old_ptr = &old->next;
642                         old = *old_ptr;
643                 } while (old);
644                 shared = 1;
645         }
646
647         if (!shared) {
648                 irq_chip_set_defaults(desc->chip);
649
650                 init_waitqueue_head(&desc->wait_for_threads);
651
652                 /* Setup the type (level, edge polarity) if configured: */
653                 if (new->flags & IRQF_TRIGGER_MASK) {
654                         ret = __irq_set_trigger(desc, irq,
655                                         new->flags & IRQF_TRIGGER_MASK);
656
657                         if (ret)
658                                 goto out_thread;
659                 } else
660                         compat_irq_chip_set_default_handler(desc);
661 #if defined(CONFIG_IRQ_PER_CPU)
662                 if (new->flags & IRQF_PERCPU)
663                         desc->status |= IRQ_PER_CPU;
664 #endif
665
666                 desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
667                                   IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
668
669                 if (!(desc->status & IRQ_NOAUTOEN)) {
670                         desc->depth = 0;
671                         desc->status &= ~IRQ_DISABLED;
672                         desc->chip->startup(irq);
673                 } else
674                         /* Undo nested disables: */
675                         desc->depth = 1;
676
677                 /* Exclude IRQ from balancing if requested */
678                 if (new->flags & IRQF_NOBALANCING)
679                         desc->status |= IRQ_NO_BALANCING;
680
681                 /* Set default affinity mask once everything is setup */
682                 setup_affinity(irq, desc);
683
684         } else if ((new->flags & IRQF_TRIGGER_MASK)
685                         && (new->flags & IRQF_TRIGGER_MASK)
686                                 != (desc->status & IRQ_TYPE_SENSE_MASK)) {
687                 /* hope the handler works with the actual trigger mode... */
688                 pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
689                                 irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
690                                 (int)(new->flags & IRQF_TRIGGER_MASK));
691         }
692
693         *old_ptr = new;
694
695         /* Reset broken irq detection when installing new handler */
696         desc->irq_count = 0;
697         desc->irqs_unhandled = 0;
698
699         /*
700          * Check whether we disabled the irq via the spurious handler
701          * before. Reenable it and give it another chance.
702          */
703         if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
704                 desc->status &= ~IRQ_SPURIOUS_DISABLED;
705                 __enable_irq(desc, irq, false);
706         }
707
708         spin_unlock_irqrestore(&desc->lock, flags);
709
710         new->irq = irq;
711         register_irq_proc(irq, desc);
712         new->dir = NULL;
713         register_handler_proc(irq, new);
714
715         return 0;
716
717 mismatch:
718 #ifdef CONFIG_DEBUG_SHIRQ
719         if (!(new->flags & IRQF_PROBE_SHARED)) {
720                 printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
721                 if (old_name)
722                         printk(KERN_ERR "current handler: %s\n", old_name);
723                 dump_stack();
724         }
725 #endif
726         ret = -EBUSY;
727
728 out_thread:
729         spin_unlock_irqrestore(&desc->lock, flags);
730         if (new->thread) {
731                 struct task_struct *t = new->thread;
732
733                 new->thread = NULL;
734                 if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
735                         kthread_stop(t);
736                 put_task_struct(t);
737         }
738         return ret;
739 }
740
741 /**
742  *      setup_irq - setup an interrupt
743  *      @irq: Interrupt line to setup
744  *      @act: irqaction for the interrupt
745  *
746  * Used to statically setup interrupts in the early boot process.
747  */
748 int setup_irq(unsigned int irq, struct irqaction *act)
749 {
750         struct irq_desc *desc = irq_to_desc(irq);
751
752         return __setup_irq(irq, desc, act);
753 }
754 EXPORT_SYMBOL_GPL(setup_irq);
755
756  /*
757  * Internal function to unregister an irqaction - used to free
758  * regular and special interrupts that are part of the architecture.
759  */
760 static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
761 {
762         struct irq_desc *desc = irq_to_desc(irq);
763         struct irqaction *action, **action_ptr;
764         struct task_struct *irqthread;
765         unsigned long flags;
766
767         WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
768
769         if (!desc)
770                 return NULL;
771
772         spin_lock_irqsave(&desc->lock, flags);
773
774         /*
775          * There can be multiple actions per IRQ descriptor, find the right
776          * one based on the dev_id:
777          */
778         action_ptr = &desc->action;
779         for (;;) {
780                 action = *action_ptr;
781
782                 if (!action) {
783                         WARN(1, "Trying to free already-free IRQ %d\n", irq);
784                         spin_unlock_irqrestore(&desc->lock, flags);
785
786                         return NULL;
787                 }
788
789                 if (action->dev_id == dev_id)
790                         break;
791                 action_ptr = &action->next;
792         }
793
794         /* Found it - now remove it from the list of entries: */
795         *action_ptr = action->next;
796
797         /* Currently used only by UML, might disappear one day: */
798 #ifdef CONFIG_IRQ_RELEASE_METHOD
799         if (desc->chip->release)
800                 desc->chip->release(irq, dev_id);
801 #endif
802
803         /* If this was the last handler, shut down the IRQ line: */
804         if (!desc->action) {
805                 desc->status |= IRQ_DISABLED;
806                 if (desc->chip->shutdown)
807                         desc->chip->shutdown(irq);
808                 else
809                         desc->chip->disable(irq);
810         }
811
812         irqthread = action->thread;
813         action->thread = NULL;
814
815         spin_unlock_irqrestore(&desc->lock, flags);
816
817         unregister_handler_proc(irq, action);
818
819         /* Make sure it's not being used on another CPU: */
820         synchronize_irq(irq);
821
822         if (irqthread) {
823                 if (!test_bit(IRQTF_DIED, &action->thread_flags))
824                         kthread_stop(irqthread);
825                 put_task_struct(irqthread);
826         }
827
828 #ifdef CONFIG_DEBUG_SHIRQ
829         /*
830          * It's a shared IRQ -- the driver ought to be prepared for an IRQ
831          * event to happen even now it's being freed, so let's make sure that
832          * is so by doing an extra call to the handler ....
833          *
834          * ( We do this after actually deregistering it, to make sure that a
835          *   'real' IRQ doesn't run in * parallel with our fake. )
836          */
837         if (action->flags & IRQF_SHARED) {
838                 local_irq_save(flags);
839                 action->handler(irq, dev_id);
840                 local_irq_restore(flags);
841         }
842 #endif
843         return action;
844 }
845
846 /**
847  *      remove_irq - free an interrupt
848  *      @irq: Interrupt line to free
849  *      @act: irqaction for the interrupt
850  *
851  * Used to remove interrupts statically setup by the early boot process.
852  */
853 void remove_irq(unsigned int irq, struct irqaction *act)
854 {
855         __free_irq(irq, act->dev_id);
856 }
857 EXPORT_SYMBOL_GPL(remove_irq);
858
859 /**
860  *      free_irq - free an interrupt allocated with request_irq
861  *      @irq: Interrupt line to free
862  *      @dev_id: Device identity to free
863  *
864  *      Remove an interrupt handler. The handler is removed and if the
865  *      interrupt line is no longer in use by any driver it is disabled.
866  *      On a shared IRQ the caller must ensure the interrupt is disabled
867  *      on the card it drives before calling this function. The function
868  *      does not return until any executing interrupts for this IRQ
869  *      have completed.
870  *
871  *      This function must not be called from interrupt context.
872  */
873 void free_irq(unsigned int irq, void *dev_id)
874 {
875         kfree(__free_irq(irq, dev_id));
876 }
877 EXPORT_SYMBOL(free_irq);
878
879 /**
880  *      request_threaded_irq - allocate an interrupt line
881  *      @irq: Interrupt line to allocate
882  *      @handler: Function to be called when the IRQ occurs.
883  *                Primary handler for threaded interrupts
884  *      @thread_fn: Function called from the irq handler thread
885  *                  If NULL, no irq thread is created
886  *      @irqflags: Interrupt type flags
887  *      @devname: An ascii name for the claiming device
888  *      @dev_id: A cookie passed back to the handler function
889  *
890  *      This call allocates interrupt resources and enables the
891  *      interrupt line and IRQ handling. From the point this
892  *      call is made your handler function may be invoked. Since
893  *      your handler function must clear any interrupt the board
894  *      raises, you must take care both to initialise your hardware
895  *      and to set up the interrupt handler in the right order.
896  *
897  *      If you want to set up a threaded irq handler for your device
898  *      then you need to supply @handler and @thread_fn. @handler ist
899  *      still called in hard interrupt context and has to check
900  *      whether the interrupt originates from the device. If yes it
901  *      needs to disable the interrupt on the device and return
902  *      IRQ_WAKE_THREAD which will wake up the handler thread and run
903  *      @thread_fn. This split handler design is necessary to support
904  *      shared interrupts.
905  *
906  *      Dev_id must be globally unique. Normally the address of the
907  *      device data structure is used as the cookie. Since the handler
908  *      receives this value it makes sense to use it.
909  *
910  *      If your interrupt is shared you must pass a non NULL dev_id
911  *      as this is required when freeing the interrupt.
912  *
913  *      Flags:
914  *
915  *      IRQF_SHARED             Interrupt is shared
916  *      IRQF_DISABLED   Disable local interrupts while processing
917  *      IRQF_SAMPLE_RANDOM      The interrupt can be used for entropy
918  *      IRQF_TRIGGER_*          Specify active edge(s) or level
919  *
920  */
921 int request_threaded_irq(unsigned int irq, irq_handler_t handler,
922                          irq_handler_t thread_fn, unsigned long irqflags,
923                          const char *devname, void *dev_id)
924 {
925         struct irqaction *action;
926         struct irq_desc *desc;
927         int retval;
928
929         /*
930          * handle_IRQ_event() always ignores IRQF_DISABLED except for
931          * the _first_ irqaction (sigh).  That can cause oopsing, but
932          * the behavior is classified as "will not fix" so we need to
933          * start nudging drivers away from using that idiom.
934          */
935         if ((irqflags & (IRQF_SHARED|IRQF_DISABLED)) ==
936                                         (IRQF_SHARED|IRQF_DISABLED)) {
937                 pr_warning(
938                   "IRQ %d/%s: IRQF_DISABLED is not guaranteed on shared IRQs\n",
939                         irq, devname);
940         }
941
942 #ifdef CONFIG_LOCKDEP
943         /*
944          * Lockdep wants atomic interrupt handlers:
945          */
946         irqflags |= IRQF_DISABLED;
947 #endif
948         /*
949          * Sanity-check: shared interrupts must pass in a real dev-ID,
950          * otherwise we'll have trouble later trying to figure out
951          * which interrupt is which (messes up the interrupt freeing
952          * logic etc).
953          */
954         if ((irqflags & IRQF_SHARED) && !dev_id)
955                 return -EINVAL;
956
957         desc = irq_to_desc(irq);
958         if (!desc)
959                 return -EINVAL;
960
961         if (desc->status & IRQ_NOREQUEST)
962                 return -EINVAL;
963         if (!handler)
964                 return -EINVAL;
965
966         action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
967         if (!action)
968                 return -ENOMEM;
969
970         action->handler = handler;
971         action->thread_fn = thread_fn;
972         action->flags = irqflags;
973         action->name = devname;
974         action->dev_id = dev_id;
975
976         retval = __setup_irq(irq, desc, action);
977         if (retval)
978                 kfree(action);
979
980 #ifdef CONFIG_DEBUG_SHIRQ
981         if (irqflags & IRQF_SHARED) {
982                 /*
983                  * It's a shared IRQ -- the driver ought to be prepared for it
984                  * to happen immediately, so let's make sure....
985                  * We disable the irq to make sure that a 'real' IRQ doesn't
986                  * run in parallel with our fake.
987                  */
988                 unsigned long flags;
989
990                 disable_irq(irq);
991                 local_irq_save(flags);
992
993                 handler(irq, dev_id);
994
995                 local_irq_restore(flags);
996                 enable_irq(irq);
997         }
998 #endif
999         return retval;
1000 }
1001 EXPORT_SYMBOL(request_threaded_irq);