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