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