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