linux/arch/um/kernel/irq.c
<<
>>
Prefs
   1/*
   2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3 * Licensed under the GPL
   4 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
   5 *      Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
   6 */
   7
   8#include "linux/cpumask.h"
   9#include "linux/hardirq.h"
  10#include "linux/interrupt.h"
  11#include "linux/kernel_stat.h"
  12#include "linux/module.h"
  13#include "linux/sched.h"
  14#include "linux/seq_file.h"
  15#include "linux/slab.h"
  16#include "as-layout.h"
  17#include "kern_util.h"
  18#include "os.h"
  19
  20/*
  21 * This list is accessed under irq_lock, except in sigio_handler,
  22 * where it is safe from being modified.  IRQ handlers won't change it -
  23 * if an IRQ source has vanished, it will be freed by free_irqs just
  24 * before returning from sigio_handler.  That will process a separate
  25 * list of irqs to free, with its own locking, coming back here to
  26 * remove list elements, taking the irq_lock to do so.
  27 */
  28static struct irq_fd *active_fds = NULL;
  29static struct irq_fd **last_irq_ptr = &active_fds;
  30
  31extern void free_irqs(void);
  32
  33void sigio_handler(int sig, struct uml_pt_regs *regs)
  34{
  35        struct irq_fd *irq_fd;
  36        int n;
  37
  38        if (smp_sigio_handler())
  39                return;
  40
  41        while (1) {
  42                n = os_waiting_for_events(active_fds);
  43                if (n <= 0) {
  44                        if (n == -EINTR)
  45                                continue;
  46                        else break;
  47                }
  48
  49                for (irq_fd = active_fds; irq_fd != NULL;
  50                     irq_fd = irq_fd->next) {
  51                        if (irq_fd->current_events != 0) {
  52                                irq_fd->current_events = 0;
  53                                do_IRQ(irq_fd->irq, regs);
  54                        }
  55                }
  56        }
  57
  58        free_irqs();
  59}
  60
  61static DEFINE_SPINLOCK(irq_lock);
  62
  63static int activate_fd(int irq, int fd, int type, void *dev_id)
  64{
  65        struct pollfd *tmp_pfd;
  66        struct irq_fd *new_fd, *irq_fd;
  67        unsigned long flags;
  68        int events, err, n;
  69
  70        err = os_set_fd_async(fd);
  71        if (err < 0)
  72                goto out;
  73
  74        err = -ENOMEM;
  75        new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
  76        if (new_fd == NULL)
  77                goto out;
  78
  79        if (type == IRQ_READ)
  80                events = UM_POLLIN | UM_POLLPRI;
  81        else events = UM_POLLOUT;
  82        *new_fd = ((struct irq_fd) { .next              = NULL,
  83                                     .id                = dev_id,
  84                                     .fd                = fd,
  85                                     .type              = type,
  86                                     .irq               = irq,
  87                                     .events            = events,
  88                                     .current_events    = 0 } );
  89
  90        err = -EBUSY;
  91        spin_lock_irqsave(&irq_lock, flags);
  92        for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
  93                if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
  94                        printk(KERN_ERR "Registering fd %d twice\n", fd);
  95                        printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
  96                        printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
  97                               dev_id);
  98                        goto out_unlock;
  99                }
 100        }
 101
 102        if (type == IRQ_WRITE)
 103                fd = -1;
 104
 105        tmp_pfd = NULL;
 106        n = 0;
 107
 108        while (1) {
 109                n = os_create_pollfd(fd, events, tmp_pfd, n);
 110                if (n == 0)
 111                        break;
 112
 113                /*
 114                 * n > 0
 115                 * It means we couldn't put new pollfd to current pollfds
 116                 * and tmp_fds is NULL or too small for new pollfds array.
 117                 * Needed size is equal to n as minimum.
 118                 *
 119                 * Here we have to drop the lock in order to call
 120                 * kmalloc, which might sleep.
 121                 * If something else came in and changed the pollfds array
 122                 * so we will not be able to put new pollfd struct to pollfds
 123                 * then we free the buffer tmp_fds and try again.
 124                 */
 125                spin_unlock_irqrestore(&irq_lock, flags);
 126                kfree(tmp_pfd);
 127
 128                tmp_pfd = kmalloc(n, GFP_KERNEL);
 129                if (tmp_pfd == NULL)
 130                        goto out_kfree;
 131
 132                spin_lock_irqsave(&irq_lock, flags);
 133        }
 134
 135        *last_irq_ptr = new_fd;
 136        last_irq_ptr = &new_fd->next;
 137
 138        spin_unlock_irqrestore(&irq_lock, flags);
 139
 140        /*
 141         * This calls activate_fd, so it has to be outside the critical
 142         * section.
 143         */
 144        maybe_sigio_broken(fd, (type == IRQ_READ));
 145
 146        return 0;
 147
 148 out_unlock:
 149        spin_unlock_irqrestore(&irq_lock, flags);
 150 out_kfree:
 151        kfree(new_fd);
 152 out:
 153        return err;
 154}
 155
 156static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
 157{
 158        unsigned long flags;
 159
 160        spin_lock_irqsave(&irq_lock, flags);
 161        os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
 162        spin_unlock_irqrestore(&irq_lock, flags);
 163}
 164
 165struct irq_and_dev {
 166        int irq;
 167        void *dev;
 168};
 169
 170static int same_irq_and_dev(struct irq_fd *irq, void *d)
 171{
 172        struct irq_and_dev *data = d;
 173
 174        return ((irq->irq == data->irq) && (irq->id == data->dev));
 175}
 176
 177static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 178{
 179        struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
 180                                                          .dev  = dev });
 181
 182        free_irq_by_cb(same_irq_and_dev, &data);
 183}
 184
 185static int same_fd(struct irq_fd *irq, void *fd)
 186{
 187        return (irq->fd == *((int *)fd));
 188}
 189
 190void free_irq_by_fd(int fd)
 191{
 192        free_irq_by_cb(same_fd, &fd);
 193}
 194
 195/* Must be called with irq_lock held */
 196static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
 197{
 198        struct irq_fd *irq;
 199        int i = 0;
 200        int fdi;
 201
 202        for (irq = active_fds; irq != NULL; irq = irq->next) {
 203                if ((irq->fd == fd) && (irq->irq == irqnum))
 204                        break;
 205                i++;
 206        }
 207        if (irq == NULL) {
 208                printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
 209                       fd);
 210                goto out;
 211        }
 212        fdi = os_get_pollfd(i);
 213        if ((fdi != -1) && (fdi != fd)) {
 214                printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
 215                       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
 216                       fdi, fd);
 217                irq = NULL;
 218                goto out;
 219        }
 220        *index_out = i;
 221 out:
 222        return irq;
 223}
 224
 225void reactivate_fd(int fd, int irqnum)
 226{
 227        struct irq_fd *irq;
 228        unsigned long flags;
 229        int i;
 230
 231        spin_lock_irqsave(&irq_lock, flags);
 232        irq = find_irq_by_fd(fd, irqnum, &i);
 233        if (irq == NULL) {
 234                spin_unlock_irqrestore(&irq_lock, flags);
 235                return;
 236        }
 237        os_set_pollfd(i, irq->fd);
 238        spin_unlock_irqrestore(&irq_lock, flags);
 239
 240        add_sigio_fd(fd);
 241}
 242
 243void deactivate_fd(int fd, int irqnum)
 244{
 245        struct irq_fd *irq;
 246        unsigned long flags;
 247        int i;
 248
 249        spin_lock_irqsave(&irq_lock, flags);
 250        irq = find_irq_by_fd(fd, irqnum, &i);
 251        if (irq == NULL) {
 252                spin_unlock_irqrestore(&irq_lock, flags);
 253                return;
 254        }
 255
 256        os_set_pollfd(i, -1);
 257        spin_unlock_irqrestore(&irq_lock, flags);
 258
 259        ignore_sigio_fd(fd);
 260}
 261EXPORT_SYMBOL(deactivate_fd);
 262
 263/*
 264 * Called just before shutdown in order to provide a clean exec
 265 * environment in case the system is rebooting.  No locking because
 266 * that would cause a pointless shutdown hang if something hadn't
 267 * released the lock.
 268 */
 269int deactivate_all_fds(void)
 270{
 271        struct irq_fd *irq;
 272        int err;
 273
 274        for (irq = active_fds; irq != NULL; irq = irq->next) {
 275                err = os_clear_fd_async(irq->fd);
 276                if (err)
 277                        return err;
 278        }
 279        /* If there is a signal already queued, after unblocking ignore it */
 280        os_set_ioignore();
 281
 282        return 0;
 283}
 284
 285/*
 286 * do_IRQ handles all normal device IRQs (the special
 287 * SMP cross-CPU interrupts have their own specific
 288 * handlers).
 289 */
 290unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
 291{
 292        struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
 293        irq_enter();
 294        generic_handle_irq(irq);
 295        irq_exit();
 296        set_irq_regs(old_regs);
 297        return 1;
 298}
 299
 300int um_request_irq(unsigned int irq, int fd, int type,
 301                   irq_handler_t handler,
 302                   unsigned long irqflags, const char * devname,
 303                   void *dev_id)
 304{
 305        int err;
 306
 307        if (fd != -1) {
 308                err = activate_fd(irq, fd, type, dev_id);
 309                if (err)
 310                        return err;
 311        }
 312
 313        return request_irq(irq, handler, irqflags, devname, dev_id);
 314}
 315
 316EXPORT_SYMBOL(um_request_irq);
 317EXPORT_SYMBOL(reactivate_fd);
 318
 319/*
 320 * irq_chip must define at least enable/disable and ack when
 321 * the edge handler is used.
 322 */
 323static void dummy(struct irq_data *d)
 324{
 325}
 326
 327/* This is used for everything else than the timer. */
 328static struct irq_chip normal_irq_type = {
 329        .name = "SIGIO",
 330        .release = free_irq_by_irq_and_dev,
 331        .irq_disable = dummy,
 332        .irq_enable = dummy,
 333        .irq_ack = dummy,
 334};
 335
 336static struct irq_chip SIGVTALRM_irq_type = {
 337        .name = "SIGVTALRM",
 338        .release = free_irq_by_irq_and_dev,
 339        .irq_disable = dummy,
 340        .irq_enable = dummy,
 341        .irq_ack = dummy,
 342};
 343
 344void __init init_IRQ(void)
 345{
 346        int i;
 347
 348        irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 349
 350        for (i = 1; i < NR_IRQS; i++)
 351                irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
 352}
 353
 354/*
 355 * IRQ stack entry and exit:
 356 *
 357 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
 358 * and switch over to the IRQ stack after some preparation.  We use
 359 * sigaltstack to receive signals on a separate stack from the start.
 360 * These two functions make sure the rest of the kernel won't be too
 361 * upset by being on a different stack.  The IRQ stack has a
 362 * thread_info structure at the bottom so that current et al continue
 363 * to work.
 364 *
 365 * to_irq_stack copies the current task's thread_info to the IRQ stack
 366 * thread_info and sets the tasks's stack to point to the IRQ stack.
 367 *
 368 * from_irq_stack copies the thread_info struct back (flags may have
 369 * been modified) and resets the task's stack pointer.
 370 *
 371 * Tricky bits -
 372 *
 373 * What happens when two signals race each other?  UML doesn't block
 374 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
 375 * could arrive while a previous one is still setting up the
 376 * thread_info.
 377 *
 378 * There are three cases -
 379 *     The first interrupt on the stack - sets up the thread_info and
 380 * handles the interrupt
 381 *     A nested interrupt interrupting the copying of the thread_info -
 382 * can't handle the interrupt, as the stack is in an unknown state
 383 *     A nested interrupt not interrupting the copying of the
 384 * thread_info - doesn't do any setup, just handles the interrupt
 385 *
 386 * The first job is to figure out whether we interrupted stack setup.
 387 * This is done by xchging the signal mask with thread_info->pending.
 388 * If the value that comes back is zero, then there is no setup in
 389 * progress, and the interrupt can be handled.  If the value is
 390 * non-zero, then there is stack setup in progress.  In order to have
 391 * the interrupt handled, we leave our signal in the mask, and it will
 392 * be handled by the upper handler after it has set up the stack.
 393 *
 394 * Next is to figure out whether we are the outer handler or a nested
 395 * one.  As part of setting up the stack, thread_info->real_thread is
 396 * set to non-NULL (and is reset to NULL on exit).  This is the
 397 * nesting indicator.  If it is non-NULL, then the stack is already
 398 * set up and the handler can run.
 399 */
 400
 401static unsigned long pending_mask;
 402
 403unsigned long to_irq_stack(unsigned long *mask_out)
 404{
 405        struct thread_info *ti;
 406        unsigned long mask, old;
 407        int nested;
 408
 409        mask = xchg(&pending_mask, *mask_out);
 410        if (mask != 0) {
 411                /*
 412                 * If any interrupts come in at this point, we want to
 413                 * make sure that their bits aren't lost by our
 414                 * putting our bit in.  So, this loop accumulates bits
 415                 * until xchg returns the same value that we put in.
 416                 * When that happens, there were no new interrupts,
 417                 * and pending_mask contains a bit for each interrupt
 418                 * that came in.
 419                 */
 420                old = *mask_out;
 421                do {
 422                        old |= mask;
 423                        mask = xchg(&pending_mask, old);
 424                } while (mask != old);
 425                return 1;
 426        }
 427
 428        ti = current_thread_info();
 429        nested = (ti->real_thread != NULL);
 430        if (!nested) {
 431                struct task_struct *task;
 432                struct thread_info *tti;
 433
 434                task = cpu_tasks[ti->cpu].task;
 435                tti = task_thread_info(task);
 436
 437                *ti = *tti;
 438                ti->real_thread = tti;
 439                task->stack = ti;
 440        }
 441
 442        mask = xchg(&pending_mask, 0);
 443        *mask_out |= mask | nested;
 444        return 0;
 445}
 446
 447unsigned long from_irq_stack(int nested)
 448{
 449        struct thread_info *ti, *to;
 450        unsigned long mask;
 451
 452        ti = current_thread_info();
 453
 454        pending_mask = 1;
 455
 456        to = ti->real_thread;
 457        current->stack = to;
 458        ti->real_thread = NULL;
 459        *to = *ti;
 460
 461        mask = xchg(&pending_mask, 0);
 462        return mask & ~1;
 463}
 464
 465
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.