arch/um/kernel/irq.c

   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  */
  28 static struct irq_fd *active_fds = NULL;
  29 static struct irq_fd **last_irq_ptr = &active_fds;
  30
  31 extern void free_irqs(void);
  32
  33 void 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
  61 static DEFINE_SPINLOCK(irq_lock);
  62
  63 static 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
 156 static 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
 165 struct irq_and_dev {
 166         int irq;
 167         void *dev;
 168 };
 169
 170 static 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
 177 static 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
 185 static int same_fd(struct irq_fd *irq, void *fd)
 186 {
 187         return (irq->fd == *((int *)fd));
 188 }
 189
 190 void 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 */
 196 static 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
 225 void 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
 243 void 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 }
 261 EXPORT_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  */
 269 int 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  */
 290 unsigned 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
 300 int 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
 316 EXPORT_SYMBOL(um_request_irq);
 317 EXPORT_SYMBOL(reactivate_fd);
 318
 319 /*
 320  * irq_chip must define at least enable/disable and ack when
 321  * the edge handler is used.
 322  */
 323 static void dummy(struct irq_data *d)
 324 {
 325 }
 326
 327 /* This is used for everything else than the timer. */
 328 static 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
 336 static 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
 344 void __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
 401 static unsigned long pending_mask;
 402
 403 unsigned 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
 447 unsigned 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