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irq.c

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
 *    Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
 */

#include "linux/cpumask.h"
#include "linux/hardirq.h"
#include "linux/interrupt.h"
#include "linux/kernel_stat.h"
#include "linux/module.h"
#include "linux/seq_file.h"
#include "as-layout.h"
#include "kern_util.h"
#include "os.h"

/*
 * Generic, controller-independent functions:
 */

int show_interrupts(struct seq_file *p, void *v)
{
      int i = *(loff_t *) v, j;
      struct irqaction * action;
      unsigned long flags;

      if (i == 0) {
            seq_printf(p, "           ");
            for_each_online_cpu(j)
                  seq_printf(p, "CPU%d       ",j);
            seq_putc(p, '\n');
      }

      if (i < NR_IRQS) {
            spin_lock_irqsave(&irq_desc[i].lock, flags);
            action = irq_desc[i].action;
            if (!action)
                  goto skip;
            seq_printf(p, "%3d: ",i);
#ifndef CONFIG_SMP
            seq_printf(p, "%10u ", kstat_irqs(i));
#else
            for_each_online_cpu(j)
                  seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
#endif
            seq_printf(p, " %14s", irq_desc[i].chip->typename);
            seq_printf(p, "  %s", action->name);

            for (action=action->next; action; action = action->next)
                  seq_printf(p, ", %s", action->name);

            seq_putc(p, '\n');
skip:
            spin_unlock_irqrestore(&irq_desc[i].lock, flags);
      } else if (i == NR_IRQS)
            seq_putc(p, '\n');

      return 0;
}

/*
 * This list is accessed under irq_lock, except in sigio_handler,
 * where it is safe from being modified.  IRQ handlers won't change it -
 * if an IRQ source has vanished, it will be freed by free_irqs just
 * before returning from sigio_handler.  That will process a separate
 * list of irqs to free, with its own locking, coming back here to
 * remove list elements, taking the irq_lock to do so.
 */
static struct irq_fd *active_fds = NULL;
static struct irq_fd **last_irq_ptr = &active_fds;

extern void free_irqs(void);

void sigio_handler(int sig, struct uml_pt_regs *regs)
{
      struct irq_fd *irq_fd;
      int n;

      if (smp_sigio_handler())
            return;

      while (1) {
            n = os_waiting_for_events(active_fds);
            if (n <= 0) {
                  if (n == -EINTR)
                        continue;
                  else break;
            }

            for (irq_fd = active_fds; irq_fd != NULL;
                 irq_fd = irq_fd->next) {
                  if (irq_fd->current_events != 0) {
                        irq_fd->current_events = 0;
                        do_IRQ(irq_fd->irq, regs);
                  }
            }
      }

      free_irqs();
}

static DEFINE_SPINLOCK(irq_lock);

int activate_fd(int irq, int fd, int type, void *dev_id)
{
      struct pollfd *tmp_pfd;
      struct irq_fd *new_fd, *irq_fd;
      unsigned long flags;
      int pid, events, err, n;

      pid = os_getpid();
      err = os_set_fd_async(fd, pid);
      if (err < 0)
            goto out;

      err = -ENOMEM;
      new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
      if (new_fd == NULL)
            goto out;

      if (type == IRQ_READ)
            events = UM_POLLIN | UM_POLLPRI;
      else events = UM_POLLOUT;
      *new_fd = ((struct irq_fd) { .next              = NULL,
                             .id          = dev_id,
                             .fd          = fd,
                             .type        = type,
                             .irq         = irq,
                             .pid         = pid,
                             .events            = events,
                             .current_events    = 0 } );

      err = -EBUSY;
      spin_lock_irqsave(&irq_lock, flags);
      for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
            if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
                  printk(KERN_ERR "Registering fd %d twice\n", fd);
                  printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
                  printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
                         dev_id);
                  goto out_unlock;
            }
      }

      if (type == IRQ_WRITE)
            fd = -1;

      tmp_pfd = NULL;
      n = 0;

      while (1) {
            n = os_create_pollfd(fd, events, tmp_pfd, n);
            if (n == 0)
                  break;

            /*
             * n > 0
             * It means we couldn't put new pollfd to current pollfds
             * and tmp_fds is NULL or too small for new pollfds array.
             * Needed size is equal to n as minimum.
             *
             * Here we have to drop the lock in order to call
             * kmalloc, which might sleep.
             * If something else came in and changed the pollfds array
             * so we will not be able to put new pollfd struct to pollfds
             * then we free the buffer tmp_fds and try again.
             */
            spin_unlock_irqrestore(&irq_lock, flags);
            kfree(tmp_pfd);

            tmp_pfd = kmalloc(n, GFP_KERNEL);
            if (tmp_pfd == NULL)
                  goto out_kfree;

            spin_lock_irqsave(&irq_lock, flags);
      }

      *last_irq_ptr = new_fd;
      last_irq_ptr = &new_fd->next;

      spin_unlock_irqrestore(&irq_lock, flags);

      /*
       * This calls activate_fd, so it has to be outside the critical
       * section.
       */
      maybe_sigio_broken(fd, (type == IRQ_READ));

      return 0;

 out_unlock:
      spin_unlock_irqrestore(&irq_lock, flags);
 out_kfree:
      kfree(new_fd);
 out:
      return err;
}

static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
{
      unsigned long flags;

      spin_lock_irqsave(&irq_lock, flags);
      os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
      spin_unlock_irqrestore(&irq_lock, flags);
}

struct irq_and_dev {
      int irq;
      void *dev;
};

static int same_irq_and_dev(struct irq_fd *irq, void *d)
{
      struct irq_and_dev *data = d;

      return ((irq->irq == data->irq) && (irq->id == data->dev));
}

void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
{
      struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
                                            .dev  = dev });

      free_irq_by_cb(same_irq_and_dev, &data);
}

static int same_fd(struct irq_fd *irq, void *fd)
{
      return (irq->fd == *((int *)fd));
}

void free_irq_by_fd(int fd)
{
      free_irq_by_cb(same_fd, &fd);
}

/* Must be called with irq_lock held */
static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
{
      struct irq_fd *irq;
      int i = 0;
      int fdi;

      for (irq = active_fds; irq != NULL; irq = irq->next) {
            if ((irq->fd == fd) && (irq->irq == irqnum))
                  break;
            i++;
      }
      if (irq == NULL) {
            printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
                   fd);
            goto out;
      }
      fdi = os_get_pollfd(i);
      if ((fdi != -1) && (fdi != fd)) {
            printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
                   "and pollfds, fd %d vs %d, need %d\n", irq->fd,
                   fdi, fd);
            irq = NULL;
            goto out;
      }
      *index_out = i;
 out:
      return irq;
}

void reactivate_fd(int fd, int irqnum)
{
      struct irq_fd *irq;
      unsigned long flags;
      int i;

      spin_lock_irqsave(&irq_lock, flags);
      irq = find_irq_by_fd(fd, irqnum, &i);
      if (irq == NULL) {
            spin_unlock_irqrestore(&irq_lock, flags);
            return;
      }
      os_set_pollfd(i, irq->fd);
      spin_unlock_irqrestore(&irq_lock, flags);

      add_sigio_fd(fd);
}

void deactivate_fd(int fd, int irqnum)
{
      struct irq_fd *irq;
      unsigned long flags;
      int i;

      spin_lock_irqsave(&irq_lock, flags);
      irq = find_irq_by_fd(fd, irqnum, &i);
      if (irq == NULL) {
            spin_unlock_irqrestore(&irq_lock, flags);
            return;
      }

      os_set_pollfd(i, -1);
      spin_unlock_irqrestore(&irq_lock, flags);

      ignore_sigio_fd(fd);
}

/*
 * Called just before shutdown in order to provide a clean exec
 * environment in case the system is rebooting.  No locking because
 * that would cause a pointless shutdown hang if something hadn't
 * released the lock.
 */
int deactivate_all_fds(void)
{
      struct irq_fd *irq;
      int err;

      for (irq = active_fds; irq != NULL; irq = irq->next) {
            err = os_clear_fd_async(irq->fd);
            if (err)
                  return err;
      }
      /* If there is a signal already queued, after unblocking ignore it */
      os_set_ioignore();

      return 0;
}

/*
 * do_IRQ handles all normal device IRQs (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
{
      struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
      irq_enter();
      __do_IRQ(irq);
      irq_exit();
      set_irq_regs(old_regs);
      return 1;
}

int um_request_irq(unsigned int irq, int fd, int type,
               irq_handler_t handler,
               unsigned long irqflags, const char * devname,
               void *dev_id)
{
      int err;

      if (fd != -1) {
            err = activate_fd(irq, fd, type, dev_id);
            if (err)
                  return err;
      }

      return request_irq(irq, handler, irqflags, devname, dev_id);
}

EXPORT_SYMBOL(um_request_irq);
EXPORT_SYMBOL(reactivate_fd);

/*
 * hw_interrupt_type must define (startup || enable) &&
 * (shutdown || disable) && end
 */
static void dummy(unsigned int irq)
{
}

/* This is used for everything else than the timer. */
static struct hw_interrupt_type normal_irq_type = {
      .typename = "SIGIO",
      .release = free_irq_by_irq_and_dev,
      .disable = dummy,
      .enable = dummy,
      .ack = dummy,
      .end = dummy
};

static struct hw_interrupt_type SIGVTALRM_irq_type = {
      .typename = "SIGVTALRM",
      .release = free_irq_by_irq_and_dev,
      .shutdown = dummy, /* never called */
      .disable = dummy,
      .enable = dummy,
      .ack = dummy,
      .end = dummy
};

void __init init_IRQ(void)
{
      int i;

      irq_desc[TIMER_IRQ].status = IRQ_DISABLED;
      irq_desc[TIMER_IRQ].action = NULL;
      irq_desc[TIMER_IRQ].depth = 1;
      irq_desc[TIMER_IRQ].chip = &SIGVTALRM_irq_type;
      enable_irq(TIMER_IRQ);
      for (i = 1; i < NR_IRQS; i++) {
            irq_desc[i].status = IRQ_DISABLED;
            irq_desc[i].action = NULL;
            irq_desc[i].depth = 1;
            irq_desc[i].chip = &normal_irq_type;
            enable_irq(i);
      }
}

int init_aio_irq(int irq, char *name, irq_handler_t handler)
{
      int fds[2], err;

      err = os_pipe(fds, 1, 1);
      if (err) {
            printk(KERN_ERR "init_aio_irq - os_pipe failed, err = %d\n",
                   -err);
            goto out;
      }

      err = um_request_irq(irq, fds[0], IRQ_READ, handler,
                       IRQF_DISABLED | IRQF_SAMPLE_RANDOM, name,
                       (void *) (long) fds[0]);
      if (err) {
            printk(KERN_ERR "init_aio_irq - : um_request_irq failed, "
                   "err = %d\n",
                   err);
            goto out_close;
      }

      err = fds[1];
      goto out;

 out_close:
      os_close_file(fds[0]);
      os_close_file(fds[1]);
 out:
      return err;
}

/*
 * IRQ stack entry and exit:
 *
 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
 * and switch over to the IRQ stack after some preparation.  We use
 * sigaltstack to receive signals on a separate stack from the start.
 * These two functions make sure the rest of the kernel won't be too
 * upset by being on a different stack.  The IRQ stack has a
 * thread_info structure at the bottom so that current et al continue
 * to work.
 *
 * to_irq_stack copies the current task's thread_info to the IRQ stack
 * thread_info and sets the tasks's stack to point to the IRQ stack.
 *
 * from_irq_stack copies the thread_info struct back (flags may have
 * been modified) and resets the task's stack pointer.
 *
 * Tricky bits -
 *
 * What happens when two signals race each other?  UML doesn't block
 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
 * could arrive while a previous one is still setting up the
 * thread_info.
 *
 * There are three cases -
 *     The first interrupt on the stack - sets up the thread_info and
 * handles the interrupt
 *     A nested interrupt interrupting the copying of the thread_info -
 * can't handle the interrupt, as the stack is in an unknown state
 *     A nested interrupt not interrupting the copying of the
 * thread_info - doesn't do any setup, just handles the interrupt
 *
 * The first job is to figure out whether we interrupted stack setup.
 * This is done by xchging the signal mask with thread_info->pending.
 * If the value that comes back is zero, then there is no setup in
 * progress, and the interrupt can be handled.  If the value is
 * non-zero, then there is stack setup in progress.  In order to have
 * the interrupt handled, we leave our signal in the mask, and it will
 * be handled by the upper handler after it has set up the stack.
 *
 * Next is to figure out whether we are the outer handler or a nested
 * one.  As part of setting up the stack, thread_info->real_thread is
 * set to non-NULL (and is reset to NULL on exit).  This is the
 * nesting indicator.  If it is non-NULL, then the stack is already
 * set up and the handler can run.
 */

static unsigned long pending_mask;

unsigned long to_irq_stack(unsigned long *mask_out)
{
      struct thread_info *ti;
      unsigned long mask, old;
      int nested;

      mask = xchg(&pending_mask, *mask_out);
      if (mask != 0) {
            /*
             * If any interrupts come in at this point, we want to
             * make sure that their bits aren't lost by our
             * putting our bit in.  So, this loop accumulates bits
             * until xchg returns the same value that we put in.
             * When that happens, there were no new interrupts,
             * and pending_mask contains a bit for each interrupt
             * that came in.
             */
            old = *mask_out;
            do {
                  old |= mask;
                  mask = xchg(&pending_mask, old);
            } while (mask != old);
            return 1;
      }

      ti = current_thread_info();
      nested = (ti->real_thread != NULL);
      if (!nested) {
            struct task_struct *task;
            struct thread_info *tti;

            task = cpu_tasks[ti->cpu].task;
            tti = task_thread_info(task);

            *ti = *tti;
            ti->real_thread = tti;
            task->stack = ti;
      }

      mask = xchg(&pending_mask, 0);
      *mask_out |= mask | nested;
      return 0;
}

unsigned long from_irq_stack(int nested)
{
      struct thread_info *ti, *to;
      unsigned long mask;

      ti = current_thread_info();

      pending_mask = 1;

      to = ti->real_thread;
      current->stack = to;
      ti->real_thread = NULL;
      *to = *ti;

      mask = xchg(&pending_mask, 0);
      return mask & ~1;
}


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