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glibc  2.9
Functions | Variables
setitimer.c File Reference
#include <stddef.h>
#include <errno.h>
#include <sys/time.h>
#include <time.h>
#include <hurd.h>
#include <hurd/signal.h>
#include <hurd/sigpreempt.h>
#include <hurd/msg_request.h>
#include <mach/message.h>

Go to the source code of this file.

Functions

static void quantize_timeval (struct timeval *tv)
static void subtract_timeval (struct timeval *from, const struct timeval *subtract)
static void timer_thread (void)
static int setitimer_locked (const struct itimerval *new, struct itimerval *old, void *crit)
static sighandler_t restart_itimer (struct hurd_signal_preemptor *preemptor, struct hurd_sigstate *ss, int *signo, struct hurd_signal_detail *detail)
int __setitimer (enum __itimer_which which, const struct itimerval *new, struct itimerval *old)
static void fork_itimer (void)
 text_set_element (_hurd_fork_child_hook, fork_itimer)

Variables

spin_lock_t _hurd_itimer_lock = SPIN_LOCK_INITIALIZER
mach_port_t _hurd_itimer_port
thread_t _hurd_itimer_thread
int _hurd_itimer_thread_suspended
vm_address_t _hurd_itimer_thread_stack_base
vm_address_t _hurd_itimer_thread_stack_size

Function Documentation

int __setitimer ( enum __itimer_which  which,
const struct itimerval new,
struct itimerval old 
)

Definition at line 333 of file setitimer.c.

{
  void *crit;

  switch (which)
    {
    default:
      return __hurd_fail (EINVAL);

    case ITIMER_VIRTUAL:
    case ITIMER_PROF:
      return __hurd_fail (ENOSYS);

    case ITIMER_REAL:
      break;
    }

  crit = _hurd_critical_section_lock ();
  __spin_lock (&_hurd_itimer_lock);
  return setitimer_locked (new, old, crit);
}

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static void fork_itimer ( void  ) [static]

Definition at line 357 of file setitimer.c.

{
  /* We must restart the itimer in the child.  */

  struct itimerval it;

  __spin_lock (&_hurd_itimer_lock);
  _hurd_itimer_thread = MACH_PORT_NULL;
  it = _hurd_itimerval;
  it.it_value = it.it_interval;

  setitimer_locked (&it, NULL, NULL);

  (void) &fork_itimer;             /* Avoid gcc optimizing out the function.  */
}

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static void quantize_timeval ( struct timeval tv) [static]

Definition at line 42 of file setitimer.c.

{
  static time_t quantum = -1;

  if (quantum == -1)
    quantum = 1000000 / __getclktck ();

  tv->tv_usec = ((tv->tv_usec + (quantum - 1)) / quantum) * quantum;
  if (tv->tv_usec >= 1000000)
    {
      ++tv->tv_sec;
      tv->tv_usec -= 1000000;
    }
}

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static sighandler_t restart_itimer ( struct hurd_signal_preemptor preemptor,
struct hurd_sigstate ss,
int signo,
struct hurd_signal_detail detail 
) [static]

Definition at line 136 of file setitimer.c.

{
  /* This function gets called in the signal thread
     each time a SIGALRM is arriving (even if blocked).  */
  struct itimerval it;

  /* Either reload or disable the itimer.  */
  __spin_lock (&_hurd_itimer_lock);
  it.it_value = it.it_interval = _hurd_itimerval.it_interval;
  setitimer_locked (&it, NULL, NULL);

  /* Continue with normal delivery (or hold, etc.) of SIGALRM.  */
  return SIG_ERR;
}

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static int setitimer_locked ( const struct itimerval new,
struct itimerval old,
void *  crit 
) [static]

Definition at line 158 of file setitimer.c.

{
  struct itimerval newval;
  struct timeval now, remaining, elapsed;
  struct timeval old_interval;
  error_t err;

  inline void kill_itimer_thread (void)
    {
      __thread_terminate (_hurd_itimer_thread);
      __vm_deallocate (__mach_task_self (),
                     _hurd_itimer_thread_stack_base,
                     _hurd_itimer_thread_stack_size);
      _hurd_itimer_thread = MACH_PORT_NULL;
    }

  if (!new)
    {
      /* Just return the current value in OLD without changing anything.
        This is what BSD does, even though it's not documented. */
      if (old)
       *old = _hurd_itimerval;
      spin_unlock (&_hurd_itimer_lock);
      _hurd_critical_section_unlock (crit);
      return 0;
    }

  newval = *new;
  quantize_timeval (&newval.it_interval);
  quantize_timeval (&newval.it_value);
  if ((newval.it_value.tv_sec | newval.it_value.tv_usec) != 0)
    {
      /* Make sure the itimer thread is set up.  */

      /* Set up a signal preemptor global for all threads to
        run `restart_itimer' each time a SIGALRM would arrive.  */
      static struct hurd_signal_preemptor preemptor =
       {
         __sigmask (SIGALRM), 0, 0,
         &restart_itimer,
       };
      __mutex_lock (&_hurd_siglock);
      if (! preemptor.next && _hurdsig_preemptors != &preemptor)
       {
         preemptor.next = _hurdsig_preemptors;
         _hurdsig_preemptors = &preemptor;
       }
      __mutex_unlock (&_hurd_siglock);

      if (_hurd_itimer_port == MACH_PORT_NULL)
       {
         /* Allocate a receive right that the itimer thread will
            block waiting for a message on.  */
         if (err = __mach_port_allocate (__mach_task_self (),
                                     MACH_PORT_RIGHT_RECEIVE,
                                     &_hurd_itimer_port))
           goto out;
       }

      if (_hurd_itimer_thread == MACH_PORT_NULL)
       {
         /* Start up the itimer thread running `timer_thread' (below).  */
         if (err = __thread_create (__mach_task_self (),
                                 &_hurd_itimer_thread))
           return __hurd_fail (err);
         _hurd_itimer_thread_stack_base = 0; /* Anywhere.  */
         _hurd_itimer_thread_stack_size = __vm_page_size; /* Small stack.  */
         if (err = __mach_setup_thread (__mach_task_self (),
                                    _hurd_itimer_thread,
                                    &timer_thread,
                                    &_hurd_itimer_thread_stack_base,
                                    &_hurd_itimer_thread_stack_size))
           {
             __thread_terminate (_hurd_itimer_thread);
             _hurd_itimer_thread = MACH_PORT_NULL;
             goto out;
           }
         _hurd_itimer_thread_suspended = 1;
       }
    }

  if ((newval.it_value.tv_sec | newval.it_value.tv_usec) != 0 || old != NULL)
    {
      /* Calculate how much time is remaining for the pending alarm.  */
      if (__gettimeofday (&now, NULL) < 0)
       {
         __spin_unlock (&_hurd_itimer_lock);
         _hurd_critical_section_unlock (crit);
         return -1;
       }
      elapsed = now;
      subtract_timeval (&elapsed, &_hurd_itimer_started);
      remaining = _hurd_itimerval.it_value;
      if (timercmp (&remaining, &elapsed, <))
       {
         /* Hmm.  The timer should have just gone off, but has not been reset.
            This is a possible timing glitch.  The alarm will signal soon. */
         /* XXX wrong */
         remaining.tv_sec = 0;
         remaining.tv_usec = 0;
       }
      else
       subtract_timeval (&remaining, &elapsed);

      /* Remember the old reload interval before changing it.  */
      old_interval = _hurd_itimerval.it_interval;

      /* Record the starting time that the timer interval relates to.  */
      _hurd_itimer_started = now;
    }

  /* Load the new itimer value.  */
  _hurd_itimerval = newval;

  if ((newval.it_value.tv_sec | newval.it_value.tv_usec) == 0)
    {
      /* Disable the itimer.  */
      if (_hurd_itimer_thread && !_hurd_itimer_thread_suspended)
       {
         /* Suspend the itimer thread so it does nothing.  Then abort its
            kernel context so that when the thread is resumed, mach_msg
            will return to timer_thread (below) and it will fetch new
            values from _hurd_itimerval.  */
         if ((err = __thread_suspend (_hurd_itimer_thread)) ||
             (err = __thread_abort (_hurd_itimer_thread)))
           /* If we can't save it for later, nuke it.  */
           kill_itimer_thread ();
         else
           _hurd_itimer_thread_suspended = 1;
       }
    }
  /* See if the timeout changed.  If so, we must alert the itimer thread.  */
  else if (remaining.tv_sec != newval.it_value.tv_sec ||
          remaining.tv_usec != newval.it_value.tv_usec)
    {
      /* The timeout value is changing.  Tell the itimer thread to
        reexamine it and start counting down.  If the itimer thread is
        marked as suspended, either we just created it, or it was
        suspended and thread_abort'd last time the itimer was disabled;
        either way it will wake up and start waiting for the new timeout
        value when we resume it.  If it is not suspended, the itimer
        thread is waiting to deliver a pending alarm that we will override
        (since it would come later than the new alarm being set);
        thread_abort will make mach_msg return MACH_RCV_INTERRUPTED, so it
        will loop around and use the new timeout value.  */
      if (err = (_hurd_itimer_thread_suspended
               ? __thread_resume : __thread_abort) (_hurd_itimer_thread))
       {
         kill_itimer_thread ();
         goto out;
       }
      _hurd_itimer_thread_suspended = 0;
    }

  __spin_unlock (&_hurd_itimer_lock);
  _hurd_critical_section_unlock (crit);

  if (old != NULL)
    {
      old->it_value = remaining;
      old->it_interval = old_interval;
    }
  return 0;

 out:
  __spin_unlock (&_hurd_itimer_lock);
  _hurd_critical_section_unlock (crit);
  return __hurd_fail (err);
}

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static void subtract_timeval ( struct timeval from,
const struct timeval subtract 
) [inline, static]

Definition at line 58 of file setitimer.c.

{
  from->tv_usec -= subtract->tv_usec;
  from->tv_sec -= subtract->tv_sec;
  while (from->tv_usec < 0)
    {
      --from->tv_sec;
      from->tv_usec += 1000000;
    }
}

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text_set_element ( _hurd_fork_child_hook  ,
fork_itimer   
)
static void timer_thread ( void  ) [static]

Definition at line 73 of file setitimer.c.

{
  while (1)
    {
      error_t err;
      /* The only message we ever expect to receive is the reply from the
         signal thread to a sig_post call we did.  We never examine the
        contents.  */
      struct
       {
         mach_msg_header_t header;
         error_t return_code;
       } msg;

      /* Wait for a message on a port that noone sends to.  The purpose is
        the receive timeout.  Notice interrupts so that if we are
        thread_abort'd, we will loop around and fetch new values from
        _hurd_itimerval.  */
      err = __mach_msg (&msg.header,
                     MACH_RCV_MSG|MACH_RCV_TIMEOUT|MACH_RCV_INTERRUPT,
                     0, 0, _hurd_itimer_port,
                     _hurd_itimerval.it_value.tv_sec * 1000 +
                     _hurd_itimerval.it_value.tv_usec / 1000,
                     MACH_PORT_NULL);
      switch (err)
       {
       case MACH_RCV_TIMED_OUT:
         /* We got the expected timeout.  Send a message to the signal
            thread to tell it to post a SIGALRM signal.  We use
            _hurd_itimer_port as the reply port just so we will block until
            the signal thread has frobnicated things to reload the itimer or
            has terminated this thread.  */
         __msg_sig_post_request (_hurd_msgport,
                              _hurd_itimer_port,
                              MACH_MSG_TYPE_MAKE_SEND_ONCE,
                              SIGALRM, 0, __mach_task_self ());
         break;

       case MACH_RCV_INTERRUPTED:
         /* We were thread_abort'd.  This is to tell us that
            _hurd_itimerval has changed and we need to reexamine it
            and start waiting with the new timeout value.  */
         break;

       case MACH_MSG_SUCCESS:
         /* We got the reply message from the sig_post_request above.
            Ignore it and reexamine the timer value.  */
         __mach_msg_destroy (&msg.header); /* Just in case.  */
         break;

       default:
         /* Unexpected lossage.  Oh well, keep trying.  */
         break;
       }
    }
}

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Variable Documentation

Definition at line 32 of file setitimer.c.

mach_port_t _hurd_itimer_port

Definition at line 34 of file setitimer.c.

Definition at line 35 of file setitimer.c.

Definition at line 37 of file setitimer.c.

Definition at line 38 of file setitimer.c.

Definition at line 36 of file setitimer.c.