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semaphoreP.h File Reference
#include <semaphore.h>
#include "pthreadP.h"
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Classes

struct  mountpoint_info
struct  inuse_sem

Functions

void __where_is_shmfs (void) attribute_hidden
int __sem_search (const void *a, const void *b) attribute_hidden
int __new_sem_init (sem_t *sem, int pshared, unsigned int value)
int __old_sem_init (sem_t *sem, int pshared, unsigned int value)
int __new_sem_destroy (sem_t *sem)
int __new_sem_post (sem_t *sem)
int __new_sem_wait (sem_t *sem)
int __old_sem_wait (sem_t *sem)
int __new_sem_trywait (sem_t *sem)
int __new_sem_getvalue (sem_t *sem, int *sval)

Variables

pthread_once_t __namedsem_once attribute_hidden

Class Documentation

struct mountpoint_info

Definition at line 25 of file semaphoreP.h.

Class Members
char * dir
size_t dirlen
struct inuse_sem

Definition at line 32 of file semaphoreP.h.

Collaboration diagram for inuse_sem:
Class Members
dev_t dev
ino_t ino
char name
int refcnt
sem_t * sem

Function Documentation

Definition at line 184 of file semaphore.c.

{
  if (sem->__sem_waiting != NULL) {
    __set_errno (EBUSY);
    return -1;
  }
  return 0;
}
int __new_sem_getvalue ( sem_t sem,
int sval 
)

Definition at line 178 of file semaphore.c.

{
  *sval = sem->__sem_value;
  return 0;
}
int __new_sem_init ( sem_t sem,
int  pshared,
unsigned int  value 
)

Definition at line 27 of file semaphore.c.

{
  if (value > SEM_VALUE_MAX) {
    errno = EINVAL;
    return -1;
  }
  if (pshared) {
    errno = ENOSYS;
    return -1;
  }
  __pthread_init_lock(&sem->__sem_lock);
  sem->__sem_value = value;
  sem->__sem_waiting = NULL;
  return 0;
}

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int __new_sem_post ( sem_t sem)

Definition at line 137 of file semaphore.c.

{
  pthread_descr self = thread_self();
  pthread_descr th;
  struct pthread_request request;

  if (THREAD_GETMEM(self, p_in_sighandler) == NULL) {
    __pthread_lock(&sem->__sem_lock, self);
    if (sem->__sem_waiting == NULL) {
      if (sem->__sem_value >= SEM_VALUE_MAX) {
        /* Overflow */
        errno = ERANGE;
        __pthread_unlock(&sem->__sem_lock);
        return -1;
      }
      sem->__sem_value++;
      __pthread_unlock(&sem->__sem_lock);
    } else {
      th = dequeue(&sem->__sem_waiting);
      __pthread_unlock(&sem->__sem_lock);
      th->p_sem_avail = 1;
      WRITE_MEMORY_BARRIER();
      restart(th);
    }
  } else {
    /* If we're in signal handler, delegate post operation to
       the thread manager. */
    if (__pthread_manager_request < 0) {
      if (__pthread_initialize_manager() < 0) {
        errno = EAGAIN;
        return -1;
      }
    }
    request.req_kind = REQ_POST;
    request.req_args.post = sem;
    TEMP_FAILURE_RETRY(write_not_cancel(__pthread_manager_request,
                                   (char *) &request, sizeof(request)));
  }
  return 0;
}

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Definition at line 121 of file semaphore.c.

{
  int retval;

  __pthread_lock(&sem->__sem_lock, NULL);
  if (sem->__sem_value == 0) {
    errno = EAGAIN;
    retval = -1;
  } else {
    sem->__sem_value--;
    retval = 0;
  }
  __pthread_unlock(&sem->__sem_lock);
  return retval;
}

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int __new_sem_wait ( sem_t sem)

Definition at line 59 of file semaphore.c.

{
  volatile pthread_descr self = thread_self();
  pthread_extricate_if extr;
  int already_canceled = 0;
  int spurious_wakeup_count;

  /* Set up extrication interface */
  extr.pu_object = sem;
  extr.pu_extricate_func = new_sem_extricate_func;

  __pthread_lock(&sem->__sem_lock, self);
  if (sem->__sem_value > 0) {
    sem->__sem_value--;
    __pthread_unlock(&sem->__sem_lock);
    return 0;
  }
  /* Register extrication interface */
  THREAD_SETMEM(self, p_sem_avail, 0);
  __pthread_set_own_extricate_if(self, &extr);
  /* Enqueue only if not already cancelled. */
  if (!(THREAD_GETMEM(self, p_canceled)
      && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
    enqueue(&sem->__sem_waiting, self);
  else
    already_canceled = 1;
  __pthread_unlock(&sem->__sem_lock);

  if (already_canceled) {
    __pthread_set_own_extricate_if(self, 0);
    __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
  }

  /* Wait for sem_post or cancellation, or fall through if already canceled */
  spurious_wakeup_count = 0;
  while (1)
    {
      suspend(self);
      if (THREAD_GETMEM(self, p_sem_avail) == 0
         && (THREAD_GETMEM(self, p_woken_by_cancel) == 0
             || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
       {
         /* Count resumes that don't belong to us. */
         spurious_wakeup_count++;
         continue;
       }
      break;
    }
  __pthread_set_own_extricate_if(self, 0);

  /* Terminate only if the wakeup came from cancellation. */
  /* Otherwise ignore cancellation because we got the semaphore. */

  if (THREAD_GETMEM(self, p_woken_by_cancel)
      && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
    THREAD_SETMEM(self, p_woken_by_cancel, 0);
    __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
  }
  /* We got the semaphore */
  return 0;
}

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int __old_sem_init ( sem_t sem,
int  pshared,
unsigned int  value 
)
int __old_sem_wait ( sem_t sem)
int __sem_search ( const void *  a,
const void *  b 
)

Definition at line 129 of file sem_open.c.

{
  const struct inuse_sem *as = (const struct inuse_sem *) a;
  const struct inuse_sem *bs = (const struct inuse_sem *) b;

  if (as->ino != bs->ino)
    /* Cannot return the difference the type is larger than int.  */
    return as->ino < bs->ino ? -1 : (as->ino == bs->ino ? 0 : 1);

  if (as->dev != bs->dev)
    /* Cannot return the difference the type is larger than int.  */
    return as->dev < bs->dev ? -1 : (as->dev == bs->dev ? 0 : 1);

  return strcmp (as->name, bs->name);
}

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void __where_is_shmfs ( void  )

Definition at line 55 of file sem_open.c.

{
  char buf[512];
  struct statfs f;
  struct mntent resmem;
  struct mntent *mp;
  FILE *fp;

  /* The canonical place is /dev/shm.  This is at least what the
     documentation tells everybody to do.  */
  if (__statfs (defaultmount, &f) == 0 && f.f_type == SHMFS_SUPER_MAGIC)
    {
      /* It is in the normal place.  */
      mountpoint.dir = (char *) defaultdir;
      mountpoint.dirlen = sizeof (defaultdir) - 1;

      return;
    }

  /* OK, do it the hard way.  Look through the /proc/mounts file and if
     this does not exist through /etc/fstab to find the mount point.  */
  fp = __setmntent ("/proc/mounts", "r");
  if (__builtin_expect (fp == NULL, 0))
    {
      fp = __setmntent (_PATH_MNTTAB, "r");
      if (__builtin_expect (fp == NULL, 0))
       /* There is nothing we can do.  Blind guesses are not helpful.  */
       return;
    }

  /* Now read the entries.  */
  while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
    /* The original name is "shm" but this got changed in early Linux
       2.4.x to "tmpfs".  */
    if (strcmp (mp->mnt_type, "tmpfs") == 0
       || strcmp (mp->mnt_type, "shm") == 0)
      {
       /* Found it.  There might be more than one place where the
           filesystem is mounted but one is enough for us.  */
       size_t namelen;

       /* First make sure this really is the correct entry.  At least
          some versions of the kernel give wrong information because
          of the implicit mount of the shmfs for SysV IPC.  */
       if (__statfs (mp->mnt_dir, &f) != 0 || f.f_type != SHMFS_SUPER_MAGIC)
         continue;

       namelen = strlen (mp->mnt_dir);

       if (namelen == 0)
         /* Hum, maybe some crippled entry.  Keep on searching.  */
         continue;

       mountpoint.dir = (char *) malloc (namelen + 4 + 2);
       if (mountpoint.dir != NULL)
         {
           char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
           if (cp[-1] != '/')
             *cp++ = '/';
           cp = stpcpy (cp, "sem.");
           mountpoint.dirlen = cp - mountpoint.dir;
         }

       break;
      }

  /* Close the stream.  */
  __endmntent (fp);
}

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Variable Documentation

int __sem_mappings_lock attribute_hidden

Definition at line 48 of file semaphoreP.h.