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glibc  2.9
Functions
pthread_mutex_setprioceiling.c File Reference
#include <stdbool.h>
#include <errno.h>
#include <pthreadP.h>

Go to the source code of this file.

Functions

int pthread_mutex_setprioceiling (pthread_mutex_t *mutex, int prioceiling, int *old_ceiling)

Function Documentation

int pthread_mutex_setprioceiling ( pthread_mutex_t mutex,
int  prioceiling,
int old_ceiling 
)

Definition at line 27 of file pthread_mutex_setprioceiling.c.

{
  /* The low bits of __kind aren't ever changed after pthread_mutex_init,
     so we don't need a lock yet.  */
  if ((mutex->__data.__kind & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0)
    return EINVAL;

  if (__sched_fifo_min_prio == -1)
    __init_sched_fifo_prio ();

  if (__builtin_expect (prioceiling < __sched_fifo_min_prio, 0)
      || __builtin_expect (prioceiling > __sched_fifo_max_prio, 0)
      || __builtin_expect ((prioceiling
                         & (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK
                            >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT))
                        != prioceiling, 0))
    return EINVAL;

  /* Check whether we already hold the mutex.  */
  bool locked = false;
  int kind = PTHREAD_MUTEX_TYPE (mutex);
  if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid))
    {
      if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP)
       return EDEADLK;

      if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP)
       locked = true;
    }

  int oldval = mutex->__data.__lock;
  if (! locked)
    do
      {
       /* Need to lock the mutex, but without obeying the priority
          protect protocol.  */
       int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK);

       oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
                                                ceilval | 1, ceilval);
       if (oldval == ceilval)
         break;

       do
         {
           oldval
             = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
                                               ceilval | 2,
                                               ceilval | 1);

           if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
             break;

           if (oldval != ceilval)
             lll_futex_wait (&mutex->__data.__lock, ceilval | 2,
                           PTHREAD_MUTEX_PSHARED (mutex));
         }
       while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
                                              ceilval | 2, ceilval)
              != ceilval);

       if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
         continue;
      }
    while (0);

  int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
              >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
  if (locked)
    {
      int ret = __pthread_tpp_change_priority (oldprio, prioceiling);
      if (ret)
       return ret;
    }

  if (old_ceiling != NULL)
    *old_ceiling = oldprio;

  int newlock = 0;
  if (locked)
    newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK);
  mutex->__data.__lock = newlock
                      | (prioceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT);
  atomic_full_barrier ();

  lll_futex_wake (&mutex->__data.__lock, INT_MAX,
                PTHREAD_MUTEX_PSHARED (mutex));

  return 0;
}

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