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glibc  2.9
Classes | Functions
pthread_cond_wait.c File Reference
#include <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>
#include <shlib-compat.h>

Go to the source code of this file.

Classes

struct  _condvar_cleanup_buffer

Functions

void __attribute__ ((visibility("hidden")))
int __pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
 versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait, GLIBC_2_3_2)

Class Documentation

struct _condvar_cleanup_buffer

Definition at line 35 of file pthread_cond_timedwait.c.

Collaboration diagram for _condvar_cleanup_buffer:
Class Members
unsigned int bc_seq
pthread_cond_t * cond
pthread_mutex_t * mutex
int oldtype

Function Documentation

void __attribute__ ( (visibility("hidden"))  )

Definition at line 40 of file pthread_cond_wait.c.

{
  struct _condvar_cleanup_buffer *cbuffer =
    (struct _condvar_cleanup_buffer *) arg;
  unsigned int destroying;
  int pshared = (cbuffer->cond->__data.__mutex == (void *) ~0l)
              ? LLL_SHARED : LLL_PRIVATE;

  /* We are going to modify shared data.  */
  lll_lock (cbuffer->cond->__data.__lock, pshared);

  if (cbuffer->bc_seq == cbuffer->cond->__data.__broadcast_seq)
    {
      /* This thread is not waiting anymore.  Adjust the sequence counters
        appropriately.  We do not increment WAKEUP_SEQ if this would
        bump it over the value of TOTAL_SEQ.  This can happen if a thread
        was woken and then canceled.  */
      if (cbuffer->cond->__data.__wakeup_seq
         < cbuffer->cond->__data.__total_seq)
       {
         ++cbuffer->cond->__data.__wakeup_seq;
         ++cbuffer->cond->__data.__futex;
       }
      ++cbuffer->cond->__data.__woken_seq;
    }

  cbuffer->cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;

  /* If pthread_cond_destroy was called on this variable already,
     notify the pthread_cond_destroy caller all waiters have left
     and it can be successfully destroyed.  */
  destroying = 0;
  if (cbuffer->cond->__data.__total_seq == -1ULL
      && cbuffer->cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
    {
      lll_futex_wake (&cbuffer->cond->__data.__nwaiters, 1, pshared);
      destroying = 1;
    }

  /* We are done.  */
  lll_unlock (cbuffer->cond->__data.__lock, pshared);

  /* Wake everybody to make sure no condvar signal gets lost.  */
  if (! destroying)
    lll_futex_wake (&cbuffer->cond->__data.__futex, INT_MAX, pshared);

  /* Get the mutex before returning unless asynchronous cancellation
     is in effect.  */
  __pthread_mutex_cond_lock (cbuffer->mutex);
}

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Definition at line 94 of file pthread_cond_wait.c.

{
  struct _pthread_cleanup_buffer buffer;
  struct _condvar_cleanup_buffer cbuffer;
  int err;
  int pshared = (cond->__data.__mutex == (void *) ~0l)
              ? LLL_SHARED : LLL_PRIVATE;

  /* Make sure we are along.  */
  lll_lock (cond->__data.__lock, pshared);

  /* Now we can release the mutex.  */
  err = __pthread_mutex_unlock_usercnt (mutex, 0);
  if (__builtin_expect (err, 0))
    {
      lll_unlock (cond->__data.__lock, pshared);
      return err;
    }

  /* We have one new user of the condvar.  */
  ++cond->__data.__total_seq;
  ++cond->__data.__futex;
  cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;

  /* Remember the mutex we are using here.  If there is already a
     different address store this is a bad user bug.  Do not store
     anything for pshared condvars.  */
  if (cond->__data.__mutex != (void *) ~0l)
    cond->__data.__mutex = mutex;

  /* Prepare structure passed to cancellation handler.  */
  cbuffer.cond = cond;
  cbuffer.mutex = mutex;

  /* Before we block we enable cancellation.  Therefore we have to
     install a cancellation handler.  */
  __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);

  /* The current values of the wakeup counter.  The "woken" counter
     must exceed this value.  */
  unsigned long long int val;
  unsigned long long int seq;
  val = seq = cond->__data.__wakeup_seq;
  /* Remember the broadcast counter.  */
  cbuffer.bc_seq = cond->__data.__broadcast_seq;

  do
    {
      unsigned int futex_val = cond->__data.__futex;

      /* Prepare to wait.  Release the condvar futex.  */
      lll_unlock (cond->__data.__lock, pshared);

      /* Enable asynchronous cancellation.  Required by the standard.  */
      cbuffer.oldtype = __pthread_enable_asynccancel ();

      /* Wait until woken by signal or broadcast.  */
      lll_futex_wait (&cond->__data.__futex, futex_val, pshared);

      /* Disable asynchronous cancellation.  */
      __pthread_disable_asynccancel (cbuffer.oldtype);

      /* We are going to look at shared data again, so get the lock.  */
      lll_lock (cond->__data.__lock, pshared);

      /* If a broadcast happened, we are done.  */
      if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
       goto bc_out;

      /* Check whether we are eligible for wakeup.  */
      val = cond->__data.__wakeup_seq;
    }
  while (val == seq || cond->__data.__woken_seq == val);

  /* Another thread woken up.  */
  ++cond->__data.__woken_seq;

 bc_out:

  cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;

  /* If pthread_cond_destroy was called on this varaible already,
     notify the pthread_cond_destroy caller all waiters have left
     and it can be successfully destroyed.  */
  if (cond->__data.__total_seq == -1ULL
      && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
    lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);

  /* We are done with the condvar.  */
  lll_unlock (cond->__data.__lock, pshared);

  /* The cancellation handling is back to normal, remove the handler.  */
  __pthread_cleanup_pop (&buffer, 0);

  /* Get the mutex before returning.  */
  return __pthread_mutex_cond_lock (mutex);
}

Here is the call graph for this function:

versioned_symbol ( libpthread  ,
__pthread_cond_wait  ,
pthread_cond_wait  ,
GLIBC_2_3_2   
)