posix: Implement self-contained POSIX barriers

POSIX barriers are now available in all configurations and no longer
depend on --enable-posix.

Update #2514.
Update #3114.

9 files changed, 156 insertions, 290 deletions

diff --git a/cpukit/posix/Makefile.am b/cpukit/posix/Makefile.am
index 1d9e209101..7980ca3cc5 100644
--- a/cpukit/posix/Makefile.am
+++ b/cpukit/posix/Makefile.am
@@ -16,6 +16,7 @@ include_rtems_posixdir = $(includedir)/rtems/posix
 include_rtems_posix_HEADERS = include/rtems/posix/sigset.h
 
 ## Some POSIX threads features are needed all the time
+include_rtems_posix_HEADERS += include/rtems/posix/barrierimpl.h
 include_rtems_posix_HEADERS += include/rtems/posix/key.h
 include_rtems_posix_HEADERS += include/rtems/posix/keyimpl.h
 include_rtems_posix_HEADERS += include/rtems/posix/config.h
@@ -49,8 +50,6 @@ include_rtems_posix_HEADERS += include/rtems/posix/shmimpl.h
 include_rtems_posix_HEADERS += include/rtems/posix/threadsup.h
 include_rtems_posix_HEADERS += include/rtems/posix/timer.h
 include_rtems_posix_HEADERS += include/rtems/posix/timerimpl.h
-include_rtems_posix_HEADERS += include/rtems/posix/barrier.h
-include_rtems_posix_HEADERS += include/rtems/posix/barrierimpl.h
 include_rtems_posix_HEADERS += include/rtems/posix/rwlock.h
 include_rtems_posix_HEADERS += include/rtems/posix/rwlockimpl.h
 
@@ -68,15 +67,15 @@ libposix_a_SOURCES += src/wait.c src/waitpid.c
 libposix_a_SOURCES += src/pthreadgetnamenp.c
 libposix_a_SOURCES += src/pthreadsetnamenp.c
 
-if HAS_PTHREADS
-libposix_a_SOURCES +=  src/pthreadatfork.c
-
 ## BARRIER_C_FILES
 libposix_a_SOURCES += src/barrierattrdestroy.c src/barrierattrgetpshared.c \
-    src/barrierattrinit.c src/barrierattrsetpshared.c src/pbarrier.c \
+    src/barrierattrinit.c src/barrierattrsetpshared.c \
     src/pbarrierdestroy.c src/pbarrierinit.c \
     src/pbarrierwait.c
 
+if HAS_PTHREADS
+libposix_a_SOURCES +=  src/pthreadatfork.c
+
 ## CANCEL_C_FILES
 libposix_a_SOURCES += src/cancel.c \
     src/cleanuppush.c src/setcancelstate.c \
diff --git a/cpukit/posix/include/rtems/posix/barrier.h b/cpukit/posix/include/rtems/posix/barrier.h
deleted file mode 100644
index e445586511..0000000000
--- a/cpukit/posix/include/rtems/posix/barrier.h
+++ /dev/null
@@ -1,64 +0,0 @@
-/**
- * @file
- * 
- * @brief Constants and Structures Associated with the POSIX Barrier Manager
- *
- * This include file contains all the constants and structures associated
- * with the POSIX Barrier Manager.
- *
- * Directives provided are:
- *
- *  - create a barrier
- *  - delete a barrier
- *  - wait for a barrier
- */
-
-/*
- *  COPYRIGHT (c) 1989-2011.
- *  On-Line Applications Research Corporation (OAR).
- *
- *  The license and distribution terms for this file may be
- *  found in the file LICENSE in this distribution or at
- *  http://www.rtems.org/license/LICENSE.
- */
-
-#ifndef _RTEMS_POSIX_BARRIER_H
-#define _RTEMS_POSIX_BARRIER_H
-
-#include <rtems/score/object.h>
-#include <rtems/score/corebarrier.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/**
- * @defgroup POSIXBarrier POSIX Barriers
- *
- * @ingroup POSIXAPI
- *
- * This encapsulates functionality which implements the RTEMS API
- * Barrier Manager.
- * 
- */
-/**@{**/
-
-/**
- * This type defines the control block used to manage each barrier.
- */
-
-typedef struct {
-  /** This is used to manage a barrier as an object. */
-  Objects_Control          Object;
-  /** This is used to implement the barrier. */
-  CORE_barrier_Control     Barrier;
-}   POSIX_Barrier_Control;
-
-#ifdef __cplusplus
-}
-#endif
-
-/** @} */
-
-#endif
-/*  end of include file */
diff --git a/cpukit/posix/include/rtems/posix/barrierimpl.h b/cpukit/posix/include/rtems/posix/barrierimpl.h
index fae66a6171..a1794b82fd 100644
--- a/cpukit/posix/include/rtems/posix/barrierimpl.h
+++ b/cpukit/posix/include/rtems/posix/barrierimpl.h
@@ -11,6 +11,8 @@
  *  COPYRIGHT (c) 1989-2011.
  *  On-Line Applications Research Corporation (OAR).
  *
+ *  Copyright (c) 2017 embedded brains GmbH
+ *
  *  The license and distribution terms for this file may be
  *  found in the file LICENSE in this distribution or at
  *  http://www.rtems.org/license/LICENSE.
@@ -19,63 +21,76 @@
 #ifndef _RTEMS_POSIX_BARRIERIMPL_H
 #define _RTEMS_POSIX_BARRIERIMPL_H
 
-#include <rtems/posix/barrier.h>
-#include <rtems/score/corebarrierimpl.h>
-#include <rtems/score/objectimpl.h>
-
 #include <errno.h>
 #include <pthread.h>
 
+#include <rtems/score/percpu.h>
+#include <rtems/score/threadqimpl.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/**
- *  The following defines the information control block used to manage
- *  this class of objects.
- */
+#define POSIX_BARRIER_MAGIC 0x1cf03773UL
 
-extern Objects_Information _POSIX_Barrier_Information;
+#define POSIX_BARRIER_TQ_OPERATIONS &_Thread_queue_Operations_FIFO
 
-/**
- * @brief Allocate a barrier control block.
- *
- * This function allocates a barrier control block from
- * the inactive chain of free barrier control blocks.
- */
-RTEMS_INLINE_ROUTINE POSIX_Barrier_Control *_POSIX_Barrier_Allocate( void )
+typedef struct {
+  unsigned long flags;
+  Thread_queue_Syslock_queue Queue;
+  unsigned int count;
+  unsigned int waiting_threads;
+} POSIX_Barrier_Control;
+
+static inline POSIX_Barrier_Control *_POSIX_Barrier_Get(
+  pthread_barrier_t *_barrier
+)
 {
-  return (POSIX_Barrier_Control *) 
-    _Objects_Allocate( &_POSIX_Barrier_Information );
+  return (POSIX_Barrier_Control *) _barrier;
 }
 
-/**
- * @brief Free a barrier control block.
- *
- * This routine frees a barrier control block to the
- * inactive chain of free barrier control blocks.
- */
-RTEMS_INLINE_ROUTINE void _POSIX_Barrier_Free (
-  POSIX_Barrier_Control *the_barrier
+static inline Thread_Control *_POSIX_Barrier_Queue_acquire(
+  POSIX_Barrier_Control *barrier,
+  Thread_queue_Context  *queue_context
 )
 {
-  _CORE_barrier_Destroy( &the_barrier->Barrier );
-  _Objects_Free( &_POSIX_Barrier_Information, &the_barrier->Object );
+  ISR_Level       level;
+  Thread_Control *executing;
+
+  _Thread_queue_Context_initialize( queue_context );
+  _Thread_queue_Context_ISR_disable( queue_context, level );
+  _Thread_queue_Context_set_ISR_level( queue_context, level );
+  executing = _Thread_Executing;
+  _Thread_queue_Queue_acquire_critical(
+    &barrier->Queue.Queue,
+    &executing->Potpourri_stats,
+    &queue_context->Lock_context.Lock_context
+  );
+
+  return executing;
 }
 
-RTEMS_INLINE_ROUTINE POSIX_Barrier_Control *_POSIX_Barrier_Get(
-  const pthread_barrier_t *barrier,
-  Thread_queue_Context    *queue_context
+static inline void _POSIX_Barrier_Queue_release(
+  POSIX_Barrier_Control *barrier,
+  Thread_queue_Context  *queue_context
 )
 {
-  _Thread_queue_Context_initialize( queue_context );
-  return (POSIX_Barrier_Control *) _Objects_Get(
-    (Objects_Id) *barrier,
-    &queue_context->Lock_context.Lock_context,
-    &_POSIX_Barrier_Information
+  _Thread_queue_Queue_release(
+    &barrier->Queue.Queue,
+    &queue_context->Lock_context.Lock_context
   );
 }
 
+#define POSIX_BARRIER_VALIDATE_OBJECT( bar ) \
+  do { \
+    if ( \
+      ( bar ) == NULL \
+        || ( (uintptr_t) ( bar ) ^ POSIX_BARRIER_MAGIC ) != ( bar )->_flags \
+    ) { \
+      return EINVAL; \
+    } \
+  } while ( 0 )
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/cpukit/posix/include/rtems/posix/config.h b/cpukit/posix/include/rtems/posix/config.h
index 6c74216dc2..dc1ef0c2f1 100644
--- a/cpukit/posix/include/rtems/posix/config.h
+++ b/cpukit/posix/include/rtems/posix/config.h
@@ -100,12 +100,6 @@ typedef struct {
 
   /**
    * This field contains the maximum number of POSIX API
-   * barriers which are configured for this application.
-   */
-  uint32_t                            maximum_barriers;
-
-  /**
-   * This field contains the maximum number of POSIX API
    * read/write locks which are configured for this application.
    */
   uint32_t                            maximum_rwlocks;
diff --git a/cpukit/posix/preinstall.am b/cpukit/posix/preinstall.am
index d67f9face8..903591ad65 100644
--- a/cpukit/posix/preinstall.am
+++ b/cpukit/posix/preinstall.am
@@ -27,6 +27,10 @@ $(PROJECT_INCLUDE)/rtems/posix/sigset.h: include/rtems/posix/sigset.h $(PROJECT_
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/sigset.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/sigset.h
 
+$(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h: include/rtems/posix/barrierimpl.h $(PROJECT_INCLUDE)/rtems/posix/$(dirstamp)
+	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h
+PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h
+
 $(PROJECT_INCLUDE)/rtems/posix/key.h: include/rtems/posix/key.h $(PROJECT_INCLUDE)/rtems/posix/$(dirstamp)
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/key.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/key.h
@@ -140,14 +144,6 @@ $(PROJECT_INCLUDE)/rtems/posix/timerimpl.h: include/rtems/posix/timerimpl.h $(PR
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/timerimpl.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/timerimpl.h
 
-$(PROJECT_INCLUDE)/rtems/posix/barrier.h: include/rtems/posix/barrier.h $(PROJECT_INCLUDE)/rtems/posix/$(dirstamp)
-	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/barrier.h
-PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/barrier.h
-
-$(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h: include/rtems/posix/barrierimpl.h $(PROJECT_INCLUDE)/rtems/posix/$(dirstamp)
-	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h
-PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/barrierimpl.h
-
 $(PROJECT_INCLUDE)/rtems/posix/rwlock.h: include/rtems/posix/rwlock.h $(PROJECT_INCLUDE)/rtems/posix/$(dirstamp)
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/posix/rwlock.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/posix/rwlock.h
diff --git a/cpukit/posix/src/pbarrier.c b/cpukit/posix/src/pbarrier.c
deleted file mode 100644
index 8216a080b1..0000000000
--- a/cpukit/posix/src/pbarrier.c
+++ /dev/null
@@ -1,51 +0,0 @@
-/**
- *  @file
- *
- *  This file initializes the POSIX Barrier Manager.
- */
-
-/*
- *  COPYRIGHT (c) 1989-2013.
- *  On-Line Applications Research Corporation (OAR).
- *
- *  The license and distribution terms for this file may be
- *  found in the file LICENSE in this distribution or at
- *  http://www.rtems.org/license/LICENSE.
- */
-
-#if HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#include <limits.h>
-
-#include <rtems/system.h>
-#include <rtems/config.h>
-#include <rtems/sysinit.h>
-#include <rtems/posix/barrierimpl.h>
-
-Objects_Information _POSIX_Barrier_Information;
-
-/**
- *  @brief _POSIX_Barrier_Manager_initialization
- */
-static void _POSIX_Barrier_Manager_initialization(void)
-{
-  _Objects_Initialize_information(
-    &_POSIX_Barrier_Information,    /* object information table */
-    OBJECTS_POSIX_API,              /* object API */
-    OBJECTS_POSIX_BARRIERS,         /* object class */
-    Configuration_POSIX_API.maximum_barriers,
-				    /* maximum objects of this class */
-    sizeof( POSIX_Barrier_Control ),/* size of this object's control block */
-    true,                           /* true if the name is a string */
-    _POSIX_PATH_MAX,                /* maximum length of each object's name */
-    NULL                            /* Proxy extraction support callout */
-  );
-}
-
-RTEMS_SYSINIT_ITEM(
-  _POSIX_Barrier_Manager_initialization,
-  RTEMS_SYSINIT_POSIX_BARRIER,
-  RTEMS_SYSINIT_ORDER_MIDDLE
-);
diff --git a/cpukit/posix/src/pbarrierdestroy.c b/cpukit/posix/src/pbarrierdestroy.c
index 8f85762211..83d06318b5 100644
--- a/cpukit/posix/src/pbarrierdestroy.c
+++ b/cpukit/posix/src/pbarrierdestroy.c
@@ -9,6 +9,8 @@
  *  COPYRIGHT (c) 1989-2007.
  *  On-Line Applications Research Corporation (OAR).
  *
+ *  Copyright (c) 2017 embedded brains GmbH
+ *
  *  The license and distribution terms for this file may be
  *  found in the file LICENSE in this distribution or at
  *  http://www.rtems.org/license/LICENSE.
@@ -20,47 +22,23 @@
 
 #include <rtems/posix/barrierimpl.h>
 
-/**
- *  This directive allows a thread to delete a barrier specified by
- *  the barrier id.  The barrier is freed back to the inactive
- *  barrier chain.
- *
- *  @param[in] barrier is the barrier id
- * 
- *  @return This method returns 0 if there was not an
- *  error. Otherwise, a status code is returned indicating the
- *  source of the error.
- */
-int pthread_barrier_destroy(
-  pthread_barrier_t *barrier
-)
+int pthread_barrier_destroy( pthread_barrier_t *_barrier )
 {
-  POSIX_Barrier_Control *the_barrier;
+  POSIX_Barrier_Control *barrier;
   Thread_queue_Context   queue_context;
 
-  if ( barrier == NULL ) {
-    return EINVAL;
-  }
-
-  _Objects_Allocator_lock();
-  the_barrier = _POSIX_Barrier_Get( barrier, &queue_context );
+  POSIX_BARRIER_VALIDATE_OBJECT( _barrier );
 
-  if ( the_barrier == NULL ) {
-    _Objects_Allocator_unlock();
-    return EINVAL;
-  }
+  barrier = _POSIX_Barrier_Get( _barrier );
 
-  _CORE_barrier_Acquire_critical( &the_barrier->Barrier, &queue_context );
+  _POSIX_Barrier_Queue_acquire( barrier, &queue_context );
 
-  if ( the_barrier->Barrier.number_of_waiting_threads != 0 ) {
-    _CORE_barrier_Release( &the_barrier->Barrier, &queue_context );
-    _Objects_Allocator_unlock();
+  if ( barrier->waiting_threads != 0 ) {
+    _POSIX_Barrier_Queue_release( barrier, &queue_context );
     return EBUSY;
   }
 
-  _Objects_Close( &_POSIX_Barrier_Information, &the_barrier->Object );
-  _CORE_barrier_Release( &the_barrier->Barrier, &queue_context );
-  _POSIX_Barrier_Free( the_barrier );
-  _Objects_Allocator_unlock();
+  barrier->flags = 0;
+  _POSIX_Barrier_Queue_release( barrier, &queue_context );
   return 0;
 }
diff --git a/cpukit/posix/src/pbarrierinit.c b/cpukit/posix/src/pbarrierinit.c
index c14cc0cb90..1fa22cb024 100644
--- a/cpukit/posix/src/pbarrierinit.c
+++ b/cpukit/posix/src/pbarrierinit.c
@@ -11,6 +11,8 @@
  *  COPYRIGHT (c) 1989-2006.
  *  On-Line Applications Research Corporation (OAR).
  *
+ *  Copyright (c) 2017 embedded brains GmbH
+ *
  *  The license and distribution terms for this file may be
  *  found in the file LICENSE in this distribution or at
  *  http://www.rtems.org/license/LICENSE.
@@ -20,91 +22,74 @@
 #include "config.h"
 #endif
 
-#include <pthread.h>
-#include <errno.h>
-
-#include <rtems/system.h>
 #include <rtems/posix/barrierimpl.h>
 #include <rtems/posix/posixapi.h>
 
-/*
- *  pthread_barrier_init
- *
- *  This directive creates a barrier.  A barrier id is returned.
- *
- *  Input parameters:
- *    barrier          - pointer to barrier id
- *    attr             - barrier attributes
- *    count            - number of threads before automatic release
- *
- *  Output parameters:
- *    barrier     - barrier id
- *    0           - if successful
- *    error code  - if unsuccessful
- */
+RTEMS_STATIC_ASSERT(
+  offsetof( POSIX_Barrier_Control, flags )
+    == offsetof( pthread_barrier_t, _flags ),
+  POSIX_BARRIER_CONTROL_FLAGS
+);
+
+RTEMS_STATIC_ASSERT(
+  offsetof( POSIX_Barrier_Control, count )
+    == offsetof( pthread_barrier_t, _count ),
+  POSIX_BARRIER_CONTROL_COUNT
+);
+
+RTEMS_STATIC_ASSERT(
+  offsetof( POSIX_Barrier_Control, waiting_threads )
+    == offsetof( pthread_barrier_t, _waiting_threads ),
+  POSIX_BARRIER_CONTROL_WAITING_THREADS
+);
+
+RTEMS_STATIC_ASSERT(
+  offsetof( POSIX_Barrier_Control, Queue )
+    == offsetof( pthread_barrier_t, _Queue ),
+  POSIX_BARRIER_CONTROL_QUEUE
+);
+
+RTEMS_STATIC_ASSERT(
+  sizeof( POSIX_Barrier_Control ) == sizeof( pthread_barrier_t ),
+  POSIX_BARRIER_CONTROL_SIZE
+);
 
 int pthread_barrier_init(
-  pthread_barrier_t           *barrier,
+  pthread_barrier_t           *_barrier,
   const pthread_barrierattr_t *attr,
   unsigned int                 count
 )
 {
-  POSIX_Barrier_Control         *the_barrier;
-  CORE_barrier_Attributes        the_attributes;
-  pthread_barrierattr_t          my_attr;
-  const pthread_barrierattr_t   *the_attr;
+  POSIX_Barrier_Control *barrier;
+
+  barrier = _POSIX_Barrier_Get( _barrier );
 
   /*
    *  Error check parameters
    */
-  if ( !barrier )
+  if ( barrier == NULL ) {
     return EINVAL;
-
-  if ( count == 0 )
-    return EINVAL;
-
-  /*
-   * If the user passed in NULL, use the default attributes
-   */
-  if ( attr ) {
-    the_attr = attr;
-  } else {
-    (void) pthread_barrierattr_init( &my_attr );
-    the_attr = &my_attr;
   }
 
-  /*
-   * Now start error checking the attributes that we are going to use
-   */
-  if ( !the_attr->is_initialized )
-    return EINVAL;
-
-  if ( !_POSIX_Is_valid_pshared( the_attr->process_shared ) ) {
+  if ( count == 0 ) {
     return EINVAL;
   }
 
-  /*
-   * Convert from POSIX attributes to Core Barrier attributes
-   */
-  the_attributes.discipline    = CORE_BARRIER_AUTOMATIC_RELEASE;
-  the_attributes.maximum_count = count;
-
-  the_barrier = _POSIX_Barrier_Allocate();
+  if ( attr != NULL ) {
+    /*
+     * Now start error checking the attributes that we are going to use
+     */
+    if ( !attr->is_initialized )
+      return EINVAL;
 
-  if ( !the_barrier ) {
-    _Objects_Allocator_unlock();
-    return EAGAIN;
+    if ( !_POSIX_Is_valid_pshared( attr->process_shared ) ) {
+      return EINVAL;
+    }
   }
 
-  _CORE_barrier_Initialize( &the_barrier->Barrier, &the_attributes );
-
-  _Objects_Open_u32(
-    &_POSIX_Barrier_Information,
-    &the_barrier->Object,
-    0
-  );
-
-  *barrier = the_barrier->Object.id;
-  _Objects_Allocator_unlock();
+  barrier->flags = (uintptr_t) barrier ^ POSIX_BARRIER_MAGIC;
+  barrier->count = count;
+  barrier->waiting_threads = 0;
+  _Thread_queue_Queue_initialize( &barrier->Queue.Queue, NULL );
   return 0;
 }
diff --git a/cpukit/posix/src/pbarrierwait.c b/cpukit/posix/src/pbarrierwait.c
index 117beac553..9719112256 100644
--- a/cpukit/posix/src/pbarrierwait.c
+++ b/cpukit/posix/src/pbarrierwait.c
@@ -9,6 +9,8 @@
  *  COPYRIGHT (c) 1989-2007.
  *  On-Line Applications Research Corporation (OAR).
  *
+ *  Copyright (c) 2017 embedded brains GmbH
+ *
  *  The license and distribution terms for this file may be
  *  found in the file LICENSE in this distribution or at
  *  http://www.rtems.org/license/LICENSE.
@@ -21,32 +23,44 @@
 #include <rtems/posix/barrierimpl.h>
 #include <rtems/posix/posixapi.h>
 
-THREAD_QUEUE_OBJECT_ASSERT( POSIX_Barrier_Control, Barrier.Wait_queue );
-
-int pthread_barrier_wait(
-  pthread_barrier_t *barrier
-)
+int pthread_barrier_wait( pthread_barrier_t *_barrier )
 {
-  POSIX_Barrier_Control *the_barrier;
+  POSIX_Barrier_Control *barrier;
   Thread_queue_Context   queue_context;
-  Status_Control         status;
+  Thread_Control        *executing;
+  unsigned int           waiting_threads;
 
-  if ( barrier == NULL ) {
-    return EINVAL;
-  }
+  POSIX_BARRIER_VALIDATE_OBJECT( _barrier );
 
-  the_barrier = _POSIX_Barrier_Get( barrier, &queue_context );
+  barrier = _POSIX_Barrier_Get( _barrier );
 
-  if ( the_barrier == NULL ) {
-    return EINVAL;
-  }
+  executing = _POSIX_Barrier_Queue_acquire( barrier, &queue_context );
+  waiting_threads = barrier->waiting_threads;
+  ++waiting_threads;
 
-  _Thread_queue_Context_set_no_timeout( &queue_context );
-  status = _CORE_barrier_Seize(
-    &the_barrier->Barrier,
-    _Thread_Executing,
-    true,
-    &queue_context
-  );
-  return _POSIX_Get_error( status );
+  if ( waiting_threads == barrier->count ) {
+    barrier->waiting_threads = 0;
+    _Thread_queue_Flush_critical(
+      &barrier->Queue.Queue,
+      POSIX_BARRIER_TQ_OPERATIONS,
+      _Thread_queue_Flush_default_filter,
+      &queue_context
+    );
+    return PTHREAD_BARRIER_SERIAL_THREAD;
+  } else {
+    barrier->waiting_threads = waiting_threads;
+    _Thread_queue_Context_set_thread_state(
+      &queue_context,
+      STATES_WAITING_FOR_BARRIER
+    );
+    _Thread_queue_Context_set_do_nothing_enqueue_callout( &queue_context );
+    _Thread_queue_Context_set_no_timeout( &queue_context );
+    _Thread_queue_Enqueue(
+      &barrier->Queue.Queue,
+      POSIX_BARRIER_TQ_OPERATIONS,
+      executing,
+      &queue_context
+    );
+    return 0;
+  }
 }