1 files changed, 106 insertions, 0 deletions
diff --git a/cpukit/score/src/corerwlockrelease.c b/cpukit/score/src/corerwlockrelease.c
new file mode 100644
index 0000000000..379fdebdec
--- /dev/null
+++ b/cpukit/score/src/corerwlockrelease.c
@@ -0,0 +1,106 @@
+/*
+ *  SuperCore RWLock Handler -- Release a RWLock
+ *
+ *  COPYRIGHT (c) 1989-2006.
+ *  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.com/license/LICENSE.
+ *
+ *  $Id$
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/system.h>
+#include <rtems/score/corerwlock.h>
+#include <rtems/score/states.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/watchdog.h>
+
+/*PAGE
+ *
+ *  _CORE_RWLock_Release
+ *
+ *  This function releases the rwlock.
+ *
+ *  Input parameters:
+ *    the_rwlock    - the rwlock control block to initialize
+ *
+ *  Output parameters:  NONE
+ */
+
+CORE_RWLock_Status _CORE_RWLock_Release(
+  CORE_RWLock_Control  *the_rwlock
+)
+{
+  ISR_Level       level;
+  Thread_Control *executing = _Thread_Executing;
+  Thread_Control *next;
+
+  /*
+   *  If unlocked, then OK to read.
+   *  Otherwise, we have to block.
+   *  If locked for reading and no waiters, then OK to read.
+   *  If any thread is waiting, then we wait.
+   */
+
+  _ISR_Disable( level );
+    if ( the_rwlock->current_state == CORE_RWLOCK_UNLOCKED){
+      _ISR_Enable( level );
+      executing->Wait.return_code = CORE_RWLOCK_UNAVAILABLE;
+      return CORE_RWLOCK_SUCCESSFUL;
+    }
+    if ( the_rwlock->current_state == CORE_RWLOCK_LOCKED_FOR_READING ) {
+	the_rwlock->number_of_readers -= 1;
+	if ( the_rwlock->number_of_readers != 0 ) {
+          /* must be unlocked again */
+	  _ISR_Enable( level );
+          return CORE_RWLOCK_SUCCESSFUL;
+        }
+    }
+
+    /* CORE_RWLOCK_LOCKED_FOR_WRITING or READING with readers */
+    executing->Wait.return_code = CORE_RWLOCK_SUCCESSFUL;
+
+    /*
+     * Implicitly transition to "unlocked" and find another thread interested
+     * in obtaining this rwlock.
+     */
+    the_rwlock->current_state = CORE_RWLOCK_UNLOCKED;
+  _ISR_Enable( level );
+
+  next = _Thread_queue_Dequeue( &the_rwlock->Wait_queue );
+
+  if ( next ) {
+    if ( next->Wait.option == CORE_RWLOCK_THREAD_WAITING_FOR_WRITE ) {
+      the_rwlock->current_state = CORE_RWLOCK_LOCKED_FOR_WRITING;
+      return CORE_RWLOCK_SUCCESSFUL;
+    }
+
+    /*
+     * Must be CORE_RWLOCK_THREAD_WAITING_FOR_READING
+     */
+    the_rwlock->number_of_readers += 1;
+    the_rwlock->current_state = CORE_RWLOCK_LOCKED_FOR_READING;
+
+    /*
+     * Now see if more readers can be let go.
+     */
+    while ( 1 ) {
+      next = _Thread_queue_First( &the_rwlock->Wait_queue );
+      if ( !next ||
+           next->Wait.option == CORE_RWLOCK_THREAD_WAITING_FOR_WRITE )
+        return CORE_RWLOCK_SUCCESSFUL;
+      the_rwlock->number_of_readers += 1;
+      _Thread_queue_Extract( &the_rwlock->Wait_queue, next );
+    }
+  }
+
+  /* indentation is to match _ISR_Disable at top */
+
+  return CORE_RWLOCK_SUCCESSFUL;
+}