1 files changed, 137 insertions, 0 deletions
diff --git a/nuttx/sched/pthread_condsignal.c b/nuttx/sched/pthread_condsignal.c
new file mode 100644
index 000000000..48ff4cf20
--- /dev/null
+++ b/nuttx/sched/pthread_condsignal.c
@@ -0,0 +1,137 @@
+/****************************************************************************
+ * sched/pthread_condsignal.c
+ *
+ *   Copyright (C) 2007-2009, 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <pthread.h>
+#include <errno.h>
+#include <debug.h>
+
+#include "pthread_internal.h"
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pthread_cond_signal
+ *
+ * Description:
+ *    A thread can signal on a condition variable.
+ *
+ * Parameters:
+ *   None
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int pthread_cond_signal(FAR pthread_cond_t *cond)
+{
+  int ret = OK;
+  int sval;
+
+  sdbg("cond=0x%p\n", cond);
+
+  if (!cond)
+    {
+      ret = EINVAL;
+    }
+  else
+    {
+      /* Get the current value of the semaphore */
+
+      if (sem_getvalue((sem_t*)&cond->sem, &sval) != OK)
+        {
+          ret = EINVAL;
+        }
+
+      /* If the value is less than zero (meaning that one or more
+       * thread is waiting), then post the condition semaphore.
+       * Only the highest priority waiting thread will get to execute
+       */
+
+      else
+        {
+          /* One of my objectives in this design was to make pthread_cond_signal
+           * usable from interrupt handlers.  However, from interrupt handlers,
+           * you cannot take the associated mutex before signaling the condition.
+           * As a result, I think that there could be a race condition with
+           * the following logic which assumes that the if sval < 0 then the 
+           * thread is waiting.  Without the mutex, there is no atomic, protected
+           * operation that will guarantee this to be so.
+           */
+
+          sdbg("sval=%d\n", sval);
+          if (sval < 0)
+            {
+              sdbg("Signalling...\n");
+              ret = pthread_givesemaphore((sem_t*)&cond->sem);
+            }
+        }
+    }
+
+  sdbg("Returning %d\n", ret);
+  return ret;
+}
+
+