Resync new repository with old repo r5166

git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5153 42af7a65-404d-4744-a932-0658087f49c3

nuttx/sched/pthread_mutexlock.c

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+/****************************************************************************
+ * sched/pthread_mutexlock.c
+ *
+ *   Copyright (C) 2007-2009 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 <unistd.h>
+#include <pthread.h>
+#include <sched.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_mutex_lock
+ *
+ * Description:
+ *   The mutex object referenced by mutex is locked by calling
+ *   pthread_mutex_lock(). If the mutex is already locked, the calling thread
+ *   blocks until the mutex becomes available. This operation returns with the
+ *   mutex object referenced by mutex in the locked state with the calling
+ *   thread as its owner.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not
+ *   provided. Attempting to relock the mutex causes deadlock. If a thread
+ *   attempts to unlock a mutex that it has not locked or a mutex which is
+ *   unlocked, undefined behavior results.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is
+ *   provided. If a thread attempts to relock a mutex that it has already
+ *   locked, an error will be returned. If a thread attempts to unlock a
+ *   mutex that it has not locked or a mutex which is unlocked, an error will
+ *   be returned.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains
+ *   the concept of a lock count. When a thread successfully acquires a mutex
+ *   for the first time, the lock count is set to one. Every time a thread
+ *   relocks this mutex, the lock count is incremented by one. Each time the
+ *   thread unlocks the mutex, the lock count is decremented by one. When the
+ *   lock count reaches zero, the mutex becomes available for other threads to
+ *   acquire. If a thread attempts to unlock a mutex that it has not locked or
+ *   a mutex which is unlocked, an error will be returned.
+ *
+ *   If a signal is delivered to a thread waiting for a mutex, upon return
+ *   from the signal handler the thread resumes waiting for the mutex as if
+ *   it was not interrupted.
+ *
+ * Parameters:
+ *   mutex - A reference to the mutex to be locked.
+ *
+ * Return Value:
+ *   0 on success or an errno value on failure.  Note that the errno EINTR
+ *   is never returned by pthread_mutex_lock().
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
+{
+  int mypid = (int)getpid();
+  int ret = OK;
+
+  sdbg("mutex=0x%p\n", mutex);
+
+  if (!mutex)
+    {
+      ret = EINVAL;
+    }
+  else
+    {
+      /* Make sure the semaphore is stable while we make the following
+       * checks.  This all needs to be one atomic action.
+       */
+
+      sched_lock();
+
+      /* Does this task already hold the semaphore? */
+
+      if (mutex->pid == mypid)
+        {
+          /* Yes.. Is this a recursive mutex? */
+
+#ifdef CONFIG_MUTEX_TYPES
+          if (mutex->type == PTHREAD_MUTEX_RECURSIVE)
+            {
+              /* Yes... just increment the number of locks held and return success */
+          
+              mutex->nlocks++;
+            }
+          else
+#endif
+            {
+              /* No, then we would deadlock... return an error (default behavior
+               * is like PTHREAD_MUTEX_ERRORCHECK)
+               */
+
+              sdbg("Returning EDEADLK\n");
+              ret = EDEADLK;
+            }
+        }
+      else
+        {
+          /* Take the semaphore */
+
+          ret = pthread_takesemaphore((sem_t*)&mutex->sem);
+
+          /* If we succussfully obtained the semaphore, then indicate
+           * that we own it.
+           */
+
+          if (!ret)
+            {
+              mutex->pid    = mypid;
+#ifdef CONFIG_MUTEX_TYPES
+              mutex->nlocks = 1;
+#endif
+            }
+        }
+
+      sched_unlock();
+    }
+
+  sdbg("Returning %d\n", ret);
+  return ret;
+}
+