NuttX RTOS

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@3 7fd9a85b-ad96-42d3-883c-3090e2eb8679

1 files changed, 177 insertions, 0 deletions

diff --git a/nuttx/mm/mm_sem.c b/nuttx/mm/mm_sem.c
new file mode 100644
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+/************************************************************
+ * mm_sem.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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 Gregory Nutt 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 "mm_environment.h"
+#include <unistd.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <assert.h>
+#include "mm_internal.h"
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/* Define the following to enable semaphore state monitoring */
+//#define MONITOR_MM_SEMAPHORE 1
+
+#ifdef MONITOR_MM_SEMAPHORE
+#  ifdef CONFIG_DEBUG
+#    include <debug.h>
+#    define msemdbg dbg
+#  else
+#    define msemdbg printf
+#  endif
+#else
+# define msemdbg(x...)
+#endif
+
+/************************************************************
+ * Private Data
+ ************************************************************/
+
+/* Mutually exclusive access to this data set is enforced with
+ * the following (un-named) semaphore. */
+
+static  sem_t g_mm_semaphore;
+static  pid_t g_holder;
+static  int   g_counts_held;
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * mm_seminitialize
+ ************************************************************/
+
+void mm_seminitialize(void)
+{
+  /* Initialize the MM semaphore to one (to support one-at-
+   * a-time access to private data sets.
+   */
+
+  (void)sem_init(&g_mm_semaphore, 0, 1);
+
+  g_holder      = -1;
+  g_counts_held = 0;
+}
+
+/************************************************************
+ * mm_takesemaphore
+ ************************************************************/
+
+void mm_takesemaphore(void)
+{
+  pid_t my_pid = getpid();
+
+  /* Do I already have the semaphore? */
+
+  if (g_holder == my_pid)
+    {
+      /* Yes, just increment the number of references that I have */
+
+      g_counts_held++;
+    }
+  else
+    {
+      /* Take the semaphore (perhaps waiting) */
+
+      msemdbg("%s: PID=%d taking\n", __FUNCTION__, my_pid);
+      while (sem_wait(&g_mm_semaphore) != 0)
+       {
+         /* The only case that an error should occur here is if
+          * the wait was awakened by a signal.
+          */
+
+         ASSERT(mm_errno == EINTR);
+       }
+
+      /* We have it.  Claim the stak and return */
+
+      g_holder      = my_pid;
+      g_counts_held = 1;
+    }
+
+  msemdbg("%s: Holder=%d count=%d\n",
+          __FUNCTION__, g_holder, g_counts_held);
+}
+
+/************************************************************
+ * mm_givesemaphore
+ ************************************************************/
+
+void mm_givesemaphore(void)
+{
+  pid_t my_pid = getpid();
+
+  /* I better be holding at least one reference to the semaphore */
+
+  ASSERT(g_holder == my_pid);
+
+  /* Do I hold multiple references to the semphore */
+
+  if (g_counts_held > 1)
+    {
+      /* Yes, just release one count and return */
+
+      g_counts_held--;
+      msemdbg("%s: Holder=%d count=%d\n",
+              __FUNCTION__, g_holder, g_counts_held);
+    }
+  else
+    {
+      /* Nope, this is the last reference I have */
+
+      msemdbg("%s: PID=%d giving\n", __FUNCTION__, my_pid);
+      g_holder = -1;
+      g_counts_held = 0;
+      ASSERT(sem_post(&g_mm_semaphore) == 0);
+    }
+}
+
+#ifdef MM_TEST
+int mm_getsemaphore(void)
+{
+  int sval;
+  sem_getvalue(&g_mm_semaphore, &sval);
+  return sval;
+}
+#endif
+