Add sem_timedwait()

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3798 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 287 insertions, 0 deletions

diff --git a/nuttx/sched/sem_timedwait.c b/nuttx/sched/sem_timedwait.c
new file mode 100644
index 000000000..c02bc48db
--- /dev/null
+++ b/nuttx/sched/sem_timedwait.c
@@ -0,0 +1,287 @@
+/****************************************************************************
+ * sched/sem_timedwait.c
+ *
+ *   Copyright (C) 2010 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 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 <stdint.h>
+#include <unistd.h>
+#include <semaphore.h>
+#include <time.h>
+#include <errno.h>
+#include <wdog.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+
+#include "os_internal.h"
+#include "clock_internal.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  sem_timeout
+ *
+ * Description:
+ *   This function is called if the timeout elapses before the message queue
+ *   becomes non-empty.
+ *
+ * Parameters:
+ *   argc  - the number of arguments (should be 1)
+ *   pid   - the task ID of the task to wakeup
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+static void sem_timeout(int argc, uint32_t pid)
+{
+  FAR _TCB *wtcb;
+  irqstate_t flags;
+
+  /* Disable interrupts to avoid race conditions */
+
+  flags = irqsave();
+
+  /* Get the TCB associated with this pid.  It is possible that
+   * task may no longer be active when this watchdog goes off.
+   */
+
+  wtcb = sched_gettcb((pid_t)pid);
+
+  /* It is also possible that an interrupt/context switch beat us to the
+   * punch and already changed the task's state.
+   */
+
+  if (wtcb && wtcb->task_state == TSTATE_WAIT_SEM)
+    {
+      /* Mark the errno value for the thread. */
+
+      wtcb->pterrno = ETIMEDOUT;
+
+      /* Restart the task. */
+
+      up_unblock_task(wtcb);
+    }
+
+  /* Interrupts may now be enabled. */
+
+  irqrestore(flags);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  sem_timedwait
+ *
+ * Description:
+ *   This function will lock the semaphore referenced by sem as in the
+ *   sem_wait() function. However, if the semaphore cannot be locked without
+ *   waiting for another process or thread to unlock the semaphore by
+ *   performing a sem_post() function, this wait will be terminated when the
+ *   specified timeout expires.
+ *
+ *   The timeout will expire when the absolute time specified by abstime
+ *   passes, as measured by the clock on which timeouts are based (that is,
+ *   when the value of that clock equals or exceeds abstime), or if the
+ *   absolute time specified by abstime has already been passed at the
+ *   time of the call.
+ *
+ * Parameters:
+ *   sem - Semaphore object
+ *   abstime - The absolute time to wait until a timeout is declared.
+ *
+ * Return Value:
+ *   One success, the length of the selected message in bytes.is
+ *   returned.  On failure, -1 (ERROR) is returned and the errno
+ *   is set appropriately:
+ *
+ *   EINVAL    The sem argument does not refer to a valid semaphore.  Or the
+ *             thread would have blocked, and the abstime parameter specified
+ *             a nanoseconds field value less than zero or greater than or
+ *             equal to 1000 million.
+ *   ETIMEDOUT The semaphore could not be locked before the specified timeout
+ *             expired.
+ *   EDEADLK   A deadlock condition was detected.
+ *   EINTR     A signal interrupted this function.
+ *
+ ****************************************************************************/
+
+int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
+{
+  WDOG_ID    wdog;
+  irqstate_t flags;
+  int        ticks;
+  int        err;
+  int        ret = ERROR;
+
+  DEBUGASSERT(up_interrupt_context() == false);
+
+  /* Verify the input parameters and, in case of an error, set
+   * errno appropriately.
+   */
+
+#ifdef CONFIG_DEBUG
+  if (!abstime || !sem)
+    {
+      err = EINVAL;
+      goto errout;
+    }
+#endif
+
+  /* Create a watchdog.  We will not actually need this watchdog
+   * unless the the semaphore is unavailable, but we will reserve it up
+   * front before we enter the following critical section.
+   */
+
+  wdog = wd_create();
+  if (!wdog)
+    {
+      err = ENOMEM;
+      goto errout;
+    }
+
+  /* We will disable interrupts until we have completed the semaphore
+   * wait.  We need to do this (as opposed to just disabling pre-emption)
+   * because there could be interrupt handlers that are asynchronoulsy
+   * posting semaphores and to prevent race conditions with watchdog
+   * timeout.  This is not too bad because interrupts will be re-
+   * enabled while we are blocked waiting for the semaphore.
+   */
+
+  flags = irqsave();
+
+  /* Try to take the semaphore without waiting. */
+
+  ret = sem_trywait(sem);
+  if (ret == 0)
+    {
+      /* We got it! */
+
+      irqrestore(flags);
+      wd_delete(wdog);
+      return OK;
+    }
+
+  /* We will have to wait for the semphore.  Make sure that we were provided
+   * with a valid timeout.
+   */
+
+  if (abstime->tv_sec < 0 || abstime->tv_nsec > 1000000000)
+    {
+      err = EINVAL;
+      goto errout_disabled;
+    }
+
+  /* Convert the timespec to clock ticks.  We must have interrupts
+   * disabled here so that this time stays valid until the wait begins.
+   */
+
+  err = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
+
+  /* If the time has already expired return immediately. */
+
+  if (err == OK && ticks <= 0)
+    {
+      err = ETIMEDOUT;
+      goto errout_disabled;
+    }
+
+  /* Handle any time-related errors */
+
+  if (err != OK)
+    {
+      goto errout_disabled;
+    }
+
+  /* Start the watchdog */
+
+  err = OK; 
+  wd_start(wdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
+
+  /* Now perform the blocking wait */
+
+  ret = sem_wait(sem);
+
+  /* Stop the watchdog timer */
+
+  wd_cancel(wdog);
+
+  /* We can now restore interrupts and delete the watchdog */
+
+  irqrestore(flags);
+  wd_delete(wdog);
+
+  /* We are either returning success or an error detected by sem_wait()
+   * or the timeout detected by sem_timeout().
+   */
+
+  return ret;
+
+/* Error exits */
+
+errout_disabled:
+  irqrestore(flags);
+  wd_delete(wdog);
+errout:
+  set_errno(err);
+  return ERROR;
+}