NuttX RTOS

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 306 insertions, 0 deletions

diff --git a/nuttx/sched/pthread_condtimedwait.c b/nuttx/sched/pthread_condtimedwait.c
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+++ b/nuttx/sched/pthread_condtimedwait.c
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+/************************************************************
+ * pthread_condtimedwait.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 <sys/types.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <signal.h>
+#include <time.h>
+#include <errno.h>
+#include <wdog.h>
+#include <debug.h>
+#include "os_internal.h"
+#include "pthread_internal.h"
+#include "clock_internal.h"
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+#define ECHO_COND_WAIT_SIGNO 3
+
+/************************************************************
+ * Private Type Declarations
+ ************************************************************/
+
+/************************************************************
+ * Global Variables
+ ************************************************************/
+
+/************************************************************
+ * Private Variables
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+static void pthread_condtimedout(int pid, int signo, int arg3, int arg4)
+{
+  union sigval value;
+
+  /* Send the specified signal to the specified task. */
+
+  value.sival_ptr = 0;
+  (void)sigqueue(pid, signo, value);
+}
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Function:  pthread_cond_timedwait
+ *
+ * Description:
+ *   A thread can perform a timed wait on a condition variable.
+ *
+ * Parameters:
+ *   None
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions:
+ *   Timing is of resolution 1 msec, with +/-1 millisecond
+ *   accuracy.
+ *
+ ************************************************************/
+
+int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
+                           const struct timespec *abstime)
+{
+  struct timespec currtime;
+  struct timespec reltime;
+  WDOG_ID         wdog;
+  sint32          relusec;
+  sint32          ticks;
+  int             mypid = (int)getpid();
+  int             ret = OK;
+  int             int_state;
+  int             status;
+
+  dbg("%s: cond=0x%p mutex=0x%p abstime=0x%p\n",
+      __FUNCTION__, cond, mutex, abstime);
+
+  /* Make sure that non-NULL references were provided. */
+
+  if (!cond || !mutex)
+    {
+      ret = EINVAL;
+    }
+
+  /* Make sure that the caller holds the mutex */
+
+  else if (mutex->pid != mypid)
+    {
+      ret = EPERM;
+    }
+
+  /* If no wait time is provided, this function degenerates to
+   * the same behavior as pthread_cond_wait().
+   */
+
+  else if (!abstime)
+    {
+      ret = pthread_cond_wait(cond, mutex);
+    }
+
+  else
+    {
+      /* Create a watchdog */
+
+      wdog = wd_create();
+      if (!wdog)
+        {
+          ret = EINVAL;
+        }
+      else
+        {
+          dbg("%s: Give up mutex...\n", __FUNCTION__);
+
+          /* We must disable pre-emption and interrupts here so that
+           * the time stays valid until the wait begins.   This adds
+           * complexity because we assure that interrupts and
+           * pre-emption are re-enabled correctly.
+           */
+
+          sched_lock();
+          int_state = irqsave();
+
+          /* Convert the timespec to clock ticks.  We must disable pre-emption
+           * here so that this time stays valid until the wait begins.
+           * NOTE:  Here we use internal knowledge that CLOCK_REALTIME is
+           * defined to be zero!
+           */
+
+          ret = clock_gettime(0, &currtime);
+          if (ret)
+            {
+              /* Restore interrupts  (pre-emption will be enabled when
+               * we fall through the if/then/else
+               */
+
+              irqrestore(int_state);
+            }
+          else
+            {
+              /* The relative time to wait is the absolute time minus the
+               * the current time.
+               */
+
+              reltime.tv_nsec = (abstime->tv_nsec - currtime.tv_nsec);
+              reltime.tv_sec  = (abstime->tv_sec  - currtime.tv_sec);
+
+              /* Check if we were supposed to borrow from the seconds
+               * to borrow from the seconds
+               */
+
+              if (reltime.tv_nsec < 0)
+                {
+                  reltime.tv_nsec += NSEC_PER_SEC;
+                  reltime.tv_sec  -= 1;
+                }
+
+              /* Convert this relative time into microseconds.*/
+
+              relusec =
+                reltime.tv_sec * USEC_PER_SEC +
+                reltime.tv_nsec / NSEC_PER_USEC;
+
+              /* Convert microseconds to clock ticks */
+
+              ticks = relusec / USEC_PER_TICK;
+
+              /* Check the absolute time to wait.  If it is now or in the past, then
+               * just return with the timedout condition.
+               */
+
+              if (ticks <= 0)
+                {
+                  /* Restore interrupts and indicate that we have already timed out.
+                   * (pre-emption will be enabled when we fall through the
+                   * if/then/else
+                   */
+
+                  irqrestore(int_state);
+                  ret = ETIMEDOUT;
+                }
+              else
+                {
+                  /* Give up the mutex */
+
+                  mutex->pid = 0;
+                  ret = pthread_givesemaphore((sem_t*)&mutex->sem);
+                  if (ret)
+                    {
+                      /* Restore interrupts  (pre-emption will be enabled when
+                       * we fall through the if/then/else)
+                       */
+
+                      irqrestore(int_state);
+                    }
+                  else
+                    {
+                      /* Start the watchdog */
+
+                      wd_start(wdog, ticks, (wdentry_t)pthread_condtimedout,
+                               mypid, ECHO_COND_WAIT_SIGNO, 0, 0);
+
+                      /* Take the condition semaphore.  Do not restore interrupts
+                       * until we return from the wait.  This is necessary to
+                       * make sure that the watchdog timer and the condition wait
+                       * are started atomically.
+                       */
+
+                      status = sem_wait((sem_t*)&cond->sem);
+                      irqrestore(int_state);
+
+                      /* Did we get the condition semaphore. */
+
+                      if (status != OK)
+                        {
+                          /* NO.. Handle the special case where the semaphore wait was
+                           * awakened by the receipt of a signal -- presumably the
+                           * signal posted by pthread_condtimedout().
+                           */
+
+                          if (*get_errno_ptr() == EINTR)
+                            {
+                              dbg("%s: Timedout!\n", __FUNCTION__);
+                              ret = ETIMEDOUT;
+                            }
+                          else
+                            {
+                              ret = EINVAL;
+                            }
+                        }
+                    }
+
+                  /* Reacquire the mutex (retaining the ret). */
+
+                  dbg("%s: Re-locking...\n", __FUNCTION__);
+                  status = pthread_takesemaphore((sem_t*)&mutex->sem);
+                  if (!status)
+                    {
+                      mutex->pid = mypid;
+                    }
+                  else if (!ret)
+                    {
+                      ret = status;
+                    }
+                }
+
+              /* Re-enable pre-emption (It is expected that interrupts
+               * have already been re-enabled in the above logic)
+               */
+
+              sched_unlock();
+            }
+
+          /* We no longer need the watchdog */
+
+          wd_delete(wdog);
+        }
+    }
+
+  dbg("%s: Returning %d\n", __FUNCTION__, ret);
+  return ret;
+}
+