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diff --git a/nuttx/sched/sleep.c b/nuttx/sched/sleep.c
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+/****************************************************************************
+ * sched/sleep.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 <unistd.h>
+#include <signal.h>
+
+#include <nuttx/clock.h>
+#include <arch/irq.h>
+
+/****************************************************************************
+ * Preprocessor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sleep
+ *
+ * Description:
+ *   The sleep() function will cause the calling thread to be suspended from
+ *   execution until either the number of real-time seconds specified by the
+ *   argument 'seconds' has elapsed or a signal is delivered to the calling
+ *   thread and its action is to invoke a signal-catching function or to
+ *   terminate the process. The suspension time may be longer than requested
+ *   due to the scheduling of other activity by the system.
+ *
+ *   If a SIGALRM signal is generated for the calling process during
+ *   execution of sleep() and if the SIGALRM signal is being ignored or
+ *   blocked from delivery, it is unspecified whether sleep() returns
+ *   when the SIGALRM signal is scheduled. If the signal is being blocked, it
+ *   is also unspecified whether it remains pending after sleep() returns or
+ *   it is discarded.
+ *
+ *   If a SIGALRM signal is generated for the calling process during
+ *   execution of sleep(), except as a result of a prior call to alarm(),
+ *   and if the SIGALRM signal is not being ignored or blocked from delivery,
+ *   it is unspecified whether that signal has any effect other than causing
+ *   sleep() to return.
+ *
+ *   If a signal-catching function interrupts sleep() and examines or changes
+ *   either the time a SIGALRM is scheduled to be generated, the action
+ *   associated with the SIGALRM signal, or whether the SIGALRM signal is
+ *   blocked from delivery, the results are unspecified.
+ *
+ *   If a signal-catching function interrupts sleep() and calls siglongjmp()
+ *   or longjmp() to restore an environment saved prior to the sleep() call,
+ *   the action associated with the SIGALRM signal and the time at which a
+ *   SIGALRM signal is scheduled to be generated are unspecified. It is also
+ *   unspecified whether the SIGALRM signal is blocked, unless the process'
+ *   signal mask is restored as part of the environment.
+ *
+ *   Implementations may place limitations on the granularity of timer values.
+ *   For each interval timer, if the requested timer value requires a finer
+ *   granularity than the implementation supports, the actual timer value will
+ *   be rounded up to the next supported value. 
+ *
+ *   Interactions between sleep() and any of setitimer(), ualarm() or sleep()
+ *   are unspecified. 
+ *
+ * Parameters:
+ *   seconds
+ *
+ * Returned Value:
+ *   If sleep() returns because the requested time has elapsed, the value
+ *   returned will be 0. If sleep() returns because of premature arousal due
+ *   to delivery of a signal, the return value will be the "unslept" amount
+ *   (the requested time minus the time actually slept) in seconds.
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+unsigned int sleep(unsigned int seconds)
+{
+  sigset_t set;
+  struct timespec ts;
+  struct siginfo value;
+  irqstate_t flags;
+  uint32_t start;
+  int32_t elapsed;
+  int32_t remaining = 0;
+
+  /* Don't sleep if seconds == 0 */
+
+  if (seconds)
+    {
+      /* Set up for the sleep.  Using the empty set means that we are not
+       * waiting for any particualar signal.  However, any unmasked signal
+       * can still awaken sigtimedwait().
+       */
+
+      (void)sigemptyset(&set);
+      ts.tv_sec  = seconds;
+      ts.tv_nsec = 0;
+
+      /* Interrupts are disabled around the following so that it is atomic */
+       
+      flags = irqsave();
+ 
+      /* Get the current time then sleep for the requested time.  
+       * sigtimedwait() cannot succeed.  It should always return error with
+       * either (1) EAGAIN meaning that the timeout occurred, or (2) EINTR
+       * meaning that some other unblocked signal was caught.
+       */
+
+      start = clock_systimer();
+      (void)sigtimedwait(&set, &value, &ts);
+
+      /* Calculate the elapsed time (in clock ticks) when we wake up from the sleep.
+       * This is really only necessary if we were awakened from the sleep early
+       * due to the receipt of a signal.
+       */
+
+      elapsed = clock_systimer() - start;
+      irqrestore(flags);
+
+      /* Get the remaining, un-waited seconds. Note that this calculation
+       * truncates the elapsed seconds in the division.  We may have slept some
+       * fraction of a second longer than this!  But if the calculation is less
+       * than the 'seconds', we certainly did not sleep for the complete
+       * requested interval.
+       */
+
+      remaining = (int32_t)seconds - elapsed / TICK_PER_SEC;
+
+      /* Make sure that the elapsed time is non-negative (this should always
+       * be the case unless something exceptional happened while were we
+       * sleeping -- like the clock was reset or we went into a low power mode,
+       * OR if we had to wait a long time to run again after calling
+       * sigtimedwait() making 'elapsed' bigger than it should have been).
+       */
+
+      if (remaining < 0)
+        {
+          remaining = 0;
+        }
+    }
+
+  return (unsigned int)remaining;
+}