Include xtime.h and gethrxtime.h, not xalloc.h.

(timespec_subtract): Remove.
(NANOSLEEP_BUG_WORKAROUND): New constant.
(xnanosleep): Use gethrxtime rather than gettime; this simplifies
things considerably.  Use it only on GNU/Linux hosts, since the
workaround shouldn't be needed elsewhere.

1 files changed, 54 insertions, 80 deletions

diff --git a/lib/xnanosleep.c b/lib/xnanosleep.c
index 6ca43e560..8aa5e8a8d 100644
--- a/lib/xnanosleep.c
+++ b/lib/xnanosleep.c
@@ -1,5 +1,5 @@
 /* xnanosleep.c -- a more convenient interface to nanosleep
-   Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -32,6 +32,10 @@
 #include <sys/types.h>
 #include <time.h>
 
+#include "timespec.h"
+#include "gethrxtime.h"
+#include "xtime.h"
+
 /* The extra casts work around common compiler bugs.  */
 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
@@ -44,44 +48,18 @@
 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
 #endif
 
-#include "timespec.h"
-#include "xalloc.h"
-
-/* Subtract the `struct timespec' values X and Y by computing X - Y.
-   If the difference is negative or zero, return false.
-   Otherwise, return true and store the difference in DIFF.
-   X and Y must have valid ts_nsec values, in the range 0 to 999999999.
-   If the difference would overflow, store the maximum possible difference.  */
-
-static bool
-timespec_subtract (struct timespec *diff,
-		   struct timespec const *x, struct timespec const *y)
-{
-  time_t sec = x->tv_sec - y->tv_sec;
-  long int nsec = x->tv_nsec - y->tv_nsec;
-
-  if (x->tv_sec < y->tv_sec)
-    return false;
-
-  if (sec < 0)
-    {
-      /* The difference has overflowed.  */
-      sec = TIME_T_MAX;
-      nsec = 999999999;
-    }
-  else if (sec == 0 && nsec <= 0)
-    return false;
-
-  if (nsec < 0)
-    {
-      sec--;
-      nsec += 1000000000;
-    }
-
-  diff->tv_sec = sec;
-  diff->tv_nsec = nsec;
-  return true;
-}
+/* POSIX.1-2001 requires that when a process is suspended, then
+   resumed, nanosleep (A, B) returns -1, sets errno to EINTR, and sets
+   *B to the time remaining at the point of resumption.  However, some
+   versions of the Linux kernel incorrectly return the time remaining
+   at the point of suspension.  Work around this bug on GNU/Linux
+   hosts by computing the remaining time here after nanosleep returns,
+   rather than by relying on nanosleep's computation.  */
+#ifdef __linux__
+enum { NANOSLEEP_BUG_WORKAROUND = true };
+#else
+enum { NANOSLEEP_BUG_WORKAROUND = false };
+#endif
 
 /* Sleep until the time (call it WAKE_UP_TIME) specified as
    SECONDS seconds after the time this function is called.
@@ -93,22 +71,29 @@ timespec_subtract (struct timespec *diff,
 int
 xnanosleep (double seconds)
 {
-  bool overflow;
+  enum { BILLION = 1000000000 };
+
+  bool overflow = false;
   double ns;
-  struct timespec ts_start;
   struct timespec ts_sleep;
-  struct timespec ts_stop;
+  xtime_t stop = 0;
 
   assert (0 <= seconds);
 
-  if (gettime (&ts_start) != 0)
-    return -1;
+  if (NANOSLEEP_BUG_WORKAROUND)
+    {
+      xtime_t now = gethrxtime ();
+      double increment = XTIME_PRECISION * seconds;
+      xtime_t incr = increment;
+      stop = now + incr + (incr < increment);
+      overflow = (stop < now);
+    }
 
   /* Separate whole seconds from nanoseconds.
      Be careful to detect any overflow.  */
   ts_sleep.tv_sec = seconds;
-  ns = 1e9 * (seconds - ts_sleep.tv_sec);
-  overflow = ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= 1e9);
+  ns = BILLION * (seconds - ts_sleep.tv_sec);
+  overflow |= ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= BILLION);
   ts_sleep.tv_nsec = ns;
 
   /* Round up to the next whole number, if necessary, so that we
@@ -119,7 +104,7 @@ xnanosleep (double seconds)
   ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
 
   /* Normalize the interval length.  nanosleep requires this.  */
-  if (1000000000 <= ts_sleep.tv_nsec)
+  if (BILLION <= ts_sleep.tv_nsec)
     {
       time_t t = ts_sleep.tv_sec + 1;
 
@@ -127,45 +112,34 @@ xnanosleep (double seconds)
       overflow |= (t < ts_sleep.tv_sec);
 
       ts_sleep.tv_sec = t;
-      ts_sleep.tv_nsec -= 1000000000;
-    }
-
-  /* Compute the time until which we should sleep.  */
-  ts_stop.tv_sec = ts_start.tv_sec + ts_sleep.tv_sec;
-  ts_stop.tv_nsec = ts_start.tv_nsec + ts_sleep.tv_nsec;
-  if (1000000000 <= ts_stop.tv_nsec)
-    {
-      ++ts_stop.tv_sec;
-      ts_stop.tv_nsec -= 1000000000;
+      ts_sleep.tv_nsec -= BILLION;
     }
 
-  /* Detect integer overflow.  */
-  overflow |= (ts_stop.tv_sec < ts_start.tv_sec
-	       || (ts_stop.tv_sec == ts_start.tv_sec
-		   && ts_stop.tv_nsec < ts_start.tv_nsec));
-
-  if (overflow)
+  for (;;)
     {
-      /* Fix ts_sleep and ts_stop, which may be garbage due to overflow.  */
-      ts_sleep.tv_sec = ts_stop.tv_sec = TIME_T_MAX;
-      ts_sleep.tv_nsec = ts_stop.tv_nsec = 999999999;
-    }
+      if (overflow)
+	{
+	  ts_sleep.tv_sec = TIME_T_MAX;
+	  ts_sleep.tv_nsec = BILLION - 1;
+	}
 
-  while (nanosleep (&ts_sleep, NULL) != 0)
-    {
-      if (errno != EINTR || gettime (&ts_start) != 0)
+      if (nanosleep (&ts_sleep, NULL) == 0)
+	break;
+      if (errno != EINTR)
 	return -1;
 
-      /* POSIX.1-2001 requires that when a process is suspended, then
-	 resumed, nanosleep (A, B) returns -1, sets errno to EINTR,
-	 and sets *B to the time remaining at the point of resumption.
-	 However, some versions of the Linux kernel incorrectly return
-	 the time remaining at the point of suspension.  Work around
-	 this bug by computing the remaining time here, rather than by
-	 relying on nanosleep's computation.  */
-
-      if (! timespec_subtract (&ts_sleep, &ts_stop, &ts_start))
-	break;
+      if (NANOSLEEP_BUG_WORKAROUND)
+	{
+	  xtime_t now = gethrxtime ();
+	  if (stop <= now)
+	    break;
+	  else
+	    {
+	      xtime_t remaining = stop - now;
+	      ts_sleep.tv_sec = xtime_nonnegative_sec (remaining);
+	      ts_sleep.tv_nsec = xtime_nonnegative_nsec (remaining);
+	    }
+	}
     }
 
   return 0;