Remove workaround for bug in Linux kernel 2.6.8 or thereabouts.

The workaround isn't strictly needed for POSIX conformance, and
it's too much of a pain to configure and maintain.  We'll ask
people to fix their kernels instead.
* modules/xnanosleep (Depends-on): Remove gethrxtime.
* lib/xnanosleep.c: Don't include gethrxtime.h or xtime.h.
(NANOSLEEP_BUG_WORKAROUND): Remove.
(xnanosleep): Remove the workaround.
* m4/xnanosleep.m4 (gl_XNANOSLEEP): Remove configuration attempting
to detect nanosleep bug.

1 files changed, 8 insertions, 39 deletions

diff --git a/lib/xnanosleep.c b/lib/xnanosleep.c
index 8aa5e8a8de..fcfe3d551d 100644
--- a/lib/xnanosleep.c
+++ b/lib/xnanosleep.c
@@ -33,8 +33,6 @@
 #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))
@@ -48,19 +46,6 @@
 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
 #endif
 
-/* 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.
    SECONDS must be non-negative.  If SECONDS is so large that
@@ -76,19 +61,9 @@ xnanosleep (double seconds)
   bool overflow = false;
   double ns;
   struct timespec ts_sleep;
-  xtime_t stop = 0;
 
   assert (0 <= seconds);
 
-  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;
@@ -123,23 +98,17 @@ xnanosleep (double seconds)
 	  ts_sleep.tv_nsec = BILLION - 1;
 	}
 
+      /* Linux-2.6.8.1's nanosleep returns -1, but doesn't set errno
+	 when resumed after being suspended.  Earlier versions would
+	 set errno to EINTR.  nanosleep from linux-2.6.10, as well as
+	 implementations by (all?) other vendors, doesn't return -1
+	 in that case;  either it continues sleeping (if time remains)
+	 or it returns zero (if the wake-up time has passed).  */
+      errno = 0;
       if (nanosleep (&ts_sleep, NULL) == 0)
 	break;
-      if (errno != EINTR)
+      if (errno != EINTR && errno != 0)
 	return -1;
-
-      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;