/* 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
#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.
# 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.
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
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;
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;
projects / gnulib.git / blobdiff