commit f6042ca2e240a27a20e405de49755f350ca95e7b
Author: Sergey Poznyakoff <gray@gnu.org>
Date:   Sat Jul 25 22:15:56 2026 +0300

    Use nanosleep on systems lacking clock_nanosleep.
    
    * configure.ac: Check for clock_nanosleep.
    * src/progman.c (abswait): New function.
    (process_drain): Use it to wait till the specified absolute timestamp.

diff --git a/configure.ac b/configure.ac
index 336aa2a..a4fcedc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,7 +41,7 @@ AC_CHECK_HEADERS([sys/inotify.h sys/event.h])
 # Checks for typedefs, structures, and compiler characteristics.
 
 # Checks for library functions.
-AC_CHECK_FUNCS([inotify_init kqueue rfork getgrouplist])
+AC_CHECK_FUNCS([inotify_init kqueue rfork getgrouplist clock_nanosleep])
 
 if test "$ac_cv_header_sys_inotify_h/$ac_cv_func_inotify_init" = yes/yes; then
   iface=inotify
diff --git a/src/progman.c b/src/progman.c
index 86c3edf..743b97f 100644
--- a/src/progman.c
+++ b/src/progman.c
@@ -244,12 +244,40 @@ timespec_add(struct timespec *a, struct timespec *b)
 	}
 }
 
+static inline void
+timespec_sub(struct timespec *a, struct timespec const *b)
+{
+	struct timespec d;
+
+	a->tv_sec -= b->tv_sec;
+	a->tv_nsec -= b->tv_nsec;
+	if (a->tv_nsec < 0) {
+		--a->tv_sec;
+		a->tv_nsec += NANOSEC;
+	}
+}
+
+static int
+abswait(struct timespec const *ts)
+{
+#if HAVE_CLOCK_NANOSLEEP
+	return clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, ts, NULL);
+#else
+	struct timespec now, t = *ts;
+	clock_gettime(CLOCK_MONOTONIC, &now);
+	timespec_sub(&t, &now);
+	if (t.tv_sec < 0)
+		return 0;
+	return nanosleep(&t, NULL);
+#endif
+}
+
 void
 process_drain(void)
 {
 	struct process *p;
 	struct timespec ts;
-	
+
 	/* Send all processes the TERM signal. */
 	for (p = proc_list; p; p = p->next) {
 		if (p->type == PROC_HANDLER)
@@ -257,15 +285,13 @@ process_drain(void)
 	}
 	/* Wait for all processes to terminate. */
 	diag(LOG_INFO, _("waiting for processes to terminate"));
-		     
+
 	clock_gettime (CLOCK_MONOTONIC, &ts);
 	timespec_add (&ts, &shutdown_timeout);
-	
-	do {		
-		process_cleanup(1);
-	} while (proc_list &&
-		 clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts, NULL));
 
+	do {
+		process_cleanup(1);
+	} while (proc_list && abswait(&ts));
 
 	if (proc_list) {
 		diag(LOG_INFO,