lib/timer: add fallback if timer_create() not available

* add struct ul_timer as API abstraction to hide differences between
timer_create() and setitimer()

* add setitimer() detection to ./configure.ac

* add fallback code to use setitimer() if timer_create() not available
  (for example on OSX)

Addresses: https://github.com/karelzak/util-linux/issues/584
Signed-off-by: Karel Zak <kzak@redhat.com>

configure.ac

@@ -558,6 +558,10 @@ AC_CHECK_FUNCS([timer_create],
 
 AC_SUBST([REALTIME_LIBS])
 
+AS_IF([test x"$have_timer" = xno], [
+       AC_CHECK_FUNCS([setitimer], [have_timer="yes"], [have_timer="no"])
+])
+
 
 AC_CHECK_LIB([rtas], [rtas_get_sysparm], [
 	RTAS_LIBS="-lrtas"

include/timer.h

@@ -4,8 +4,19 @@
 #include <signal.h>
 #include <sys/time.h>
 
-extern int setup_timer(timer_t * t_id, struct itimerval *timeout,
+#ifdef HAVE_TIMER_CREATE
+struct ul_timer {
+	timer_t t_id;
+};
+#else
+struct ul_timer {
+	struct itimerval old_timer;
+	struct sigaction old_sa;
+};
+#endif
+
+extern int setup_timer(struct ul_timer *timer, struct itimerval *timeout,
 		       void (*timeout_handler)(int, siginfo_t *, void *));
-extern void cancel_timer(timer_t * t_id);
+extern void cancel_timer(struct ul_timer *timer);
 
 #endif /* UTIL_LINUX_TIMER_H */

lib/timer.c

@@ -27,7 +27,9 @@
  * The applications need to ensure that they can tolerate multiple signal
  * deliveries.
  */
-int setup_timer(timer_t * t_id, struct itimerval *timeout,
+#ifdef HAVE_TIMER_CREATE
+int setup_timer(struct ul_timer *timer,
+		struct itimerval *timeout,
 		void (*timeout_handler)(int, siginfo_t *, void *))
 {
 	time_t sec = timeout->it_value.tv_sec;
@@ -52,14 +54,42 @@ int setup_timer(timer_t * t_id, struct itimerval *timeout,
 
 	if (sigaction(SIGALRM, &sig_a, NULL))
 		return 1;
-	if (timer_create(CLOCK_MONOTONIC, &sig_e, t_id))
+	if (timer_create(CLOCK_MONOTONIC, &sig_e, &timer->t_id))
 		return 1;
-	if (timer_settime(*t_id, 0, &val, NULL))
+	if (timer_settime(timer->t_id, 0, &val, NULL))
+		return 1;
+	return 0;
+}
+void cancel_timer(struct ul_timer *timer)
+{
+	timer_delete(timer->t_id);
+}
+
+#else /* !HAVE_TIMER_CREATE */
+
+int setup_timer(struct ul_timer *timer,
+		struct itimerval *timeout,
+		void (*timeout_handler)(int, siginfo_t *, void *))
+{
+	struct sigaction sa;
+
+	memset(&sa, 0, sizeof sa);
+	memset(timer, 0, sizeof(*timer));
+
+	sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
+	sa.sa_sigaction = timeout_handler;
+
+	if (sigaction(SIGALRM, &sa, &timer->old_sa))
+		return 1;
+	if (setitimer(ITIMER_REAL, timeout, &timer->old_timer) != 0)
 		return 1;
 	return 0;
 }
 
-void cancel_timer(timer_t *t_id)
+void cancel_timer(struct ul_timer *timer)
 {
-	timer_delete(*t_id);
+	setitimer(ITIMER_REAL, &timer->old_timer, NULL);
+        sigaction(SIGALRM, &timer->old_sa, NULL);
+
 }
+#endif /* !HAVE_TIMER_CREATE */

misc-utils/uuidd.c

@@ -298,7 +298,9 @@ static void timeout_handler(int sig __attribute__((__unused__)),
 			    siginfo_t * info,
 			    void *context __attribute__((__unused__)))
 {
+#ifdef HAVE_TIMER_CREATE
 	if (info->si_code == SI_TIMER)
+#endif
 		errx(EXIT_FAILURE, _("timed out"));
 }
 
@@ -327,18 +329,18 @@ static void server_loop(const char *socket_path, const char *pidfile_path,
 	if (!uuidd_cxt->no_sock)	/* no_sock implies no_fork and no_pid */
 #endif
 	{
-		static timer_t t_id;
+		struct ul_timer timer;
 		struct itimerval timeout;
 
 		memset(&timeout, 0, sizeof timeout);
 		timeout.it_value.tv_sec = 30;
-		if (setup_timer(&t_id, &timeout, &timeout_handler))
+		if (setup_timer(&timer, &timeout, &timeout_handler))
 			err(EXIT_FAILURE, _("cannot set up timer"));
 		if (pidfile_path)
 			fd_pidfile = create_pidfile(uuidd_cxt, pidfile_path);
 		ret = call_daemon(socket_path, UUIDD_OP_GETPID, reply_buf,
 				  sizeof(reply_buf), 0, NULL);
-		cancel_timer(&t_id);
+		cancel_timer(&timer);
 		if (ret > 0) {
 			if (!uuidd_cxt->quiet)
 				warnx(_("uuidd daemon is already running at pid %s"),

sys-utils/flock.c

@@ -81,7 +81,9 @@ static void timeout_handler(int sig __attribute__((__unused__)),
 			    siginfo_t *info,
 			    void *context __attribute__((__unused__)))
 {
+#ifdef HAVE_TIMER_CREATE
 	if (info->si_code == SI_TIMER)
+#endif
 		timeout_expired = 1;
 }
 
@@ -124,7 +126,7 @@ static void __attribute__((__noreturn__)) run_program(char **cmd_argv)
 
 int main(int argc, char *argv[])
 {
-	static timer_t t_id;
+	struct ul_timer timer;
 	struct itimerval timeout;
 	int have_timeout = 0;
 	int type = LOCK_EX;
@@ -268,7 +270,7 @@ int main(int argc, char *argv[])
 			have_timeout = 0;
 			block = LOCK_NB;
 		} else
-			if (setup_timer(&t_id, &timeout, &timeout_handler))
+			if (setup_timer(&timer, &timeout, &timeout_handler))
 				err(EX_OSERR, _("cannot set up timer"));
 	}
 
@@ -321,7 +323,7 @@ int main(int argc, char *argv[])
 	}
 
 	if (have_timeout)
-		cancel_timer(&t_id);
+		cancel_timer(&timer);
 	if (verbose) {
 		struct timeval delta;