include/c.h: prefer nanosleep() over usleep()

Let's use nanosleep() although if usleep() exists. The nanosleep
function does no interact with signals and other timers.

The patch introduces xusleep() as replacement to libc (or our fallback)
usleep(). Yes, we don't want to use struct timespec + nanosleep()
everywhere in code as nano-time resolution is useless for us.

The patch also enlarges delays in some busy wait loops. It seems
enough to try read/write 4x per second.

Signed-off-by: Karel Zak <kzak@redhat.com>

include/all-io.h

@@ -29,7 +29,7 @@ static inline int write_all(int fd, const void *buf, size_t count)
 		} else if (errno != EINTR && errno != EAGAIN)
 			return -1;
 		if (errno == EAGAIN)	/* Try later, *sigh* */
-			usleep(10000);
+			xusleep(250000);
 	}
 	return 0;
 }
@@ -49,7 +49,7 @@ static inline int fwrite_all(const void *ptr, size_t size,
 		} else if (errno != EINTR && errno != EAGAIN)
 			return -1;
 		if (errno == EAGAIN)	/* Try later, *sigh* */
-			usleep(10000);
+			xusleep(250000);
 	}
 	return 0;
 }
@@ -65,8 +65,10 @@ static inline ssize_t read_all(int fd, char *buf, size_t count)
 		ret = read(fd, buf, count);
 		if (ret <= 0) {
 			if ((errno == EAGAIN || errno == EINTR || ret == 0) &&
-			    (tries++ < 5))
+			    (tries++ < 5)) {
+				xusleep(250000);
 				continue;
+			}
 			return c ? c : -1;
 		}
 		if (ret > 0)

include/c.h

@@ -253,20 +253,27 @@ static inline size_t get_hostname_max(void)
 	return 64;
 }
 
-#ifndef HAVE_USLEEP
 /*
- * This function is marked obsolete in POSIX.1-2001 and removed in
- * POSIX.1-2008. It is replaced with nanosleep().
+ * The usleep function is marked obsolete in POSIX.1-2001 and removed in
+ * POSIX.1-2008. This is replaced with nanosleep() that provides more
+ * advantages (like no interaction with signals and other timer functions.
  */
-static inline int usleep(useconds_t usec)
+#include <time.h>
+
+static inline int xusleep(useconds_t usec)
 {
+#ifdef HAVE_NANOSLEEP
 	struct timespec waittime = {
 		.tv_sec   =  usec / 1000000L,
 		.tv_nsec  = (usec % 1000000L) * 1000
 	};
 	return nanosleep(&waittime, NULL);
-}
+#elif defined(HAVE_USLEEP)
+	return usleep(usec);
+#else
+# error	"System with usleep() or nanosleep() required!"
 #endif
+}
 
 /*
  * Constant strings for usage() functions. For more info see

libmount/src/lock.c

@@ -650,7 +650,7 @@ int test_lock(struct libmnt_test *ts, int argc, char *argv[])
 		if (synctime && synctime - tv.tv_sec > 1) {
 			usecs = ((synctime - tv.tv_sec) * 1000000UL) -
 						(1000000UL - tv.tv_usec);
-			usleep(usecs);
+			xusleep(usecs);
 		}
 	}
 
@@ -676,7 +676,7 @@ int test_lock(struct libmnt_test *ts, int argc, char *argv[])
 		 * concurrent processes happy.
 		 */
 		if (synctime)
-			usleep(25000);
+			xusleep(25000);
 	}
 
 	return 0;

login-utils/sulogin.c

@@ -590,7 +590,7 @@ static char *getpasswd(struct console *con)
 	while (cp->eol == '\0') {
 		if (read(fd, &c, 1) < 1) {
 			if (errno == EINTR || errno == EAGAIN) {
-				usleep(1000);
+				xusleep(250000);
 				continue;
 			}
 			ret = (char*)0;
@@ -993,7 +993,7 @@ int main(int argc, char **argv)
 			if (*usemask & (1<<con->id))
 				continue;
 			kill(con->pid, SIGHUP);
-			usleep(5000);
+			usleep(50000);
 			kill(con->pid, SIGKILL);
 		}
 	}

sys-utils/hwclock-kd.c

@@ -66,7 +66,7 @@ static int synchronize_to_clock_tick_kd(void)
 		 *  A2000 RTCs and simply hangs after some time. Inserting a
 		 *  sleep helps."
 		 */
-		usleep(1);
+		xusleep(1);
 
 		if (ioctl(con_fd, KDGHWCLK, &nowtime) == -1) {
 			warn(_("KDGHWCLK ioctl to read time failed in loop"));

sys-utils/rtcwake.c

@@ -560,7 +560,7 @@ int main(int argc, char **argv)
 				program_invocation_short_name, suspend, devname,
 				ctime(&alarm));
 		fflush(stdout);
-		usleep(10 * 1000);
+		xusleep(10 * 1000);
 	}
 
 	if (strcmp(suspend, "no") == 0) {

term-utils/agetty.c

@@ -1589,7 +1589,7 @@ static char *get_logname(struct options *op, struct termios *tp, struct chardata
 				/* The terminal could be open with O_NONBLOCK when
 				 * -L (force CLOCAL) is specified...  */
 				if (errno == EINTR || errno == EAGAIN) {
-					usleep(250000);
+					xusleep(250000);
 					continue;
 				}
 				switch (errno) {

text-utils/tailf.c

@@ -133,7 +133,7 @@ watch_file(const char *filename, off_t *size)
 {
 	do {
 		roll_file(filename, size);
-		usleep(250000);
+		xusleep(250000);
 	} while(1);
 }