/*
* Common RTC functions
*
- * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "libbb.h"
char buffer[128];
while (fgets(buffer, sizeof(buffer), f)) {
- if (strncmp(buffer, "UTC", 3) == 0) {
+ if (is_prefixed_with(buffer, "UTC")) {
utc = 1;
break;
}
return utc;
}
+/* rtc opens are exclusive.
+ * Try to run two "hwclock -w" at the same time to see it.
+ * Users wouldn't expect that to fail merely because /dev/rtc
+ * was momentarily busy, let's try a bit harder on errno == EBUSY.
+ */
+static int open_loop_on_busy(const char *name, int flags)
+{
+ int rtc;
+ /*
+ * Tested with two parallel "hwclock -w" loops.
+ * With try = 10, no failures with 2x1000000 loop iterations.
+ */
+ int try = 1000 / 20;
+ again:
+ errno = 0;
+ rtc = open(name, flags);
+ if (errno == EBUSY) {
+ usleep(20 * 1000);
+ if (--try != 0)
+ goto again;
+ /* EBUSY. Last try, exit on error instead of returning -1 */
+ return xopen(name, flags);
+ }
+ return rtc;
+}
+
+/* Never fails */
int FAST_FUNC rtc_xopen(const char **default_rtc, int flags)
{
int rtc;
+ const char *name =
+ "/dev/rtc""\0"
+ "/dev/rtc0""\0"
+ "/dev/misc/rtc""\0";
- if (!*default_rtc) {
- *default_rtc = "/dev/rtc";
- rtc = open(*default_rtc, flags);
- if (rtc >= 0)
- return rtc;
- *default_rtc = "/dev/rtc0";
- rtc = open(*default_rtc, flags);
+ if (!*default_rtc)
+ goto try_name;
+ name = ""; /*else: we have rtc name, don't try other names */
+
+ for (;;) {
+ rtc = open_loop_on_busy(*default_rtc, flags);
if (rtc >= 0)
return rtc;
- *default_rtc = "/dev/misc/rtc";
+ if (!name[0])
+ return xopen(*default_rtc, flags);
+ try_name:
+ *default_rtc = name;
+ name += strlen(name) + 1;
}
-
- return xopen(*default_rtc, flags);
}
void FAST_FUNC rtc_read_tm(struct tm *ptm, int fd)