hwclock: fix sizeof bug (used it on pointer, not array); make --systohc exact

[platform/upstream/busybox.git] / util-linux / hwclock.c

diff --git a/util-linux/hwclock.c b/util-linux/hwclock.c
index 6dff57f..08e5bd7 100644 (file)
--- a/util-linux/hwclock.c
+++ b/util-linux/hwclock.c
@@ -27,27 +27,12 @@ static time_t read_rtc(int utc)
 
        fd = rtc_xopen(&rtcname, O_RDONLY);
        ret = rtc_read_time(fd, utc);
-       close(fd);
+       if (ENABLE_FEATURE_CLEAN_UP)
+               close(fd);
 
        return ret;
 }
 
-static void write_rtc(time_t t, int utc)
-{
-       struct tm tm;
-       int rtc = rtc_xopen(&rtcname, O_WRONLY);
-
-       if (utc)
-               gmtime_r(&t, &tm);
-       else
-               localtime_r(&t, &tm);
-       tm.tm_isdst = 0;
-
-       xioctl(rtc, RTC_SET_TIME, &tm);
-
-       close(rtc);
-}
-
 static void show_clock(int utc)
 {
        //struct tm *ptm;
@@ -58,10 +43,10 @@ static void show_clock(int utc)
        //ptm = localtime(&t);  /* Sets 'tzname[]' */
 
        cp = ctime(&t);
-       if (cp[0])
-               cp[strlen(cp) - 1] = '\0';
+       strchrnul(cp, '\n')[0] = '\0';
 
-       //printf("%s  %.6f seconds %s\n", cp, 0.0, utc ? "" : (ptm->tm_isdst ? tzname[1] : tzname[0]));
+       //printf("%s  0.000000 seconds %s\n", cp, utc ? "" : (ptm->tm_isdst ? tzname[1] : tzname[0]));
+       /* 0.000000 stand for unimplemented difference between RTC and system clock */
        printf("%s  0.000000 seconds\n", cp);
 }
 
@@ -81,12 +66,73 @@ static void to_sys_clock(int utc)
 
 static void from_sys_clock(int utc)
 {
+#define TWEAK_USEC 200
+       struct tm tm;
        struct timeval tv;
+       unsigned adj = TWEAK_USEC;
+       int rtc = rtc_xopen(&rtcname, O_WRONLY);
+
+       /* Try to catch the moment when whole second is close */
+       while (1) {
+               unsigned rem_usec;
+               time_t t;
+
+               gettimeofday(&tv, NULL);
+
+               rem_usec = 1000000 - tv.tv_usec;
+               if (rem_usec < 1024) {
+                       /* Less than 1ms to next second. Good enough */
+ small_rem:
+                       tv.tv_sec++;
+               }
+
+               /* Prepare tm */
+               t = tv.tv_sec;
+               if (utc)
+                       gmtime_r(&t, &tm); /* may read /etc/xxx (it takes time) */
+               else
+                       localtime_r(&t, &tm); /* same */
+               tm.tm_isdst = 0;
+
+               /* gmtime/localtime took some time, re-get cur time */
+               gettimeofday(&tv, NULL);
+
+               if (tv.tv_sec < t /* may happen if rem_usec was < 1024 */
+                || (tv.tv_sec == t && tv.tv_usec < 1024)
+               ) {
+                       /* We are not too far into next second. Good. */
+                       break;
+               }
+               adj += 32; /* 2^(10-5) = 2^5 = 32 iterations max */
+               if (adj >= 1024) {
+                       /* Give up trying to sync */
+                       break;
+               }
+
+               /* Try to sync up by sleeping */
+               rem_usec = 1000000 - tv.tv_usec;
+               if (rem_usec < 1024) {
+                       goto small_rem; /* already close, don't sleep */
+               }
+               /* Need to sleep.
+                * Note that small adj on slow processors can make us
+                * to always overshoot tv.tv_usec < 1024 check on next
+                * iteration. That's why adj is increased on each iteration.
+                * This also allows it to be reused as a loop limiter.
+                */
+               usleep(rem_usec - adj);
+       }
+
+       xioctl(rtc, RTC_SET_TIME, &tm);
+
+       /* Debug aid to find "good" TWEAK_USEC.
+        * Look for a value which makes tv_usec close to 999999 or 0.
+        * for 2.20GHz Intel Core 2: TWEAK_USEC ~= 200
+        */
+       //bb_error_msg("tv.tv_usec:%d adj:%d", (int)tv.tv_usec, adj);
 
-       gettimeofday(&tv, NULL);
-       //if (gettimeofday(&tv, NULL))
-       //      bb_perror_msg_and_die("gettimeofday() failed");
-       write_rtc(tv.tv_sec, utc);
+       if (ENABLE_FEATURE_CLEAN_UP)
+               close(rtc);
 }
 
 #define HWCLOCK_OPT_LOCALTIME   0x01