hwclock: don't open /dev/rtc repeatedly

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

diff --git a/hwclock/rtc.c b/hwclock/rtc.c
index 7ec5362e898eba8e665af7410bdb398c0c1dc943..2e053856a682ebf0cdd552d27c4df118ab37067e 100644 (file)
--- a/hwclock/rtc.c
+++ b/hwclock/rtc.c
@@ -92,6 +92,15 @@ struct linux_rtc_time {
 /* default or user defined dev (by hwclock --rtc=<path>) */
 char *rtc_dev_name;
 
+static int rtc_dev_fd = -1;
+
+static void
+close_rtc(void) {
+       if (rtc_dev_fd != -1)
+               close(rtc_dev_fd);
+       rtc_dev_fd = -1;
+}
+
 static int
 open_rtc(void) {
        char *fls[] = {
@@ -106,20 +115,28 @@ open_rtc(void) {
        };
        char **p;
 
+       if (rtc_dev_fd != -1)
+               return rtc_dev_fd;
+
        /* --rtc option has been given */
        if (rtc_dev_name)
-               return open(rtc_dev_name, O_RDONLY);
-
-       for (p=fls; *p; ++p) {
-               int fd = open(*p, O_RDONLY);
-
-               if (fd < 0 && (errno == ENOENT || errno == ENODEV))
-                       continue;
-               rtc_dev_name = *p;
-               return fd;
+               rtc_dev_fd = open(rtc_dev_name, O_RDONLY);
+       else {
+               for (p=fls; *p; ++p) {
+                       rtc_dev_fd = open(*p, O_RDONLY);
+
+                       if (rtc_dev_fd < 0 && (errno == ENOENT || errno == ENODEV))
+                               continue;
+                       rtc_dev_name = *p;
+                       break;
+               }
+               if (rtc_dev_fd < 0)
+                       rtc_dev_name = *fls;    /* default for error messages */
        }
-       rtc_dev_name = *fls;    /* default */
-       return -1;
+
+       if (rtc_dev_fd != 1)
+               atexit(close_rtc);
+       return rtc_dev_fd;
 }
 
 static int
@@ -219,7 +236,7 @@ synchronize_to_clock_tick_rtc(void) {
 int rtc_fd;  /* File descriptor of /dev/rtc */
 int ret;
 
-  rtc_fd = open(rtc_dev_name, O_RDONLY);
+  rtc_fd = open_rtc();
   if (rtc_fd == -1) {
     outsyserr(_("open() of %s failed"), rtc_dev_name);
     ret = 1;
@@ -287,7 +304,6 @@ int ret;
                "failed unexpectedly"), rtc_dev_name);
       ret = 1;
     }
-    close(rtc_fd);
   }
   return ret;
 }
@@ -302,7 +318,6 @@ read_hardware_clock_rtc(struct tm *tm) {
        /* Read the RTC time/date, return answer via tm */
        rc = do_rtc_read_ioctl(rtc_fd, tm);
 
-       close(rtc_fd);
        return rc;
 }
 
@@ -350,7 +365,6 @@ set_hardware_clock_rtc(const struct tm *new_broken_time) {
        if (debug)
                printf(_("ioctl(%s) was successful.\n"), ioctlname);
 
-       close(rtc_fd);
        return 0;
 }
 
@@ -372,10 +386,8 @@ static struct clock_ops rtc = {
 struct clock_ops *
 probe_for_rtc_clock(){
        int rtc_fd = open_rtc();
-       if (rtc_fd >= 0) {
-               close(rtc_fd);
+       if (rtc_fd >= 0)
                return &rtc;
-       }
        if (debug)
                outsyserr(_("Open of %s failed"), rtc_dev_name);
        return NULL;
@@ -408,7 +420,6 @@ get_epoch_rtc(unsigned long *epoch_p, int silent) {
   if (ioctl(rtc_fd, RTC_EPOCH_READ, epoch_p) == -1) {
     if (!silent)
       outsyserr(_("ioctl(RTC_EPOCH_READ) to %s failed"), rtc_dev_name);
-    close(rtc_fd);
     return 1;
   }
 
@@ -416,7 +427,6 @@ get_epoch_rtc(unsigned long *epoch_p, int silent) {
          printf(_("we have read epoch %ld from %s "
                 "with RTC_EPOCH_READ ioctl.\n"), *epoch_p, rtc_dev_name);
 
-  close(rtc_fd);
   return 0;
 }
 
@@ -460,10 +470,8 @@ set_epoch_rtc(unsigned long epoch) {
              "does not have the RTC_EPOCH_SET ioctl.\n"), rtc_dev_name);
     else
       outsyserr(_("ioctl(RTC_EPOCH_SET) to %s failed"), rtc_dev_name);
-    close(rtc_fd);
     return 1;
   }
 
-  close(rtc_fd);
   return 0;
 }