Changeset 3621 in MondoRescue for branches/3.3/mindi-busybox/libbb/rtc.c

Timestamp:

Dec 20, 2016, 4:07:32 PM (7 years ago)

Author:

Bruno Cornec

Message:

New 3?3 banch for incorporation of latest busybox 1.25. Changing minor version to handle potential incompatibilities.

Location:

branches/3.3

Files:

• . (copied) (copied from branches/3.2 )
• mindi-busybox/libbb/rtc.c (modified) (2 diffs)

branches/3.3/mindi-busybox/libbb/rtc.c

@@ -23 +23 @@
 
         while (fgets(buffer, sizeof(buffer), f)) {
-            if (strncmp(buffer, "UTC", 3) == 0) {
+            if (is_prefixed_with(buffer, "UTC")) {
                 utc = 1;
                 break;
@@ -34 +34 @@
 }
 
+/* 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 (!*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/rtc0";
-        rtc = open(*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);
 }