Re: hwclock "hanging" for ~24 hours

[Karel Zak <kzak@xxxxxxxxxx>]

On Tue, Aug 12, 2008 at 02:22:47PM +0200, Karel Zak wrote:
> 
> On Sat, Aug 09, 2008 at 05:05:23PM +0200, Tomasz Chmielewski wrote:
> > Karel Zak schrieb:
> >
> > (...)
> >
> >>> But would it solve the issue, really?
> >>
> >>  Yes, that's core of the problem. But we also need to remove some return
> >>  code checks from manipulate_clock(). These checks are unnecessary,
> >>  because there is hclock_valid boolean... (this is my bug.)
> >>
> >>> hwclock from busybox is able to show the clock (Tue Nov 30 00:00:00
> >>> 1999  0.000000) and also set it; the above seems to exit only - and
> >>> still, we're not able to show or set the clock?
> >>
> >>  I'll send a patch ASAP.
> >
> > Could you notify the list when the patch is ready, please?
> 
>  The patch is below. It's based on gettimeofday() rather than on
>  SIGALRM (alarm(2)). The gettimeofday has some overhead, but it
>  shouldn't be a big problem for the synchronization function (... and
>  it's fallback for systems without RTC_UIE_ON).
> 
>  Please, test & review. I'd like to use the patch in 2.14.1.

 sorry, the patch:



>From 50506d3535f4af36a550dcd91136224a608e61f7 Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@xxxxxxxxxx>
Date: Tue, 12 Aug 2008 13:58:51 +0200
Subject: [PATCH] hwclock: use time limit for synchronization busy wait

Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
---
 hwclock/clock.h   |    1 +
 hwclock/hwclock.c |    2 +-
 hwclock/rtc.c     |   23 ++++++++++++-----------
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/hwclock/clock.h b/hwclock/clock.h
index 6e8a9b4..cbdf999 100644
--- a/hwclock/clock.h
+++ b/hwclock/clock.h
@@ -33,6 +33,7 @@ extern void outsyserr(char *msg, ...)
 #else
         ;
 #endif
+extern double time_diff(struct timeval subtrahend, struct timeval subtractor);
 /* cmos.c */
 extern void set_cmos_epoch(int ARCconsole, int SRM);
 extern void set_cmos_access(int Jensen, int funky_toy);
diff --git a/hwclock/hwclock.c b/hwclock/hwclock.c
index 12e7676..44f648c 100644
--- a/hwclock/hwclock.c
+++ b/hwclock/hwclock.c
@@ -182,7 +182,7 @@ read_date_from_file (struct tm *tm) {
   write_date_to_file (tm);
 }
 
-static double
+double
 time_diff(struct timeval subtrahend, struct timeval subtractor) {
 /*---------------------------------------------------------------------------
   The difference in seconds between two times in "timeval" format.
diff --git a/hwclock/rtc.c b/hwclock/rtc.c
index 3eb1f4e..e59414f 100644
--- a/hwclock/rtc.c
+++ b/hwclock/rtc.c
@@ -179,8 +179,8 @@ busywait_for_rtc_clock_tick(const int rtc_fd) {
   struct tm start_time;
     /* The time when we were called (and started waiting) */
   struct tm nowtime;
-  int i;  /* local loop index */
   int rc;
+  struct timeval begin, now;
 
   if (debug)
     printf(_("Waiting in loop for time from %s to change\n"),
@@ -191,25 +191,26 @@ busywait_for_rtc_clock_tick(const int rtc_fd) {
     return 1;
 
   /* Wait for change.  Should be within a second, but in case something
-     weird happens, we have a limit on this loop to reduce the impact
-     of this failure.
-     */
-  for (i = 0;
-       (rc = do_rtc_read_ioctl(rtc_fd, &nowtime)) == 0
-        && start_time.tm_sec == nowtime.tm_sec;
-       i++)
-    if (i >= 1000000) {
+   * weird happens, we have a time limit (1.5s) on this loop to reduce the
+   * impact of this failure.
+   */
+  gettimeofday(&begin, NULL);
+  do {
+    rc = do_rtc_read_ioctl(rtc_fd, &nowtime);
+    if (rc || start_time.tm_sec != nowtime.tm_sec)
+      break;
+    gettimeofday(&now, NULL);
+    if (time_diff(now, begin) > 1.5) {
       fprintf(stderr, _("Timed out waiting for time change.\n"));
       return 2;
     }
+  } while(1);
 
   if (rc)
     return 3;
   return 0;
 }
 
-
-
 static int
 synchronize_to_clock_tick_rtc(void) {
 /*----------------------------------------------------------------------------
-- 
1.5.5.1


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