• David P. Reed's avatar
    ntp: fix typo that makes sync_cmos_clock erratic · fa6a1a55
    David P. Reed authored
    Fix a typo in ntp.c that has caused updating of the persistent (RTC)
    clock when synced to NTP to behave erratically.
    
    When debugging a freeze that arises on my AMD64 machines when I
    run the ntpd service, I added a number of printk's to monitor the
    sync_cmos_clock procedure.  I discovered that it was not syncing to
    cmos RTC every 11 minutes as documented, but instead would keep trying
    every second for hours at a time.  The reason turned out to be a typo
    in sync_cmos_clock, where it attempts to ensure that
    update_persistent_clock is called very close to 500 msec. after a 1
    second boundary (required by the PC RTC's spec). That typo referred to
    "xtime" in one spot, rather than "now", which is derived from "xtime"
    but not equal to it.  This makes the test erratic, creating a
    "coin-flip" that decides when update_persistent_clock is called - when
    it is called, which is rarely, it may be at any time during the one
    second period, rather than close to 500 msec, so the value written is
    needlessly incorrect, too.
    
    Signed-off-by: David P. Reed
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    fa6a1a55
ntp.c 11.4 KB