From: David P. Reed Date: Wed, 14 Nov 2007 22:49:21 +0000 (-0500) Subject: ntp: fix typo that makes sync_cmos_clock erratic X-Git-Tag: firefly_0821_release~24281^2~7 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fa6a1a554b50cbb7763f6907e6fef927ead480d9;p=firefly-linux-kernel-4.4.55.git ntp: fix typo that makes sync_cmos_clock erratic 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: Thomas Gleixner --- diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index de6a2d6b3ebb..14a2ecf2b318 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -205,7 +205,7 @@ static void sync_cmos_clock(unsigned long dummy) return; getnstimeofday(&now); - if (abs(xtime.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) + if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) fail = update_persistent_clock(now); next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec;