Martin Schwidefsky 4be77398ac time: Fix 1ns/tick drift w/ GENERIC_TIME_VSYSCALL_OLD ... Since commit 1e75fa8be9 (time: Condense timekeeper.xtime into xtime_sec - merged in v3.6), there has been an problem with the error accounting in the timekeeping code, such that when truncating to nanoseconds, we round up to the next nsec, but the balancing adjustment to the ntp_error value was dropped. This causes 1ns per tick drift forward of the clock. In 3.7, this logic was isolated to only GENERIC_TIME_VSYSCALL_OLD architectures (s390, ia64, powerpc). The fix is simply to balance the accounting and to subtract the added nanosecond from ntp_error. This allows the internal long-term clock steering to keep the clock accurate. While this fix removes the regression added in 1e75fa8be9, the ideal solution is to move away from GENERIC_TIME_VSYSCALL_OLD and use the new VSYSCALL method, which avoids entirely the nanosecond granular rounding, and the resulting short-term clock adjustment oscillation needed to keep long term accurate time. [ jstultz: Many thanks to Martin for his efforts identifying this subtle bug, and providing the fix. ] Originally-from: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Paul Turner <pjt@google.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable <stable@vger.kernel.org> #v3.6+ Link: http://lkml.kernel.org/r/1385149491-20307-1-git-send-email-john.stultz@linaro.org Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2013-11-22 21:08:11 +01:00
..
alarmtimer.c	alarmtimer: return EINVAL instead of ENOTSUPP if rtcdev doesn't exist	2013-10-18 16:23:58 -07:00
clockevents.c	Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-11-12 10:36:00 +09:00
clocksource.c	time: Fix signedness bug in sysfs_get_uname() and its callers	2013-10-18 16:45:58 -07:00
jiffies.c
Kconfig	nohz: Drop generic vtime obsolete dependency on CONFIG_64BIT	2013-09-30 15:37:01 +02:00
Makefile	sched_clock: Make ARM's sched_clock generic for all architectures	2013-06-12 14:02:13 -07:00
ntp.c	Linux 3.12-rc3	2013-10-03 07:52:21 +02:00
ntp_internal.h	ntp: Rework do_adjtimex to take timespec and tai arguments	2013-04-04 13:18:15 -07:00
posix-clock.c
sched_clock.c	sched_clock: Remove sched_clock_func() hook	2013-10-09 16:54:39 -07:00
tick-broadcast.c	tick: broadcast: Deny per-cpu clockevents from being broadcast sources	2013-10-02 11:34:06 +02:00
tick-common.c	tick: Document tick_do_timer_cpu	2013-11-19 14:59:50 +01:00
tick-internal.h	time: Fix signedness bug in sysfs_get_uname() and its callers	2013-10-18 16:45:58 -07:00
tick-oneshot.c
tick-sched.c	NOHZ: Check for nohz active instead of nohz enabled	2013-11-19 14:59:50 +01:00
timeconv.c
timekeeping.c	time: Fix 1ns/tick drift w/ GENERIC_TIME_VSYSCALL_OLD	2013-11-22 21:08:11 +01:00
timekeeping_debug.c	power: Add option to log time spent in suspend	2013-05-29 12:57:34 -07:00
timekeeping_internal.h	power: Add option to log time spent in suspend	2013-05-29 12:57:34 -07:00
timer_list.c	timer_list: correct the iterator for timer_list	2013-08-28 19:26:38 -07:00
timer_stats.c	timer stats: Add a 'Collection: active/inactive' line to timer usage statistics	2013-10-10 09:59:25 +02:00