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linux/kernel/time
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Jason Wessel deda2e8196 timekeeping: Fix overflow in rawtime tv_nsec on 32 bit archs 
The tv_nsec is a long and when added to the shifted interval it can wrap
and become negative which later causes looping problems in the
getrawmonotonic().  The edge case occurs when the system has slept for
a short period of time of ~2 seconds.

A trace printk of the values in this patch illustrate the problem:

ftrace time stamp: log
43.716079: logarithmic_accumulation: raw: 3d0913 tv_nsec d687faa
43.718513: logarithmic_accumulation: raw: 3d0913 tv_nsec da588bd
43.722161: logarithmic_accumulation: raw: 3d0913 tv_nsec de291d0
46.349925: logarithmic_accumulation: raw: 7a122600 tv_nsec e1f9ae3
46.349930: logarithmic_accumulation: raw: 1e848980 tv_nsec 8831c0e3

The kernel starts looping at 46.349925 in the getrawmonotonic() due to
the negative value from adding the raw value to tv_nsec.

A simple solution is to accumulate into a u64, and then normalize it
to a timespec_t.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
 [ Reworked variable names and simplified some of the code. - John ]
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-08-12 09:53:39 -07:00
..
clockevents.c clockevent: Don't remove broadcast device when cpu is dead 2010-01-18 14:44:50 +01:00
clocksource.c clocksource: Add __clocksource_updatefreq_hz/khz methods 2010-07-27 12:40:55 +02:00
jiffies.c clocksource: Cleanup clocksource selection 2009-08-15 10:55:46 +02:00
Kconfig time: Kill off CONFIG_GENERIC_TIME 2010-07-27 12:40:54 +02:00
Makefile time: add function to convert between calendar time and broken-down time for universal use 2009-09-24 07:20:56 -07:00
ntp.c ntp: Make time_adjust static 2010-03-23 17:19:37 +01:00
tick-broadcast.c fix comment/printk typos concerning "already" 2010-07-11 21:45:40 +02:00
tick-common.c clockevents: Convert to raw_spinlock 2009-12-14 23:55:34 +01:00
tick-internal.h clockevents: Make tick_device_lock static 2009-12-14 23:55:34 +01:00
tick-oneshot.c clockevents: Sanitize min_delta_ns adjustment and prevent overflows 2010-03-12 19:10:29 +01:00
tick-sched.c Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-08-06 13:12:36 -07:00
timecompare.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
timeconv.c time: add function to convert between calendar time and broken-down time for universal use 2009-09-24 07:20:56 -07:00
timekeeping.c timekeeping: Fix overflow in rawtime tv_nsec on 32 bit archs 2010-08-12 09:53:39 -07:00
timer_list.c sched: Intoduce get_cpu_iowait_time_us() 2010-05-09 19:35:27 +02:00
timer_stats.c hrtimers: Convert to raw_spinlocks 2009-12-14 23:55:34 +01:00