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6a669ee8a7
linux/kernel
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Thomas Gleixner 6a669ee8a7 timekeeping: Prevent time going backwards on resume 
Timekeeping resume adjusts xtime by adding the slept time in seconds and
resets the reference value of the clock source (clock->cycle_last).
clock->cycle last is used to calculate the delta between the last xtime
update and the readout of the clock source in __get_nsec_offset(). xtime
plus the offset is the current time. The resume code ignores the delta
which had already elapsed between the last xtime update and the actual
time of suspend. If the suspend time is short, then we can see time
going backwards on resume.

Suspend:
offs_s = clock->read() - clock->cycle_last;
now = xtime + offs_s;
timekeeping_suspend_time = read_rtc();

Resume:
sleep_time = read_rtc() - timekeeping_suspend_time;
xtime.tv_sec += sleep_time;
clock->cycle_last = clock->read();
offs_r = clock->read() - clock->cycle_last;
now = xtime + offs_r;

if sleep_time_seconds == 0 and offs_r < offs_s, then time goes
backwards.

Fix this by storing the offset from the last xtime update and add it to
xtime during resume, when we reset clock->cycle_last:

sleep_time = read_rtc() - timekeeping_suspend_time;
xtime.tv_sec += sleep_time;
xtime += offs_s;	/* Fixup xtime offset at suspend time */
clock->cycle_last = clock->read();
offs_r = clock->read() - clock->cycle_last;
now = xtime + offs_r;

Thanks to Marcelo for tracking this down on the OLPC and providing the
necessary details to analyze the root cause.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Tosatti <marcelo@kvack.org>
2007-09-16 15:36:43 +02:00
..
irq request_irq: fix DEBUG_SHIRQ handling 2007-08-31 01:42:23 -07:00
power PM: Fix dependencies of CONFIG_SUSPEND and CONFIG_HIBERNATION 2007-08-31 01:42:22 -07:00
time timekeeping: Prevent time going backwards on resume 2007-09-16 15:36:43 +02:00
.gitignore
acct.c Cleanup non-arch xtime uses, use get_seconds() or current_kernel_time(). 2007-07-25 10:09:20 -07:00
audit.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
audit.h Audit: add TTY input auditing 2007-07-16 09:05:47 -07:00
auditfilter.c [PATCH] allow audit filtering on bit & operations 2007-07-22 09:57:02 -04:00
auditsc.c kernel/auditsc.c: fix an off-by-one 2007-08-22 19:52:44 -07:00
capability.c [PATCH] pid: replace do/while_each_task_pid with do/while_each_pid_task 2007-02-12 09:48:32 -08:00
compat.c signal/timer/event: timerfd compat code 2007-05-11 08:29:36 -07:00
configs.c use simple_read_from_buffer in kernel/ 2007-05-09 12:30:49 -07:00
cpu.c PM: Fix dependencies of CONFIG_SUSPEND and CONFIG_HIBERNATION 2007-08-31 01:42:22 -07:00
cpuset.c usermodehelper: Tidy up waiting 2007-07-18 08:47:40 -07:00
delayacct.c sched: update delay-accounting to use CFS's precise stats 2007-07-09 18:52:00 +02:00
die_notifier.c move die notifier handling to common code 2007-05-08 11:15:04 -07:00
dma.c [PATCH] struct seq_operations and struct file_operations constification 2006-12-07 08:39:46 -08:00
exec_domain.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
exit.c Assign task_struct.exit_code before taskstats_exit() 2007-08-31 01:42:22 -07:00
extable.c [PATCH] symbol_put_addr() locks kernel 2006-05-15 11:20:55 -07:00
fork.c mm: Remove slab destructors from kmem_cache_create(). 2007-07-20 10:11:58 +09:00
futex_compat.c futex_compat: fix list traversal bugs 2007-09-11 17:21:20 -07:00
futex.c futex_unlock_pi() hurts my brain and may cause application deadlock 2007-08-22 19:52:44 -07:00
hrtimer.c Cache xtime every call to update_wall_time 2007-07-25 10:17:44 -07:00
itimer.c The scheduled -EINVAL for invalid timevals in setitimer 2007-05-08 11:15:13 -07:00
kallsyms.c kallsyms: make KSYM_NAME_LEN include space for trailing '\0' 2007-07-17 10:23:03 -07:00
Kconfig.hz [PATCH] HZ: 300Hz support 2006-12-07 08:39:36 -08:00
Kconfig.preempt [PATCH] sched: arch preempt notifier mechanism 2007-07-26 13:40:43 +02:00
kexec.c kdump/kexec: calculate note size at compile time 2007-05-08 11:15:07 -07:00
kfifo.c is_power_of_2: kernel/kfifo.c 2007-07-16 09:05:50 -07:00
kmod.c Restore call_usermodehelper_pipe() behaviour 2007-09-11 17:21:20 -07:00
kprobes.c fix compilation with gcc 4.2 2007-08-11 15:47:42 -07:00
ksysfs.c FRV: Fix linkage problems 2007-07-20 12:01:34 -07:00
kthread.c kthread: silence bogus section mismatch warning 2007-07-31 15:39:42 -07:00
latency.c [PATCH] severing module.h->sched.h 2006-12-04 02:00:22 -05:00
lockdep_internals.h [PATCH] lockdep: more chains 2006-12-07 08:39:43 -08:00
lockdep_proc.c Fix leak on /proc/lockdep_stats 2007-07-31 15:39:40 -07:00
lockdep.c lockdep debugging: give stacktrace for init_error 2007-07-19 10:04:49 -07:00
Makefile user namespace: add the framework 2007-07-16 09:05:47 -07:00
module.c Fix Off-by-one in /sys/module/*/refcnt 2007-08-22 14:35:35 -07:00
mutex-debug.c [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
mutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
mutex.c lockstat: measure lock bouncing 2007-07-19 10:04:49 -07:00
mutex.h [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
nsproxy.c mm: Remove slab destructors from kmem_cache_create(). 2007-07-20 10:11:58 +09:00
panic.c Report that kernel is tainted if there was an OOPS 2007-07-17 10:23:02 -07:00
params.c modules: better error messages when modules fail to load due to a sysfs problem. 2007-07-30 14:25:23 -07:00
pid.c namespace: ensure clone_flags are always stored in an unsigned long 2007-07-16 09:05:48 -07:00
posix-cpu-timers.c sched: make posix-cpu-timers use CFS's accounting information 2007-07-09 18:51:58 +02:00
posix-timers.c posix-timers: fix creation race 2007-08-22 19:52:46 -07:00
printk.c fix - ensure we don't use bootconsoles after init has been released 2007-08-21 20:23:53 -07:00
profile.c fix compilation with gcc 4.2 2007-08-11 15:47:42 -07:00
ptrace.c Fix spurious syscall tracing after PTRACE_DETACH + PTRACE_ATTACH 2007-09-10 18:57:47 -07:00
rcupdate.c Add suspend-related notifications for CPU hotplug 2007-05-09 12:30:56 -07:00
rcutorture.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
relay.c Fix a use after free bug in kernel->userspace relay file support 2007-07-31 15:39:42 -07:00
resource.c libata/IDE: remove combined mode quirk 2007-04-28 14:15:59 -04:00
rtmutex_common.h FUTEX: Tidy up the code 2007-07-16 09:05:49 -07:00
rtmutex-debug.c FUTEX: Tidy up the code 2007-07-16 09:05:49 -07:00
rtmutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex-tester.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
rtmutex.c FUTEX: Tidy up the code 2007-07-16 09:05:49 -07:00
rtmutex.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rwsem.c lockstat: hook into spinlock_t, rwlock_t, rwsem and mutex 2007-07-19 10:04:49 -07:00
sched_debug.c sched: debug: fix sum_exec_runtime clearing 2007-09-05 14:32:49 +02:00
sched_fair.c sched: fix ideal_runtime calculations for reniced tasks 2007-09-05 14:32:49 +02:00
sched_idletask.c sched: remove the 'u64 now' parameter from ->put_prev_task() 2007-08-09 11:16:49 +02:00
sched_rt.c sched: optimize task_tick_rt() a bit 2007-08-24 20:39:10 +02:00
sched_stats.h [PATCH] sched: add schedstat_set() API 2007-08-02 17:41:40 +02:00
sched.c sched: fix xtensa build warning 2007-09-05 14:32:49 +02:00
seccomp.c make seccomp zerocost in schedule 2007-07-16 09:05:50 -07:00
signal.c sigqueue_free: fix the race with collect_signal() 2007-08-31 01:42:23 -07:00
softirq.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
softlockup.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
spinlock.c lockstat: hook into spinlock_t, rwlock_t, rwsem and mutex 2007-07-19 10:04:49 -07:00
srcu.c [PATCH] SRCU: report out-of-memory errors 2006-10-04 07:55:30 -07:00
stacktrace.c [PATCH] lockdep: stacktrace subsystem, core 2006-07-03 15:27:02 -07:00
stop_machine.c Fix stop_machine_run problem with naughty real time process 2007-07-16 09:05:41 -07:00
sys_ni.c diskquota: 32bit quota tools on 64bit architectures 2007-07-16 09:05:48 -07:00
sys.c setpgid(child) fails if the child was forked by sub-thread 2007-08-31 01:42:22 -07:00
sysctl.c sched: cleanup, sched_granularity -> sched_min_granularity 2007-08-25 18:41:53 +02:00
taskstats.c taskstats: add context-switch counters 2007-07-16 09:05:46 -07:00
time.c Cleanup non-arch xtime uses, use get_seconds() or current_kernel_time(). 2007-07-25 10:09:20 -07:00
timer.c Pull ia64-clocksource into release branch 2007-07-20 11:26:47 -07:00
tsacct.c Cleanup non-arch xtime uses, use get_seconds() or current_kernel_time(). 2007-07-25 10:09:20 -07:00
uid16.c header cleaning: don't include smp_lock.h when not used 2007-05-08 11:15:07 -07:00
user_namespace.c userns: don't leak root user 2007-08-31 01:42:23 -07:00
user.c mm: Remove slab destructors from kmem_cache_create(). 2007-07-20 10:11:58 +09:00
utsname_sysctl.c remove CONFIG_UTS_NS and CONFIG_IPC_NS 2007-07-16 09:05:47 -07:00
utsname.c namespace: ensure clone_flags are always stored in an unsigned long 2007-07-16 09:05:48 -07:00
wait.c Fix occurrences of "the the " 2007-05-09 08:57:56 +02:00
workqueue.c fix bogus hotplug cpu warning 2007-08-27 10:27:48 -07:00