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John Stultz cb33217b1b time: Avoid accumulating time drift in suspend/resume 
Because the read_persistent_clock interface is usually backed by
only a second granular interface, each time we read from the persistent
clock for suspend/resume, we introduce a half second (on average) of error.

In order to avoid this error accumulating as the system is suspended
over and over, this patch measures the time delta between the persistent
clock and the system CLOCK_REALTIME.

If the delta is less then 2 seconds from the last suspend, we compensate
by using the previous time delta (keeping it close). If it is larger
then 2 seconds, we assume the clock was set or has been changed, so we
do no correction and update the delta.

Note: If NTP is running, ths could seem to "fight" with the NTP corrected
time, where as if the system time was off by 1 second, and NTP slewed the
value in, a suspend/resume cycle could undo this correction, by trying to
restore the previous offset from the persistent clock.  However, without
this patch, since each read could cause almost a full second worth of
error, its possible to get almost 2 seconds of error just from the
suspend/resume cycle alone, so this about equal to any offset added by
the compensation.

Further on systems that suspend/resume frequently, this should keep time
closer then NTP could compensate for if the errors were allowed to
accumulate.

Credits to Arve Hjønnevåg for suggesting this solution.

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-06-21 16:55:37 -07:00
..
debug Fix common misspellings 2011-03-31 11:26:23 -03:00
events Merge branch 'perf/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent 2011-06-04 12:13:06 +02:00
gcov gcov: disable CONFIG_CONSTRUCTORS when not needed by CONFIG_GCOV_KERNEL 2011-06-15 20:04:01 -07:00
irq genirq: Prevent potential NULL dereference in irq_set_irq_wake() 2011-06-10 10:53:42 +02:00
power PM / Hibernate: Update kerneldoc comments in hibernate.c 2011-05-24 23:36:06 +02:00
time time: Avoid accumulating time drift in suspend/resume 2011-06-21 16:55:37 -07:00
trace tracing: Fix regression in printk_formats file 2011-06-09 08:42:15 -04:00
.gitignore
acct.c
async.c
audit.c netlink: kill loginuid/sessionid/sid members from struct netlink_skb_parms 2011-03-03 10:55:40 -08:00
audit.h audit: make functions static 2010-10-30 01:42:19 -04:00
audit_tree.c Fix common misspellings 2011-03-31 11:26:23 -03:00
audit_watch.c kill path_lookup() 2011-03-14 09:15:23 -04:00
auditfilter.c netlink: kill loginuid/sessionid/sid members from struct netlink_skb_parms 2011-03-03 10:55:40 -08:00
auditsc.c audit: acquire creds selectively to reduce atomic op overhead 2011-04-27 15:11:03 +02:00
backtracetest.c
bounds.c memcg: remove direct page_cgroup-to-page pointer 2011-03-23 19:46:28 -07:00
capability.c Merge branch 'master' into next 2011-05-19 18:51:57 +10:00
cgroup.c cgroup: remove the ns_cgroup 2011-05-26 17:12:34 -07:00
cgroup_freezer.c cgroups: add per-thread subsystem callbacks 2011-05-26 17:12:34 -07:00
compat.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2011-05-25 15:35:32 -07:00
configs.c llseek: automatically add .llseek fop 2010-10-15 15:53:27 +02:00
cpu.c Fix common misspellings 2011-03-31 11:26:23 -03:00
cpuset.c cpuset: Fix cpuset_cpus_allowed_fallback(), don't update tsk->rt.nr_cpus_allowed 2011-05-28 17:02:57 +02:00
crash_dump.c crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn 2011-03-23 19:47:19 -07:00
cred.c Merge branch 'docs-move' of git://git.kernel.org/pub/scm/linux/kernel/git/rdunlap/linux-docs 2011-05-27 10:25:02 -07:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c memcg: clear mm->owner when last possible owner leaves 2011-06-15 20:04:01 -07:00
extable.c extable, core_kernel_data(): Make sure all archs define _sdata 2011-05-20 08:56:56 +02:00
fork.c mm: Fix boot crash in mm_alloc() 2011-05-29 11:32:28 -07:00
freezer.c Freezer: Use SMP barriers 2011-05-17 23:19:17 +02:00
futex.c futex: Set FLAGS_HAS_TIMEOUT during futex_wait restart setup 2011-04-15 16:34:32 +02:00
futex_compat.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
groups.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
hrtimer.c hrtimers: Fix typo causing erratic timers 2011-05-25 15:31:58 -07:00
hung_task.c watchdog, hung_task_timeout: Add Kconfig configurable default 2011-04-28 09:13:17 +02:00
irq_work.c irq_work: Use per cpu atomics instead of regular atomics 2010-12-18 15:54:48 +01:00
itimer.c
jump_label.c jump_label: Check entries limit in __jump_label_update 2011-05-25 19:56:36 -04:00
kallsyms.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-25 17:52:22 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks arch:Kconfig.locks Remove unused config option. 2011-04-10 17:01:05 +02:00
Kconfig.preempt
kexec.c PM: Remove sysdev suspend, resume and shutdown operations 2011-05-11 21:37:15 +02:00
kfifo.c kfifo: fix scatterlist usage 2010-10-01 10:50:58 -07:00
kmod.c KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring 2011-06-17 09:40:48 -07:00
kprobes.c Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2011-01-07 17:02:58 -08:00
ksysfs.c kernel/ksysfs.c: expose file_caps_enabled in sysfs 2011-04-19 16:45:51 -07:00
kthread.c cpuset: Fix cpuset_cpus_allowed_fallback(), don't update tsk->rt.nr_cpus_allowed 2011-05-28 17:02:57 +02:00
latencytop.c Fix common misspellings 2011-03-31 11:26:23 -03:00
lockdep.c lockdep: Fix lock_is_held() on recursion 2011-06-07 12:25:50 +02:00
lockdep_internals.h
lockdep_proc.c lockdep: Remove unused 'factor' variable from lockdep_stats_show() 2011-03-23 13:54:47 +01:00
lockdep_states.h
Makefile cgroup: remove the ns_cgroup 2011-05-26 17:12:34 -07:00
module.c Merge branch 'staging-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6 2011-05-23 12:49:28 -07:00
mutex-debug.c mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
mutex-debug.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
mutex.c lockdep, mutex: provide mutex_lock_nest_lock 2011-05-25 08:39:17 -07:00
mutex.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
notifier.c
nsproxy.c cgroup: remove the ns_cgroup 2011-05-26 17:12:34 -07:00
padata.c Fix common misspellings 2011-03-31 11:26:23 -03:00
panic.c move x86 specific oops=panic to generic code 2011-03-22 17:44:11 -07:00
params.c params.c: Use new strtobool function to process boolean inputs 2011-05-19 16:55:28 +09:30
pid.c next_pidmap: fix overflow condition 2011-04-18 10:35:30 -07:00
pid_namespace.c pidns: call pid_ns_prepare_proc() from create_pid_namespace() 2011-03-23 19:46:58 -07:00
pm_qos_params.c Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6 2011-05-29 11:18:09 -07:00
posix-cpu-timers.c hrtimers: Avoid touching inactive timer bases 2011-05-23 13:59:54 +02:00
posix-timers.c posix-timers: RCU conversion 2011-05-24 12:10:51 +02:00
printk.c printk: allocate kernel log buffer earlier 2011-05-25 08:39:48 -07:00
profile.c kernel/profile.c: remove some duplicate code from profile_hits() 2011-05-26 17:12:37 -07:00
ptrace.c ptrace: ptrace_resume() shouldn't wake up !TASK_TRACED thread 2011-05-25 19:20:21 +02:00
range.c kernel/range.c: fix clean_sort_range() for the case of full array 2010-11-12 07:55:31 -08:00
rcupdate.c rcu: Use WARN_ON_ONCE for DEBUG_OBJECTS_RCU_HEAD warnings 2011-05-05 23:16:57 -07:00
rcutiny.c sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00
rcutiny_plugin.h rcu: Converge TINY_RCU expedited and normal boosting 2011-05-05 23:16:58 -07:00
rcutorture.c rcu: mark rcutorture boosting callback as being on-stack 2011-05-05 23:16:57 -07:00
rcutree.c rcu: Move RCU_BOOST #ifdefs to header file 2011-06-16 16:12:05 -07:00
rcutree.h rcu: Move RCU_BOOST #ifdefs to header file 2011-06-16 16:12:05 -07:00
rcutree_plugin.h rcu: Move RCU_BOOST #ifdefs to header file 2011-06-16 16:12:05 -07:00
rcutree_trace.c rcu: use softirq instead of kthreads except when RCU_BOOST=y 2011-06-15 23:07:21 -07:00
relay.c Clean up relay_alloc_page_array() slightly by using vzalloc rather than vmalloc and memset 2010-11-05 08:21:34 -07:00
res_counter.c memcg: res_counter_read_u64(): fix potential races on 32-bit machines 2011-03-23 19:46:22 -07:00
resource.c resources: add arch hook for preventing allocation in reserved areas 2010-12-17 10:01:09 -08:00
rtmutex-debug.c rtmutex: Simplify PI algorithm and make highest prio task get lock 2011-01-27 21:13:51 -05:00
rtmutex-debug.h
rtmutex-tester.c rtmutex: tester: Remove the remaining BKL leftovers 2011-02-22 22:07:22 +01:00
rtmutex.c rtmutex: Simplify PI algorithm and make highest prio task get lock 2011-01-27 21:13:51 -05:00
rtmutex.h
rtmutex_common.h rtmutex: Simplify PI algorithm and make highest prio task get lock 2011-01-27 21:13:51 -05:00
rwsem.c
sched.c sched: Fix/clarify set_task_cpu() locking rules 2011-06-07 12:26:40 +02:00
sched_autogroup.c Fix common misspellings 2011-03-31 11:26:23 -03:00
sched_autogroup.h sched, autogroup: Stop going ahead if autogroup is disabled 2011-02-23 11:33:59 +01:00
sched_clock.c sched: Add some clock info to sched_debug 2010-11-23 10:29:08 +01:00
sched_cpupri.c
sched_cpupri.h
sched_debug.c sched: Get rid of lock_depth 2011-04-24 13:18:38 +02:00
sched_fair.c sched: Fix ->min_vruntime calculation in dequeue_entity() 2011-05-28 17:02:56 +02:00
sched_features.h sched: Move the second half of ttwu() to the remote cpu 2011-04-14 08:52:41 +02:00
sched_idletask.c sched: Drop the rq argument to sched_class::select_task_rq() 2011-04-14 08:52:36 +02:00
sched_rt.c sched: Check if lowest_mask is initialized in find_lowest_rq() 2011-06-15 11:44:48 +02:00
sched_stats.h sched: More sched_domain iterations fixes 2011-05-28 17:02:54 +02:00
sched_stoptask.c sched: Drop the rq argument to sched_class::select_task_rq() 2011-04-14 08:52:36 +02:00
seccomp.c
semaphore.c
signal.c signal.c: fix kernel-doc notation 2011-06-14 19:12:17 -07:00
smp.c generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts 2011-06-17 10:17:12 +02:00
softirq.c rcu: Use softirq to address performance regression 2011-06-14 15:25:39 -07:00
spinlock.c
srcu.c rcu: demote SRCU_SYNCHRONIZE_DELAY from kernel-parameter status 2011-01-14 04:56:49 -08:00
stacktrace.c
stop_machine.c kthread: use kthread_create_on_node() 2011-03-22 17:44:01 -07:00
sys.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6 2011-05-19 18:24:11 -07:00
sys_ni.c ipc: Add missing sys_ni entries for ipc/compat.c functions 2011-05-20 13:53:02 -07:00
sysctl.c perf: Comment /proc/sys/kernel/perf_event_paranoid to be part of user ABI 2011-06-04 12:22:04 +02:00
sysctl_binary.c open-style analog of vfs_path_lookup() 2011-03-14 09:15:28 -04:00
sysctl_check.c sysctl_check: drop dead code 2011-03-23 19:46:51 -07:00
taskstats.c taskstats: use appropriate printk priority level 2011-03-23 19:47:14 -07:00
test_kprobes.c kprobes: Fix selftest to clear flags field for reusing probes 2010-10-14 08:55:27 +02:00
time.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-15 18:53:35 -07:00
timeconst.pl
timer.c timers: Consider slack value in mod_timer() 2011-06-03 15:02:32 +02:00
tracepoint.c jump label: Introduce static_branch() interface 2011-04-04 12:48:08 -04:00
tsacct.c taskstats: use real microsecond granularity for CPU times 2010-10-27 18:03:17 -07:00
uid16.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
up.c
user-return-notifier.c Fix common misspellings 2011-03-31 11:26:23 -03:00
user.c userns: add a user_namespace as creator/owner of uts_namespace 2011-03-23 19:46:59 -07:00
user_namespace.c user_ns: improve the user_ns on-the-slab packaging 2011-01-13 08:03:18 -08:00
utsname.c ns proc: Add support for the uts namespace 2011-05-10 14:35:35 -07:00
utsname_sysctl.c
wait.c Fix common misspellings 2011-03-31 11:26:23 -03:00
watchdog.c kernel/watchdog.c: Use proper ANSI C prototypes 2011-05-23 21:07:40 -07:00
workqueue.c Merge branch 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2011-05-24 11:53:42 -07:00
workqueue_sched.h