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John Stultz b3c869d35b jiffies: Remove compile time assumptions about CLOCK_TICK_RATE 
CLOCK_TICK_RATE is used to accurately caclulate exactly how
a tick will be at a given HZ.

This is useful, because while we'd expect NSEC_PER_SEC/HZ,
the underlying hardware will have some granularity limit,
so we won't be able to have exactly HZ ticks per second.

This slight error can cause timekeeping quality problems
when using the jiffies or other jiffies driven clocksources.
Thus we currently use compile time CLOCK_TICK_RATE value to
generate SHIFTED_HZ and NSEC_PER_JIFFIES, which we then use
to adjust the jiffies clocksource to correct this error.

Unfortunately though, since CLOCK_TICK_RATE is a compile
time value, and the jiffies clocksource is registered very
early during boot, there are a number of cases where there
are different possible hardware timers that have different
tick rates. This causes problems in cases like ARM where
there are numerous different types of hardware, each having
their own compile-time CLOCK_TICK_RATE, making it hard to
accurately support different hardware with a single kernel.

For the most part, this doesn't matter all that much, as not
too many systems actually utilize the jiffies or jiffies driven
clocksource. Usually there are other highres clocksources
who's granularity error is negligable.

Even so, we have some complicated calcualtions that we do
everywhere to handle these edge cases.

This patch removes the compile time SHIFTED_HZ value, and
introduces a register_refined_jiffies() function. This results
in the default jiffies clock as being assumed a perfect HZ
freq, and allows archtectures that care about jiffies accuracy
to call register_refined_jiffies() with the tick rate, specified
dynamically at boot.

This allows us, where necessary, to not have a compile time
CLOCK_TICK_RATE constant, simplifies the jiffies code, and
still provides a way to have an accurate jiffies clock.

NOTE: Since this patch does not add register_refinied_jiffies()
calls for every arch, it may cause time quality regressions
in some cases. Its likely these will not be noticable, but
if they are an issue, adding the following to the end of
setup_arch() should resolve the regression:
	register_refinied_jiffies(CLOCK_TICK_RATE)

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2012-09-24 12:38:05 -04:00
..
debug kernel/debug: Make use of KGDB_REASON_NMI 2012-07-31 08:16:43 -05:00
events perf/trace: Add ability to set a target task for events 2012-07-31 17:02:05 +02:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-08-03 10:56:44 -07:00
power Revert "NMI watchdog: fix for lockup detector breakage on resume" 2012-08-08 20:49:45 +02:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-08-20 10:35:05 -07:00
time jiffies: Remove compile time assumptions about CLOCK_TICK_RATE 2012-09-24 12:38:05 -04:00
trace tracing/syscalls: Fix perf syscall tracing when syscall_nr == -1 2012-08-17 15:19:46 -04:00
.gitignore
acct.c Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-01-08 12:19:57 -08:00
async.c [SCSI] async: make async_synchronize_full() flush all work regardless of domain 2012-07-20 09:07:37 +01:00
audit_tree.c audit: clean up refcounting in audit-tree 2012-08-15 12:55:22 +02:00
audit_watch.c get rid of kern_path_parent() 2012-07-14 16:35:02 +04:00
audit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-08-01 10:26:23 -07:00
audit.h audit: remove AUDIT_SETUP_CONTEXT as it isn't used 2012-01-17 16:16:57 -05:00
auditfilter.c audit: allow interfield comparison in audit rules 2012-01-17 16:17:01 -05:00
auditsc.c seccomp: remove duplicated failure logging 2012-04-14 11:13:20 +10:00
backtracetest.c
bounds.c
capability.c userns: Teach inode_capable to understand inodes whose uids map to other namespaces. 2012-05-15 14:59:24 -07:00
cgroup_freezer.c cgroup: convert all non-memcg controllers to the new cftype interface 2012-04-01 12:09:55 -07:00
cgroup.c Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-07-24 17:47:44 -07:00
compat.c new helper: sigsuspend() 2012-05-21 23:52:30 -04:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu_pm.c kernel/cpu_pm.c: fix various typos 2012-05-31 17:49:27 -07:00
cpu.c mm/hotplug: correctly setup fallback zonelists when creating new pgdat 2012-07-31 18:42:44 -07:00
cpuset.c cpusets: Remove/update outdated comments 2012-07-24 13:53:28 +02:00
crash_dump.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cred.c keys: kill task_struct->replacement_session_keyring 2012-05-23 22:11:41 -04:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
elfcore.c
exec_domain.c
exit.c posix_types.h: Cleanup stale __NFDBITS and related definitions 2012-07-26 13:36:43 -07:00
extable.c extable: Skip sorting if sorted at build time. 2012-04-19 15:06:55 -07:00
fork.c uprobes: Fix mmap_region()'s mm->mm_rb corruption if uprobe_mmap() fails 2012-08-21 11:48:12 +02:00
freezer.c PM / Freezer: Remove references to TIF_FREEZE in comments 2012-03-04 23:08:54 +01:00
futex_compat.c futex: Mark get_robust_list as deprecated 2012-03-29 11:37:17 +02:00
futex.c futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi() 2012-07-24 16:02:57 +02:00
groups.c userns: Convert in_group_p and in_egroup_p to use kgid_t 2012-05-03 03:29:33 -07:00
hrtimer.c hrtimer: Update hrtimer base offsets each hrtimer_interrupt 2012-07-11 23:34:39 +02:00
hung_task.c hung task debugging: Inject NMI when hung and going to panic 2012-04-25 12:39:25 +02:00
irq_work.c irq_work: fix compile failure on tile from missing include 2012-04-13 13:15:16 -04:00
itimer.c itimer: Use printk_once instead of WARN_ONCE 2012-04-10 11:00:30 +02:00
jump_label.c static keys: Inline the static_key_enabled() function 2012-02-28 20:01:08 +01:00
kallsyms.c vsprintf: fix %ps on non symbols when using kallsyms 2012-05-29 16:22:32 -07:00
kcmp.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
Kconfig.preempt locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
kexec.c kdump: append newline to the last lien of vmcoreinfo note 2012-07-30 17:25:20 -07:00
kfifo.c [media] kernel:kfifo: export __kfifo_max_r symbol 2012-04-11 18:24:37 -03:00
kmod.c kmod: avoid deadlock from recursive kmod call 2012-07-30 17:25:20 -07:00
kprobes.c kprobes: return proper error code from register_kprobe() 2012-03-05 15:49:42 -08:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed 2012-07-22 10:15:28 -07:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lglock.c brlocks/lglocks: turn into functions 2012-05-29 23:28:41 -04:00
lockdep_internals.h
lockdep_proc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_states.h
lockdep.c lockdep: Add CPU-idle/offline warning to lockdep-RCU splat 2012-02-21 09:06:06 -08:00
Makefile Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-06-01 10:34:35 -07:00
module.c Guard check in module loader against integer overflow 2012-05-23 22:28:53 +09:30
mutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex-debug.h
mutex.c sched/rt: Use schedule_preempt_disabled() 2012-03-01 10:28:03 +01:00
mutex.h
notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nsproxy.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
padata.c padata: Fix cpu hotplug 2012-03-29 19:52:46 +08:00
panic.c panic: fix a possible deadlock in panic() 2012-07-30 17:25:13 -07:00
params.c params: replace printk(KERN_<LVL>...) with pr_<lvl>(...) 2012-05-04 17:28:18 -07:00
pid_namespace.c pidns: guarantee that the pidns init will be the last pidns process reaped 2012-06-20 14:39:36 -07:00
pid.c mm: add a low limit to alloc_large_system_hash 2012-05-24 00:28:21 -04:00
posix-cpu-timers.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
posix-timers.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
printk.c printk: Fix calculation of length used to discard records 2012-08-12 21:25:50 +03:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c userns: Convert ptrace, kill, set_priority permission checks to work with kuids and kgids 2012-05-03 03:28:51 -07:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Allow nesting of rcu_idle_enter() and rcu_idle_exit() 2012-02-21 09:06:12 -08:00
rcupdate.c rcu: Consolidate tree/tiny __rcu_read_{,un}lock() implementations 2012-07-02 12:34:23 -07:00
rcutiny_plugin.h rcu: Fix code-style issues involving "else" 2012-07-06 06:01:48 -07:00
rcutiny.c rcu: Fix rcu_is_cpu_idle() #ifdef in TINY_RCU 2012-07-02 12:34:25 -07:00
rcutorture.c rcu: Fix broken strings in RCU's source code. 2012-07-06 06:01:49 -07:00
rcutree_plugin.h rcu: Fix code-style issues involving "else" 2012-07-06 06:01:48 -07:00
rcutree_trace.c rcu: Fix broken strings in RCU's source code. 2012-07-06 06:01:49 -07:00
rcutree.c rcu: Fix code-style issues involving "else" 2012-07-06 06:01:48 -07:00
rcutree.h Merge branches 'bigrtm.2012.07.04a', 'doctorture.2012.07.02a', 'fixes.2012.07.06a' and 'fnh.2012.07.02a' into HEAD 2012-07-06 05:59:30 -07:00
relay.c splice: fix racy pipe->buffers uses 2012-06-13 21:16:42 +02:00
res_counter.c rescounters: add res_counter_uncharge_until() 2012-05-29 16:22:27 -07:00
resource.c resource: make sure requested range is included in the root range 2012-07-30 17:25:21 -07:00
rtmutex_common.h
rtmutex-debug.c lockdep, rtmutex, bug: Show taint flags on error 2011-12-06 08:16:49 +01:00
rtmutex-debug.h
rtmutex-tester.c rtmutex-tester: convert sysdev_class to a regular subsystem 2011-12-14 14:54:22 -08:00
rtmutex.c Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" 2011-12-11 10:33:18 -08:00
rtmutex.h
rwsem.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
seccomp.c seccomp: fix build warnings when there is no CONFIG_SECCOMP_FILTER 2012-04-18 12:24:52 +10:00
semaphore.c semaphore: fix improper comment reference to mutex 2012-04-05 17:15:55 -07:00
signal.c signal: make sure we don't get stopped with pending task_work 2012-07-22 23:57:54 +04:00
smp.c smp: Remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]() 2012-06-05 17:27:14 +02:00
smpboot.c smpboot, idle: Fix comment mismatch over idle_threads_init() 2012-05-24 22:58:08 +02:00
smpboot.h smpboot: Remove leftover declaration 2012-06-11 15:07:52 +02:00
softirq.c mm: allow PF_MEMALLOC from softirq context 2012-07-31 18:42:45 -07:00
spinlock.c locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
srcu.c rcu: Implement per-domain single-threaded call_srcu() state machine 2012-04-30 10:48:25 -07:00
stacktrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stop_machine.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sys_ni.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
sys.c kernel/sys.c: avoid argv_free(NULL) 2012-07-30 17:25:13 -07:00
sysctl_binary.c mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads 2012-07-31 18:42:40 -07:00
sysctl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-08-01 10:26:23 -07:00
task_work.c task_work: add a scheduling point in task_work_run() 2012-08-21 09:11:44 -07:00
taskstats.c taskstats: check nla_reserve() return 2012-07-30 17:25:21 -07:00
test_kprobes.c
time.c time: Remove bogus comments 2012-03-15 18:17:55 -07:00
timeconst.pl
timer.c alpha: take a bunch of syscalls into osf_sys.c 2012-08-19 08:41:19 -07:00
tracepoint.c static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() 2012-02-24 10:05:59 +01:00
tsacct.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
uid16.c userns: Convert setting and getting uid and gid system calls to use kuid and kgid 2012-05-03 03:28:41 -07:00
up.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user_namespace.c userns: Store uid and gid values in struct cred with kuid_t and kgid_t types 2012-05-03 03:28:38 -07:00
user-return-notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user.c userns: Silence silly gcc warning. 2012-05-19 15:44:40 -06:00
utsname_sysctl.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
utsname.c userns: Use cred->user_ns instead of cred->user->user_ns 2012-04-07 16:55:51 -07:00
wait.c lockdep/waitqueues: Add better annotation 2011-12-21 10:07:39 +01:00
watchdog.c Revert "NMI watchdog: fix for lockup detector breakage on resume" 2012-08-08 20:49:45 +02:00
workqueue_sched.h
workqueue.c workqueue: fix possible idle worker depletion across CPU hotplug 2012-09-10 10:05:54 -07:00