04 Jul, 2007
1 commit
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The clock_was_set() call in seconds_overflow() which happens only when
leap seconds are inserted / deleted is wrong in two aspects:1. it results in a call to on_each_cpu() with interrupts disabled
2. it is potential deadlock source vs. call_lock in smp_call_function()The only possible side effect of the removal might be, that an absolute
CLOCK_REALTIME timer fires 1 second too late, in the rare case of leap
second deletion and an absolute CLOCK_REALTIME timer which expires in
the affected time frame. It will never fire too early.This was probably observed by the reporter of a June 30th -> July 1st
hang: http://lkml.org/lkml/2007/7/3/103A similar problem was observed by Dave Jones, who provided a screen shot
with a lockdep back trace, which allowed to analyse the problem.Signed-off-by: Thomas Gleixner
Acked-by: Ingo Molnar
Signed-off-by: Linus Torvalds
01 Jun, 2007
2 commits
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Make timer-stats have almost zero overhead when enabled in the config but
not used. (this way distros can enable it more easily)Also update the documentation about overhead of timer_stats - it was
written for the first version which had a global lock and a linear list
walk based lookup ;-)Signed-off-by: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Fix two races in the timer stats lookup code. One by ensuring that the
initialization of a new entry is finished upon insertion of that entry.
The other by cleaning up the hash table when the entries array is cleared,
so that we don't have any "pre-inserted" entries.Thanks to Eric Dumazet for reminding me of the memory barriers.
Signed-off-by: Bjorn Steinbrink
Signed-off-by: Ian Kumlien
Acked-by: Ingo Molnar
Cc: Eric Dumazet
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 May, 2007
1 commit
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get_next_timer_interrupt() returns a delta of (LONG_MAX > 1) in case
there is no timer pending. On 64 bit machines this results in a
multiplication overflow in tick_nohz_stop_sched_tick().Reported by: Dave Miller
Make the return value a constant and limit the return value to a 32 bit
value.When the max timeout value is returned, we can safely stop the tick
timer device. The max jiffies delta results in a 12 days timeout for
HZ=1000.In the long term the get_next_timer_interrupt() code needs to be
reworked to return ktime instead of jiffies, but we have to wait until
the last users of the original NO_IDLE_HZ code are converted.Signed-off-by: Thomas Gleixner
Acked-off-by: David S. Miller
Signed-off-by: Linus Torvalds
24 May, 2007
2 commits
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The warning in the NOHZ code, which triggers when a CPU goes idle with
softirqs pending can fill up the logs quite quickly. Rate limit the output
until we found the root cause of that problem.Signed-off-by: Thomas Gleixner
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Booting a SMP kernel with maxcpus=1 on a SMP system leads to a hard hang,
because ACPI ignores the maxcpus setting and sends timer broadcast info for
the offline CPUs. This results in a stuck for ever call to
smp_call_function_single() on an offline CPU.Ignore the bogus information and print a kernel error to remind ACPI
folks to fix it.Signed-off-by: Thomas Gleixner
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 May, 2007
1 commit
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First thing mm.h does is including sched.h solely for can_do_mlock() inline
function which has "current" dereference inside. By dealing with can_do_mlock()
mm.h can be detached from sched.h which is good. See below, why.This patch
a) removes unconditional inclusion of sched.h from mm.h
b) makes can_do_mlock() normal function in mm/mlock.c
c) exports can_do_mlock() to not break compilation
d) adds sched.h inclusions back to files that were getting it indirectly.
e) adds less bloated headers to some files (asm/signal.h, jiffies.h) that were
getting them indirectlyNet result is:
a) mm.h users would get less code to open, read, preprocess, parse, ... if
they don't need sched.h
b) sched.h stops being dependency for significant number of files:
on x86_64 allmodconfig touching sched.h results in recompile of 4083 files,
after patch it's only 3744 (-8.3%).Cross-compile tested on
all arm defconfigs, all mips defconfigs, all powerpc defconfigs,
alpha alpha-up
arm
i386 i386-up i386-defconfig i386-allnoconfig
ia64 ia64-up
m68k
mips
parisc parisc-up
powerpc powerpc-up
s390 s390-up
sparc sparc-up
sparc64 sparc64-up
um-x86_64
x86_64 x86_64-up x86_64-defconfig x86_64-allnoconfigas well as my two usual configs.
Signed-off-by: Alexey Dobriyan
Signed-off-by: Linus Torvalds
15 May, 2007
2 commits
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lockdep complains about the lock nesting of clocksource and watchdog lock
in the resume path.Change the resume marker to a bit operation and remove the lock from this
path.Signed-off-by: Thomas Gleixner
Cc: john stultz
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The time keeping code move to kernel/time/timekeeping.c broke the
clocksource resume logic patch, which got applied to the old file by a
fuzzy application. Fix it up and move the clocksource_resume() call to
the appropriate place.Signed-off-by: Thomas Gleixner
[ tssk, tssk, everybody should use --fuzz=0 ]
Signed-off-by: Linus Torvalds
10 May, 2007
3 commits
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We need to make sure that the clocksources are resumed, when timekeeping is
resumed. The current resume logic does not guarantee this.Add a resume function pointer to the clocksource struct, so clocksource
drivers which need to reinitialize the clocksource can provide a resume
function.Add a resume function, which calls the maybe available clocksource resume
functions and resets the watchdog function, so a stable TSC can be used
accross suspend/resume.Signed-off-by: Thomas Gleixner
Cc: john stultz
Cc: Andi Kleen
Cc: Ingo Molnar
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
u64 and s64 are not necessarily 'long long' on some 64-bit
platforms, so explicit the type to kill the compiler warnings.Also consistently use '%Lu' which is unsigned.
Signed-off-by: David S. Miller
Cc: Thomas Gleixner
Cc: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There's more that need fixing, and fix my own subject spelling error too.
Signed-off-by: Daniel Walker
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 May, 2007
5 commits
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Fix the process idle load balancing in the presence of dynticks. cpus for
which ticks are stopped will sleep till the next event wakes it up.
Potentially these sleeps can be for large durations and during which today,
there is no periodic idle load balancing being done.This patch nominates an owner among the idle cpus, which does the idle load
balancing on behalf of the other idle cpus. And once all the cpus are
completely idle, then we can stop this idle load balancing too. Checks added
in fast path are minimized. Whenever there are busy cpus in the system, there
will be an owner(idle cpu) doing the system wide idle load balancing.Open items:
1. Intelligent owner selection (like an idle core in a busy package).
2. Merge with rcu's nohz_cpu_mask?Signed-off-by: Suresh Siddha
Acked-by: Ingo Molnar
Cc: Thomas Gleixner
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
While the !highres/!dyntick code assigns the duty of the do_timer() call to
one specific CPU, this was dropped in the highres/dyntick part during
development.Steven Rostedt discovered the xtime lock contention on highres/dyntick due
to several CPUs trying to update jiffies.Add the single CPU assignement back. In the dyntick case this needs to be
handled carefully, as the CPU which has the do_timer() duty must drop the
assignement and let it be grabbed by another CPU, which is active.
Otherwise the do_timer() calls would not happen during the long sleep.Signed-off-by: Thomas Gleixner
Acked-by: Ingo Molnar
Cc: Steven Rostedt
Acked-by: Mark Lord
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
kallsyms_lookup() can go iterating over modules list unprotected which is OK
for emergency situations (oops), but not OK for regular stuff like
/proc/*/wchan.Introduce lookup_symbol_name()/lookup_module_symbol_name() which copy symbol
name into caller-supplied buffer or return -ERANGE. All copying is done with
module_mutex held, so...Signed-off-by: Alexey Dobriyan
Cc: Rusty Russell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Several kallsyms_lookup() pass dummy arguments but only need, say, module's
name. Make kallsyms_lookup() accept NULLs where possible.Also, makes picture clearer about what interfaces are needed for all symbol
resolving business.Signed-off-by: Alexey Dobriyan
Cc: Rusty Russell
Acked-by: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Move the timekeeping code out of kernel/timer.c and into
kernel/time/timekeeping.c. I made no cleanups or other changes in transit.[akpm@linux-foundation.org: build fix]
Signed-off-by: John Stultz
Cc: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Apr, 2007
1 commit
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In debugging a problem w/ the -rt tree, I noticed that on systems that mark
the tsc as unstable before it is registered, the TSC would still be
selected and used for a short period of time. Digging in it looks to be a
result of the mix of the clocksource list changes and my clocksource
initialization changes.With the -rt tree, using a bad TSC, even for a short period of time can
results in a hang at boot. I was not able to reproduce this hang w/
mainline, but I'm not completely certain that someone won't trip on it.This patch resolves the issue by initializing the jiffies clocksource
earlier so a bad TSC won't get selected just because nothing else is yet
registered.Signed-off-by: John Stultz
Acked-by: Thomas Gleixner
Cc: Ingo Molnar
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
28 Mar, 2007
1 commit
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I've been seeing some odd NTP behavior recently on a few boxes and
finally narrowed it down to time_offset overflowing when converted to
SHIFT_UPDATE units (which was a side effect from my HZfreeNTP patch).This patch converts time_offset from a long to a s64 which resolves the
issue.[tglx@linutronix.de: signedness fixes]
Signed-off-by: John Stultz
Cc: Roman Zippel
Cc: john stultz
Cc: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Mar, 2007
1 commit
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The current sysfs support of clockevents does not obey the "only one
value per file" rule.The real fix is not 2.6.21 material. Therefor remove the sysfs support
for now.Signed-off-by: Thomas Gleixner
Acked-by: Ingo Molnar
Acked-by: Greg Kroah-Hartman
Signed-off-by: Linus Torvalds
26 Mar, 2007
1 commit
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The watchdog implementation excludes low res / non continuous
clocksources from being selected as a watchdog reference
unintentionally.Allow using jiffies/PIT as a watchdog reference as long as no better
clocksource is available. This is necessary to detect TSC breakage on
systems, which have no pmtimer/hpet.The main goal of the initial patch (preventing to switch to highres/nohz
when no reliable fallback clocksource is available) is still guaranteed
by the checks in clocksource_watchdog().Signed-off-by: Thomas Gleixner
Signed-off-by: Linus Torvalds
24 Mar, 2007
1 commit
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Fix the print formatting of three unsigned long fields in /proc/timer_list,
which are currently being formatted as signed long.Signed-off-by: James Morris
Acked-by: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Mar, 2007
1 commit
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I finally found a dual core box, which survives suspend/resume without
crashing in the middle of nowhere. Sigh, I never figured out from the
code and the bug reports what's going on.The observed hangs are caused by a stale state transition of the clock
event devices, which keeps the RCU synchronization away from completion,
when the non boot CPU is brought back up.The suspend/resume in oneshot mode needs the similar care as the
periodic mode during suspend to RAM. My assumption that the state
transitions during the different shutdown/bringups of s2disk would go
through the periodic boot phase and then switch over to highres resp.
nohz mode were simply wrong.Add the appropriate suspend / resume handling for the non periodic
modes.Signed-off-by: Thomas Gleixner
Signed-off-by: Linus Torvalds
07 Mar, 2007
1 commit
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The programming of periodic tick devices needs to be saved/restored
across suspend/resume - otherwise we might end up with a system coming
up that relies on getting a PIT (or HPET) interrupt, while those devices
default to 'no interrupts' after powerup. (To confuse things it worked
to a certain degree on some systems because the lapic gets initialized
as a side-effect of SMP bootup.)This suspend / resume thing was dropped unintentionally during the
last-minute -mm code reshuffling.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Signed-off-by: Linus Torvalds
05 Mar, 2007
1 commit
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This patch resolves the issue found here:
http://bugme.osdl.org/show_bug.cgi?id=7426The basic summary is:
Currently we register most of i386/x86_64 clocksources at module_init
time. Then we enable clocksource selection at late_initcall time. This
causes some problems for drivers that use gettimeofday for init
calibration routines (specifically the es1968 driver in this case),
where durring module_init, the only clocksource available is the low-res
jiffies clocksource. This may cause slight calibration errors, due to
the small sampling time used.It should be noted that drivers that require fine grained time may not
function on architectures that do not have better then jiffies
resolution timekeeping (there are a few). However, this does not
discount the reasonable need for such fine-grained timekeeping at init
time.Thus the solution here is to register clocksources earlier (ideally when
the hardware is being initialized), and then we enable clocksource
selection at fs_initcall (before device_initcall).This patch should probably get some testing time in -mm, since
clocksource selection is one of the most important issues for correct
timekeeping, and I've only been able to test this on a few of my own
boxes.Signed-off-by: John Stultz
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: "David S. Miller"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Feb, 2007
2 commits
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When clockevents_program_event() is given an expire time in the
past, it does not update dev->next_event, so this looping code
would loop forever once the first in-the-past expiration time
was used.Keep advancing "next" locally to fix this bug.
Acked-by: Thomas Gleixner
Signed-off-by: David S. Miller -
Acked-by: Thomas Gleixner
Signed-off-by: David S. Miller
20 Feb, 2007
2 commits
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The BUG_ON() in tick_nohz_stop_sched_tick() triggers on some boxen.
Remove the BUG_ON and print information about the pending softirq
to allow better debugging of the problem.Signed-off-by: Thomas Gleixner
Signed-off-by: Linus Torvalds -
When a CPU is needed for RCU the tick has to continue even when it was
stopped before.Signed-off-by: Ingo Molnar
Signed-off-by: Thomas Gleixner
Signed-off-by: Linus Torvalds
17 Feb, 2007
11 commits
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add /proc/timer_list, which prints all currently pending (high-res) timers,
all clock-event sources and their parameters in a human-readable form.Sample output:
Timer List Version: v0.1
HRTIMER_MAX_CLOCK_BASES: 2
now at 4246046273872 nsecscpu: 0
clock 0:
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1273998312645738432 nsecs
active timers:
clock 1:
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: , hrtimer_sched_tick, hrtimer_stop_sched_tick, swapper/0
# expires at 4246432689566 nsecs [in 386415694 nsecs]
#1: , hrtimer_wakeup, do_nanosleep, pcscd/2050
# expires at 4247018194689 nsecs [in 971920817 nsecs]
#2: , hrtimer_wakeup, do_nanosleep, irqbalance/1909
# expires at 4247351358392 nsecs [in 1305084520 nsecs]
#3: , hrtimer_wakeup, do_nanosleep, crond/2157
# expires at 4249097614968 nsecs [in 3051341096 nsecs]
#4: , it_real_fn, do_setitimer, syslogd/1888
# expires at 4251329900926 nsecs [in 5283627054 nsecs]
.expires_next : 4246432689566 nsecs
.hres_active : 1
.check_clocks : 0
.nr_events : 31306
.idle_tick : 4246020791890 nsecs
.tick_stopped : 1
.idle_jiffies : 986504
.idle_calls : 40700
.idle_sleeps : 36014
.idle_entrytime : 4246019418883 nsecs
.idle_sleeptime : 4178181972709 nsecscpu: 1
clock 0:
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1273998312645738432 nsecs
active timers:
clock 1:
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: , hrtimer_sched_tick, hrtimer_restart_sched_tick, swapper/0
# expires at 4246050084568 nsecs [in 3810696 nsecs]
#1: , hrtimer_wakeup, do_nanosleep, atd/2227
# expires at 4261010635003 nsecs [in 14964361131 nsecs]
#2: , hrtimer_wakeup, do_nanosleep, smartd/2332
# expires at 5469485798970 nsecs [in 1223439525098 nsecs]
.expires_next : 4246050084568 nsecs
.hres_active : 1
.check_clocks : 0
.nr_events : 24043
.idle_tick : 4246046084568 nsecs
.tick_stopped : 0
.idle_jiffies : 986510
.idle_calls : 26360
.idle_sleeps : 22551
.idle_entrytime : 4246043874339 nsecs
.idle_sleeptime : 4170763761184 nsecstick_broadcast_mask: 00000003
event_broadcast_mask: 00000001CPU#0's local event device:
Clock Event Device: lapic
capabilities: 0000000e
max_delta_ns: 807385544
min_delta_ns: 1443
mult: 44624025
shift: 32
set_next_event: lapic_next_event
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
.installed: 1
.expires: 4246432689566 nsecsCPU#1's local event device:
Clock Event Device: lapic
capabilities: 0000000e
max_delta_ns: 807385544
min_delta_ns: 1443
mult: 44624025
shift: 32
set_next_event: lapic_next_event
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
.installed: 1
.expires: 4246050084568 nsecsClock Event Device: hpet
capabilities: 00000007
max_delta_ns: 2147483647
min_delta_ns: 3352
mult: 61496110
shift: 32
set_next_event: hpet_next_event
set_mode: hpet_set_mode
event_handler: handle_nextevt_broadcastSigned-off-by: Ingo Molnar
Signed-off-by: Thomas Gleixner
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec[ cleanups and hrtimers support from Thomas Gleixner ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar
Signed-off-by: Thomas Gleixner
Cc: john stultz
Cc: Roman Zippel
Cc: Andi Kleen
Signed-off-by: Adrian Bunk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Implement high resolution timers on top of the hrtimers infrastructure and the
clockevents / tick-management framework. This provides accurate timers for
all hrtimer subsystem users.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With Ingo Molnar
Add functions to provide dynamic ticks and high resolution timers. The code
which keeps track of jiffies and handles the long idle periods is shared
between tick based and high resolution timer based dynticks. The dyntick
functionality can be disabled on the kernel commandline. Provide also the
infrastructure to support high resolution timers.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With Ingo Molnar
Add broadcast functionality, so per cpu clock event devices can be registered
as dummy devices or switched from/to broadcast on demand. The broadcast
function distributes the events via the broadcast function of the clock event
device. This is primarily designed to replace the switch apic timer to / from
IPI in power states, where the apic stops.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With Ingo Molnar
The tick-management code is the first user of the clockevents layer. It takes
clock event devices from the clock events core and uses them to provide the
periodic tick.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Architectures register their clock event devices, in the clock events core.
Users of the clockevents core can get clock event devices for their use. The
clockevents core code provides notification mechanisms for various clock
related management events.This allows to control the clock event devices without the architectures
having to worry about the details of function assignment. This is also a
preliminary for high resolution timers and dynamic ticks to allow the core
code to control the clock functionality without intrusive changes to the
architecture code.[Fixes-by: Ingo Molnar ]
Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: Roman Zippel
Cc: john stultz
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The TSC needs to be verified against another clocksource. Instead of using
hardwired assumptions of available hardware, provide a generic verification
mechanism. The verification uses the best available clocksource and handles
the usability for high resolution timers / dynticks of the clocksource which
needs to be verified.Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Using a flag filed allows to encode more than one information into a variable.
Preparatory patch for the generic clocksource verification.[mingo@elte.hu: convert vmitime.c to the new clocksource flag]
Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Enqueue clocksources in rating order to make selection of the clocksource
easier. Also check the match with an user override at enqueue time.Preparatory patch for the generic clocksource verification.
Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Distangle the NTP update from HZ. This is necessary for dynamic tick enabled
kernels.Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: john stultz
Cc: Roman Zippel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds