Commit Graph

328 Commits

Author SHA1 Message Date
Linus Torvalds 179b9145d5 Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  clocksource: Resume clocksource without taking the clocksource mutex
2009-09-26 10:14:41 -07:00
Martin Schwidefsky 89133f9350 clocksource: Resume clocksource without taking the clocksource mutex
git commit 75c5158f70 converted the clocksource spinlock to a
mutex. This causes the following BUG:

BUG: sleeping function called from invalid context at
kernel/mutex.c:280 in_atomic(): 0, irqs_disabled(): 1, pid: 2473,
name: pm-suspend 2 locks held by pm-suspend/2473:
 #0:  (&buffer->mutex){......}, at: [<ffffffff8115ab13>]
sysfs_write_file+0x3c/0x137
 #1:  (pm_mutex){......}, at: [<ffffffff810865b5>]
enter_state+0x39/0x130 Pid: 2473, comm: pm-suspend Not tainted 2.6.31
#1 Call Trace:
 [<ffffffff810792f0>] ? __debug_show_held_locks+0x22/0x24
 [<ffffffff8104a2ef>] __might_sleep+0x107/0x10b
 [<ffffffff8141fca9>] mutex_lock_nested+0x25/0x43
 [<ffffffff81073537>] clocksource_resume+0x1c/0x60
 [<ffffffff81072902>] timekeeping_resume+0x1e/0x1c8
 [<ffffffff812aee62>] __sysdev_resume+0x25/0xcf
 [<ffffffff812aef79>] sysdev_resume+0x6d/0xae
 [<ffffffff810864f8>] suspend_devices_and_enter+0x12b/0x1af
 [<ffffffff8108665b>] enter_state+0xdf/0x130
 [<ffffffff81085dc3>] state_store+0xb6/0xd3
 [<ffffffff81204c73>] kobj_attr_store+0x17/0x19
 [<ffffffff8115abd2>] sysfs_write_file+0xfb/0x137
 [<ffffffff811057d2>] vfs_write+0xae/0x10b
 [<ffffffff81208392>] ? __up_read+0x1a/0x7f
 [<ffffffff811058ef>] sys_write+0x4a/0x6e
 [<ffffffff81011b82>] system_call_fastpath+0x16/0x1b

clocksource_resume is called early in the resume process, there is
only one cpu, no processes are running and the interrupts are
disabled. It is therefore possible to resume the clocksources
without taking the clocksource mutex.

Reported-by: Xiaotian Feng <xtfeng@gmail.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Tested-by: Michal Schmidt <mschmidt@redhat.com>
Cc: Xiaotian Feng <xtfeng@gmail.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20090924172952.49697825@mschwide.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-24 22:37:53 +02:00
Zhaolei 57f1f0874f time: add function to convert between calendar time and broken-down time for universal use
There are many similar code in kernel for one object: convert time between
calendar time and broken-down time.

Here is some source I found:
  fs/ncpfs/dir.c
  fs/smbfs/proc.c
  fs/fat/misc.c
  fs/udf/udftime.c
  fs/cifs/netmisc.c
  net/netfilter/xt_time.c
  drivers/scsi/ips.c
  drivers/input/misc/hp_sdc_rtc.c
  drivers/rtc/rtc-lib.c
  arch/ia64/hp/sim/boot/fw-emu.c
  arch/m68k/mac/misc.c
  arch/powerpc/kernel/time.c
  arch/parisc/include/asm/rtc.h
  ...

We can make a common function for this type of conversion, At least we
can get following benefit:

1: Make kernel simple and unify
2: Easy to fix bug in converting code
3: Reduce clone of code in future
   For example, I'm trying to make ftrace display walltime,
   this patch will make me easy.

This code is based on code from glibc-2.6

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-09-24 07:20:56 -07:00
Linus Torvalds a03fdb7612 Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (34 commits)
  time: Prevent 32 bit overflow with set_normalized_timespec()
  clocksource: Delay clocksource down rating to late boot
  clocksource: clocksource_select must be called with mutex locked
  clocksource: Resolve cpu hotplug dead lock with TSC unstable, fix crash
  timers: Drop a function prototype
  clocksource: Resolve cpu hotplug dead lock with TSC unstable
  timer.c: Fix S/390 comments
  timekeeping: Fix invalid getboottime() value
  timekeeping: Fix up read_persistent_clock() breakage on sh
  timekeeping: Increase granularity of read_persistent_clock(), build fix
  time: Introduce CLOCK_REALTIME_COARSE
  x86: Do not unregister PIT clocksource on PIT oneshot setup/shutdown
  clocksource: Avoid clocksource watchdog circular locking dependency
  clocksource: Protect the watchdog rating changes with clocksource_mutex
  clocksource: Call clocksource_change_rating() outside of watchdog_lock
  timekeeping: Introduce read_boot_clock
  timekeeping: Increase granularity of read_persistent_clock()
  timekeeping: Update clocksource with stop_machine
  timekeeping: Add timekeeper read_clock helper functions
  timekeeping: Move NTP adjusted clock multiplier to struct timekeeper
  ...

Fix trivial conflict due to MIPS lemote -> loongson renaming.
2009-09-18 09:15:24 -07:00
Thomas Gleixner 54a6bc0b07 clocksource: Delay clocksource down rating to late boot
The down rating of clock sources in the early boot process via the
clock source watchdog mechanism can happen way before the per cpu
event queues are initialized. This leads to a boot crash on x86 when
the TSC is marked unstable in the SMP bring up.

The selection of a clock source for time keeping happens in the late
boot process so we can safely delay the list manipulation until
clocksource_done_booting() is called.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
2009-09-14 21:59:32 +02:00
Thomas Gleixner e6c733050f clocksource: clocksource_select must be called with mutex locked
The callers of clocksource_select must hold clocksource_mutex to
protect the clocksource_list.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
2009-09-14 21:59:32 +02:00
Martin Schwidefsky f79e0258ea clocksource: Resolve cpu hotplug dead lock with TSC unstable, fix crash
The watchdog timer is started after the watchdog clocksource
and at least one watched clocksource have been registered. The
clocksource work element watchdog_work is initialized just
before the clocksource timer is started. This is too late for
the clocksource_mark_unstable call from native_cpu_up. To fix
this use a static initializer for watchdog_work.

This resolves a boot crash reported by multiple people.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20090911153305.3fe9a361@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-11 20:17:18 +02:00
Thomas Gleixner 7285dd7fd3 clocksource: Resolve cpu hotplug dead lock with TSC unstable
Martin Schwidefsky analyzed it:
To register a clocksource the clocksource_mutex is acquired and if
necessary timekeeping_notify is called to install the clocksource as
the timekeeper clock. timekeeping_notify uses stop_machine which needs
to take cpu_add_remove_lock mutex.
Starting a new cpu is done with the cpu_add_remove_lock mutex held.
native_cpu_up checks the tsc of the new cpu and if the tsc is no good
clocksource_change_rating is called. Which needs the clocksource_mutex
and the deadlock is complete.

The solution is to replace the TSC via the clocksource watchdog
mechanism. Mark the TSC as unstable and schedule the watchdog work so
it gets removed in the watchdog thread context.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
2009-08-28 20:25:24 +02:00
Hiroshi Shimamoto 36d47481b3 timekeeping: Fix invalid getboottime() value
Don't use timespec_add_safe() with wall_to_monotonic, because
wall_to_monotonic has negative values which will cause overflow
in timespec_add_safe(). That makes btime in /proc/stat invalid.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <4A937FDE.4050506@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-25 09:09:02 +02:00
john stultz da15cfdae0 time: Introduce CLOCK_REALTIME_COARSE
After talking with some application writers who want very fast, but not
fine-grained timestamps, I decided to try to implement new clock_ids
to clock_gettime(): CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE
which returns the time at the last tick. This is very fast as we don't
have to access any hardware (which can be very painful if you're using
something like the acpi_pm clocksource), and we can even use the vdso
clock_gettime() method to avoid the syscall. The only trade off is you
only get low-res tick grained time resolution.

This isn't a new idea, I know Ingo has a patch in the -rt tree that made
the vsyscall gettimeofday() return coarse grained time when the
vsyscall64 sysctrl was set to 2. However this affects all applications
on a system.

With this method, applications can choose the proper speed/granularity
trade-off for themselves.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: nikolag@ca.ibm.com
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: arjan@infradead.org
Cc: jonathan@jonmasters.org
LKML-Reference: <1250734414.6897.5.camel@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-21 21:43:46 +02:00
Suresh Siddha f833bab87f clockevent: Prevent dead lock on clockevents_lock
Currently clockevents_notify() is called with interrupts enabled at
some places and interrupts disabled at some other places.

This results in a deadlock in this scenario.

cpu A holds clockevents_lock in clockevents_notify() with irqs enabled
cpu B waits for clockevents_lock in clockevents_notify() with irqs disabled
cpu C doing set_mtrr() which will try to rendezvous of all the cpus.

This will result in C and A come to the rendezvous point and waiting
for B. B is stuck forever waiting for the spinlock and thus not
reaching the rendezvous point.

Fix the clockevents code so that clockevents_lock is taken with
interrupts disabled and thus avoid the above deadlock.

Also call lapic_timer_propagate_broadcast() on the destination cpu so
that we avoid calling smp_call_function() in the clockevents notifier
chain.

This issue left us wondering if we need to change the MTRR rendezvous
logic to use stop machine logic (instead of smp_call_function) or add
a check in spinlock debug code to see if there are other spinlocks
which gets taken under both interrupts enabled/disabled conditions.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: "Brown Len" <len.brown@intel.com>
LKML-Reference: <1250544899.2709.210.camel@sbs-t61.sc.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-19 18:15:10 +02:00
Martin Schwidefsky 01548f4d3e clocksource: Avoid clocksource watchdog circular locking dependency
stop_machine from a multithreaded workqueue is not allowed because
of a circular locking dependency between cpu_down and the workqueue
execution. Use a kernel thread to do the clocksource downgrade.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: john stultz <johnstul@us.ibm.com>
LKML-Reference: <20090818170942.3ab80c91@skybase>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-19 12:00:56 +02:00
Thomas Gleixner d0981a1b21 clocksource: Protect the watchdog rating changes with clocksource_mutex
Martin pointed out that commit 6ea41d2529 (clocksource: Call
clocksource_change_rating() outside of watchdog_lock) has a
theoretical reference count problem. The calls to
clocksource_change_rating() are now done outside of the clocksource
mutex and outside of the watchdog lock. A concurrent
clocksource_unregister() could remove the clock.

Split out the code which changes the rating from
clocksource_change_rating() into __clocksource_change_rating().

Protect the clocksource_watchdog_work() code sequence with the
clocksource_mutex() and call __clocksource_change_rating().

LKML-Reference: <alpine.LFD.2.00.0908171038420.2782@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
2009-08-19 11:42:48 +02:00
Amerigo Wang de809347ae timers: Drop write permission on /proc/timer_list
/proc/timer_list and /proc/slabinfo are not supposed to be
written, so there should be no write permissions on it.

Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: linux-mm@kvack.org
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20090817094525.6355.88682.sendpatchset@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-17 11:47:31 +02:00
Thomas Gleixner 6ea41d252f clocksource: Call clocksource_change_rating() outside of watchdog_lock
The changes to the watchdog logic introduced a lock inversion between
watchdog_lock and clocksource_mutex. Change the rating outside of
watchdog_lock to avoid it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 13:20:42 +02:00
Martin Schwidefsky 23970e389e timekeeping: Introduce read_boot_clock
Add the new function read_boot_clock to get the exact time the system
has been started. For architectures without support for exact boot
time a new weak function is added that returns 0.  Use the exact boot
time to initialize wall_to_monotonic, or xtime if the read_boot_clock
returned 0.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.296703241@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:47 +02:00
Martin Schwidefsky d4f587c67f timekeeping: Increase granularity of read_persistent_clock()
The persistent clock of some architectures (e.g. s390) have a
better granularity than seconds. To reduce the delta between the
host clock and the guest clock in a virtualized system change the 
read_persistent_clock function to return a struct timespec.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.013873340@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 75c5158f70 timekeeping: Update clocksource with stop_machine
update_wall_time calls change_clocksource HZ times per second to check
if a new clock source is available. In close to 100% of all calls
there is no new clock. Replace the tick based check by an update done
with stop_machine.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134810.711836357@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 2ba2a3054f timekeeping: Add timekeeper read_clock helper functions
Add timekeeper_read_clock_ntp and timekeeper_read_clock_raw and use
them for getnstimeofday, ktime_get, ktime_get_ts and getrawmonotonic.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134810.435105711@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 0a54419836 timekeeping: Move NTP adjusted clock multiplier to struct timekeeper
The clocksource structure has two multipliers, the unmodified multiplier
clock->mult_orig and the NTP corrected multiplier clock->mult. The NTP
multiplier is misplaced in the struct clocksource, this is private
information of the timekeeping code. Add the mult field to the struct
timekeeper to contain the NTP corrected value, keep the unmodifed
multiplier in clock->mult and remove clock->mult_orig.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134810.149047645@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 23ce72117c timekeeping: Add xtime_shift and ntp_error_shift to struct timekeeper
The xtime_nsec value in the timekeeper structure is shifted by a few
bits to improve precision. This happens to be the same value as the
clock->shift. To improve readability add xtime_shift to the timekeeper
and use it instead of the clock->shift. Likewise add ntp_error_shift
and replace all (NTP_SCALE_SHIFT - clock->shift) expressions.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.871899606@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 155ec60226 timekeeping: Introduce struct timekeeper
Add struct timekeeper to keep the internal values timekeeping.c needs
in regard to the currently selected clock source. This moves the
timekeeping intervals, xtime_nsec and the ntp error value from struct
clocksource to struct timekeeper. The raw_time is removed from the
clocksource as well. It gets treated like xtime as a global variable.
Eventually xtime raw_time should be moved to struct timekeeper.

[ tglx: minor cleanup ]

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.613209842@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky c55c87c892 clocksource: Move watchdog downgrade to a work queue thread
Move the downgrade of an unstable clocksource from the timer interrupt
context into the process context of a work queue thread. This is
needed to be able to do the clocksource switch with stop_machine.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.354926067@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky fb63a0ebe6 clocksource: Refactor clocksource watchdog
Refactor clocksource watchdog code to make it more readable. Add
clocksource_dequeue_watchdog to remove a clocksource from the watchdog
list when it is unregistered.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134809.110881699@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 0f8e8ef7c2 clocksource: Simplify clocksource watchdog resume logic
To resume the clocksource watchdog just remove the CLOCK_SOURCE_WATCHDOG
bit from the watched clocksource.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.880925790@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 8cf4e750f8 clocksource: Delay clocksource watchdog highres enablement
The clocksource watchdog marks a clock as highres capable before it
checked the deviation from the watchdog clocksource even for a single
time. Make sure that the deviation is at least checked once before
doing the switch to highres mode.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.627795883@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky f1b82746c1 clocksource: Cleanup clocksource selection
If a non high-resolution clocksource is first set as override clock
and then registered it becomes active even if the system is in one-shot
mode. Move the override check from sysfs_override_clocksource to the
clocksource selection. That fixes the bug and simplifies the code. The
check in clocksource_register for double registration of the same
clocksource is removed without replacement.

To find the initial clocksource a new weak function in jiffies.c is
defined that returns the jiffies clocksource. The architecture code
can then override the weak function with a more suitable clocksource,
e.g. the TOD clock on s390.

[ tglx: Folded in a fix from John Stultz ]

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.388024160@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:46 +02:00
Martin Schwidefsky 1be3967948 timekeeping: Move reset of cycle_last for tsc clocksource to tsc
change_clocksource resets the cycle_last value to zero then sets it to
a value read from the clocksource. The reset to zero is required only
for the TSC clocksource to make the read_tsc function work after a
resume. The reason is that the TSC read function uses cycle_last to
detect backwards going TSCs. In the resume case cycle_last contains
the TSC value from the last update before the suspend. On resume the
TSC starts counting from 0 again and would trip over the cycle_last
comparison.

This is subtle and surprising. Move the reset to a resume function in
the tsc code.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.142191175@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:45 +02:00
Martin Schwidefsky a0f7d48bfb timekeeping: Remove clocksource inline functions
The three inline functions clocksource_read, clocksource_enable and
clocksource_disable are simple wrappers of an indirect call plus the
copy from and to the mult_orig value. The functions are exclusively
used by the timekeeping code which has intimate knowledge of the
clocksource anyway. Therefore remove the inline functions. No
functional change.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134807.903108946@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:45 +02:00
John Stultz 31089c13bc timekeeping: Introduce timekeeping_leap_insert
Move the adjustment of xtime, wall_to_monotonic and the update of the
vsyscall variables to the timekeeping code.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
LKML-Reference: <20090814134807.609730216@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-15 10:55:45 +02:00
Thomas Gleixner 4cd1993f00 Merge branch 'linus' into timers/core
Reason: Martin's timekeeping cleanup series depends on both
timers/core and mainline changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-14 15:59:30 +02:00
Thomas Gleixner 79ef2bb014 clocksource: Prevent NULL pointer dereference
Writing a zero length string to sys/.../current_clocksource will cause
a NULL pointer dereference if the clock events system is in one shot
(highres or nohz) mode.

Pointed-out-by: Dan Carpenter <error27@gmail.com>
LKML-Reference: <alpine.DEB.2.00.0907191545580.12306@bicker>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-19 17:15:54 +02:00
Thomas Gleixner 6ff7041dbf hrtimer: Fix migration expiry check
The timer migration expiry check should prevent the migration of a
timer to another CPU when the timer expires before the next event is
scheduled on the other CPU. Migrating the timer might delay it because
we can not reprogram the clock event device on the other CPU. But the
code implementing that check has two flaws:

- for !HIGHRES the check compares the expiry value with the clock
  events device expiry value which is wrong for CLOCK_REALTIME based
  timers.

- the check is racy. It holds the hrtimer base lock of the target CPU,
  but the clock event device expiry value can be modified
  nevertheless, e.g. by an timer interrupt firing.

The !HIGHRES case is easy to fix as we can enqueue the timer on the
cpu which was selected by the load balancer. It runs the idle
balancing code once per jiffy anyway. So the maximum delay for the
timer is the same as when we keep the tick on the current cpu going.

In the HIGHRES case we can get the next expiry value from the hrtimer
cpu_base of the target CPU and serialize the update with the cpu_base
lock. This moves the lock section in hrtimer_interrupt() so we can set
next_event to KTIME_MAX while we are handling the expired timers and
set it to the next expiry value after we handled the timers under the
base lock. While the expired timers are processed timer migration is
blocked because the expiry time of the timer is always <= KTIME_MAX.

Also remove the now useless clockevents_get_next_event() function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-10 17:32:55 +02:00
Thomas Gleixner a40f262cc2 timekeeping: Move ktime_get() functions to timekeeping.c
The ktime_get() functions for GENERIC_TIME=n are still located in
hrtimer.c. Move them to time/timekeeping.c where they belong.

LKML-Reference: <new-submission>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-07 13:00:31 +02:00
Martin Schwidefsky 951ed4d36b timekeeping: optimized ktime_get[_ts] for GENERIC_TIME=y
The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
for GENERIC_TIME=y:

 0)               |  ktime_get() {
 0)               |    ktime_get_ts() {
 0)               |      getnstimeofday() {
 0)               |        read_tod_clock() {
 0)   0.601 us    |        }
 0)   1.938 us    |      }
 0)               |      set_normalized_timespec() {
 0)   0.602 us    |      }
 0)   4.375 us    |    }
 0)   5.523 us    |  }

Overall there are two read_seqbegin/read_seqretry loops and a lot of
unnecessary struct timespec calculations. ktime_get returns a nano second
value which is the sum of xtime, wall_to_monotonic and the nano second
delta from the clock source.

ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
clocksource_read:

 0)               |  ktime_get() {
 0)               |    read_tod_clock() {
 0)   0.610 us    |    }
 0)   1.977 us    |  }

It uses a single read_seqbegin/readseqretry loop and just adds everthing
to a nano second value.

ktime_get_ts is optimized in a similar fashion.

[ tglx: added WARN_ON(timekeeping_suspended) as in getnstimeofday() ]

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: john stultz <johnstul@us.ibm.com>
LKML-Reference: <20090707112728.3005244d@skybase>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-07 12:47:33 +02:00
Heiko Carstens 507e123151 timer stats: Optimize by adding quick check to avoid function calls
When the kernel is configured with CONFIG_TIMER_STATS but timer
stats are runtime disabled we still get calls to
__timer_stats_timer_set_start_info which initializes some
fields in the corresponding struct timer_list.

So add some quick checks in the the timer stats setup functions
to avoid function calls to __timer_stats_timer_set_start_info
when timer stats are disabled.

In an artificial workload that does nothing but playing ping
pong with a single tcp packet via loopback this decreases cpu
consumption by 1 - 1.5%.

This is part of a modified function trace output on SLES11:

 perl-2497  [00] 28630647177732388 [+  125]: sk_reset_timer <-tcp_v4_rcv
 perl-2497  [00] 28630647177732513 [+  125]: mod_timer <-sk_reset_timer
 perl-2497  [00] 28630647177732638 [+  125]: __timer_stats_timer_set_start_info <-mod_timer
 perl-2497  [00] 28630647177732763 [+  125]: __mod_timer <-mod_timer
 perl-2497  [00] 28630647177732888 [+  125]: __timer_stats_timer_set_start_info <-__mod_timer
 perl-2497  [00] 28630647177733013 [+   93]: lock_timer_base <-__mod_timer

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mustafa Mesanovic <mustafa.mesanovic@de.ibm.com>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <20090623153811.GA4641@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-24 11:15:09 +02:00
Linus Torvalds 38df92b8ce Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  NOHZ: Properly feed cpufreq ondemand governor
2009-06-20 10:51:44 -07:00
Linus Torvalds 19035e5b5d Merge branch 'timers-for-linus-migration' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-for-linus-migration' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  timers: Logic to move non pinned timers
  timers: /proc/sys sysctl hook to enable timer migration
  timers: Identifying the existing pinned timers
  timers: Framework for identifying pinned timers
  timers: allow deferrable timers for intervals tv2-tv5 to be deferred

Fix up conflicts in kernel/sched.c and kernel/timer.c manually
2009-06-15 10:06:19 -07:00
Linus Torvalds f9db6e0951 Merge branch 'timers-for-linus-clockevents' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-for-linus-clockevents' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  clockevent: export register_device and delta2ns
  clockevents: tick_broadcast_device can become static
2009-06-15 09:58:50 -07:00
Linus Torvalds 3f27c0d2a4 Merge branch 'timers-for-linus-clocksource' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-for-linus-clocksource' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  clocksource: prevent selection of low resolution clocksourse also for nohz=on
  clocksource: sanity check sysfs clocksource changes
2009-06-15 09:58:33 -07:00
Thomas Gleixner cd6d95d844 clocksource: prevent selection of low resolution clocksourse also for nohz=on
commit 3f68535ada (clocksource: sanity check sysfs clocksource
changes) prevents selection of non high resolution capable
clocksources when high resolution mode is active, but did not take
into account that the same rules apply for highres=off nohz=on.

Check the tick device mode instead of hrtimer_hres_active() to verify
whether the system needs to be protected from a switch to jiffies or
other non highres capable clock sources.

Reported-by: Luming Yu <luming.yu@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-06-13 12:00:26 +02:00
john stultz 3f68535ada clocksource: sanity check sysfs clocksource changes
Thomas, Andrew and Ingo pointed out that we don't have any safety checks
in the clocksource sysfs entries to make sure sysadmins don't try to
change the clocksource to a non high-res timer capable clocksource (such
as jiffies) when high-res timers (HRT) is enabled.  Doing so will likely
hang a system.

Correct this by filtering non HRT clocksources from available_clocksources
and not accepting non HRT clocksources with HRT enabled.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-06-11 11:24:52 +02:00
Paul Mundt cf9fe114e3 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 2009-06-11 09:01:14 +03:00
Eero Nurkkala f2e21c9610 NOHZ: Properly feed cpufreq ondemand governor
A call from irq_exit() may occasionally pause the timing
info for cpufreq ondemand governor. This results in the
cpufreq ondemand governor to fail to calculate the 
system load properly. Thus, relocate the checks for this
particular case to keep the governor always functional.

Signed-off-by: Eero Nurkkala <ext-eero.nurkkala@nokia.com>
Reported-by: Tero Kristo <tero.kristo@nokia.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-05-27 15:33:43 +02:00
Paul Mundt 5f8371cec9 Merge branches 'sh/stable-updates' and 'sh/sparseirq' 2009-05-22 13:29:37 +09:00
Thomas Gleixner dce48a84ad sched, timers: move calc_load() to scheduler
Dimitri Sivanich noticed that xtime_lock is held write locked across
calc_load() which iterates over all online CPUs. That can cause long
latencies for xtime_lock readers on large SMP systems. 

The load average calculation is an rough estimate anyway so there is
no real need to protect the readers vs. the update. It's not a problem
when the avenrun array is updated while a reader copies the values.

Instead of iterating over all online CPUs let the scheduler_tick code
update the number of active tasks shortly before the avenrun update
happens. The avenrun update itself is handled by the CPU which calls
do_timer().

[ Impact: reduce xtime_lock write locked section ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
2009-05-15 15:32:45 +02:00
Arun R Bharadwaj eea08f32ad timers: Logic to move non pinned timers
* Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-04-16 12:11:36]:

This patch migrates all non pinned timers and hrtimers to the current
idle load balancer, from all the idle CPUs. Timers firing on busy CPUs
are not migrated.

While migrating hrtimers, care should be taken to check if migrating
a hrtimer would result in a latency or not. So we compare the expiry of the
hrtimer with the next timer interrupt on the target cpu and migrate the
hrtimer only if it expires *after* the next interrupt on the target cpu.
So, added a clockevents_get_next_event() helper function to return the
next_event on the target cpu's clock_event_device.

[ tglx: cleanups and simplifications ]

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-05-13 16:52:42 +02:00
Arun R Bharadwaj 5c333864a6 timers: Identifying the existing pinned timers
* Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-04-16 12:11:36]:

The following pinned hrtimers have been identified and marked:
1)sched_rt_period_timer
2)tick_sched_timer
3)stack_trace_timer_fn

[ tglx: fixup the hrtimer pinned mode ]

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-05-13 16:52:42 +02:00
Magnus Damm c81fc2c331 clockevent: export register_device and delta2ns
Export the following symbols using EXPORT_SYMBOL_GPL:
 - clockevent_delta2ns
 - clockevents_register_device

This allows us to build SuperH clockevent and clocksource
drivers as modules, see drivers/clocksource/sh_*.c

[ Impact: allow modular build of clockevent drivers ]

Signed-off-by: Magnus Damm <damm@igel.co.jp>
LKML-Reference: <20090501055247.8286.64067.sendpatchset@rx1.opensource.se>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-05-02 11:51:07 +02:00
john stultz 7d27558c41 timekeeping: create arch_gettimeoffset infrastructure
Some arches don't supply their own clocksource. This is mainly the
case in architectures that get their inter-tick times by reading the
counter on their interval timer.  Since these timers wrap every tick,
they're not really useful as clocksources.  Wrapping them to act like
one is possible but not very efficient. So we provide a callout these
arches can implement for use with the jiffies clocksource to provide
finer then tick granular time.

[ Impact: ease the migration to generic time keeping ]

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-05-02 11:45:15 +02:00