Commit Graph

18 Commits

Author SHA1 Message Date
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
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
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
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
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
Magnus Damm
2d68259db2 clockevents: let set_mode() setup delta information
Allow the set_mode() clockevent callback to decide and fill in delta
details such as shift, mult, max_delta_ns and min_delta_ns.

With this change the clockevent can be registered without delta details
which allows us to keep the parent clock disabled until the clockevent
gets setup using set_mode().

Letting set_mode() fill in or update delta details allows us to save
power by disabling the parent clock while the clockevent is unused.
This may however make the parent clock rate change, so next time the
clockevent gets enabled we need let set_mode() to update the detla
details accordingly. Doing it at registration time is not enough.

Furthermore, the delta details seem unused in the case of periodic-only
clockevent drivers, so this change also allows registration of such
drivers without the delta details filled in.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-01-16 12:27:39 +01:00
Rusty Russell
320ab2b0b1 cpumask: convert struct clock_event_device to cpumask pointers.
Impact: change calling convention of existing clock_event APIs

struct clock_event_timer's cpumask field gets changed to take pointer,
as does the ->broadcast function.

Another single-patch change.  For safety, we BUG_ON() in
clockevents_register_device() if it's not set.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
2008-12-13 21:20:26 +10:30
Thomas Gleixner
2344abbcbd clockevents: make device shutdown robust
The device shut down does not cleanup the next_event variable of the
clock event device. So when the device is reactivated the possible
stale next_event value can prevent the device to be reprogrammed as it
claims to wait on a event already.

This is the root cause of the resurfacing suspend/resume problem,
where systems need key press to come back to life.

Fix this by setting next_event to KTIME_MAX when the device is shut
down. Use a separate function for shutdown which takes care of that
and only keep the direct set mode call in the broadcast code, where we
can not touch the next_event value.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-09-16 13:47:02 -07:00
Venkatesh Pallipadi
7c1e768974 clockevents: prevent clockevent event_handler ending up handler_noop
There is a ordering related problem with clockevents code, due to which
clockevents_register_device() called after tickless/highres switch
will not work. The new clockevent ends up with clockevents_handle_noop as
event handler, resulting in no timer activity.

The problematic path seems to be

* old device already has hrtimer_interrupt as the event_handler
* new clockevent device registers with a higher rating
* tick_check_new_device() is called
  * clockevents_exchange_device() gets called
    * old->event_handler is set to clockevents_handle_noop
  * tick_setup_device() is called for the new device
    * which sets new->event_handler using the old->event_handler which is noop.

Change the ordering so that new device inherits the proper handler.

This does not have any issue in normal case as most likely all the clockevent
devices are setup before the highres switch. But, can potentially be affecting
some corner case where HPET force detect happens after the highres switch.
This was a problem with HPET in MSI mode code that we have been experimenting
with.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-05 11:11:51 +02:00
Li Zefan
3eb056764d time: fix typo in comments
Fix typo in comments.

BTW: I have to fix coding style in arch/ia64/kernel/time.c also, otherwise
checkpatch.pl will be complaining.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:29 -08:00
Li Zefan
0b858e6ff9 clockevent: simplify list operations
list_for_each_safe() suffices here.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:29 -08:00
Ingo Molnar
45fe4fe191 x86: make clockevents more robust
detect zero event-device multiplicators - they then cause
division-by-zero crashes if a clockevent has been initialized
incorrectly.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30 13:30:03 +01:00
Thomas Gleixner
167b1de3ee clockevents: warn once when program_event() is called with negative expiry
The hrtimer problem with large relative timeouts resulting in a
negative expiry time went unnoticed as there is no check in the
clockevents_program_event() code. Put a check there with a WARN_ONCE
to avoid such problems in the future.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-12-07 19:16:17 +01:00
Thomas Gleixner
de68d9b173 clockevents: Allow build w/o run-tine usage for migration purposes
Migration aid to allow preparatory patches which introduce not yet
used parts of clock events code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
2007-10-12 23:04:05 +02:00
Miao Xie
6ddfca9548 timer: remove clockevents_unregister_notifier
I find a function(clockevents_unregister_notifier) which is not called by
anything in tree.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-08-11 15:47:42 -07:00
Andi Kleen
78c1b06574 Remove clockevents_{release,request}_device
Not called by anything in tree.

Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 09:05:43 -07:00
Thomas Gleixner
291bc047e1 [PATCH] clockevents: remove bad designed sysfs support for now
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 <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-03-26 14:07:23 -07:00
Thomas Gleixner
d316c57ff6 [PATCH] clockevents: add core functionality
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 <mingo@elte.hu>]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 08:13:59 -08:00