linux-toradex.git/kernel/timer.c, branch v2.6.32.60 Linux kernel for Apalis and Colibri modules nohz: Fix get_next_timer_interrupt() vs cpu hotplug 2011-01-07T22:43:03+00:00 Heiko Carstens heiko.carstens@de.ibm.com 2010-12-01T09:11:09+00:00 4c3c55199aefa28fb657bd53d7b382fe464e33f5 commit dbd87b5af055a0cc9bba17795c9a2b0d17795389 upstream. This fixes a bug as seen on 2.6.32 based kernels where timers got enqueued on offline cpus. If a cpu goes offline it might still have pending timers. These will be migrated during CPU_DEAD handling after the cpu is offline. However while the cpu is going offline it will schedule the idle task which will then call tick_nohz_stop_sched_tick(). That function in turn will call get_next_timer_intterupt() to figure out if the tick of the cpu can be stopped or not. If it turns out that the next tick is just one jiffy off (delta_jiffies == 1) tick_nohz_stop_sched_tick() incorrectly assumes that the tick should not stop and takes an early exit and thus it won't update the load balancer cpu. Just afterwards the cpu will be killed and the load balancer cpu could be the offline cpu. On 2.6.32 based kernel get_nohz_load_balancer() gets called to decide on which cpu a timer should be enqueued (see __mod_timer()). Which leads to the possibility that timers get enqueued on an offline cpu. These will never expire and can cause a system hang. This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses get_nohz_timer_target() which doesn't have that problem. However there might be other problems because of the too early exit tick_nohz_stop_sched_tick() in case a cpu goes offline. The easiest and probably safest fix seems to be to let get_next_timer_interrupt() just lie and let it say there isn't any pending timer if the current cpu is offline. I also thought of moving migrate_[hr]timers() from CPU_DEAD to CPU_DYING, but seeing that there already have been fixes at least in the hrtimer code in this area I'm afraid that this could add new subtle bugs. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20101201091109.GA8984@osiris.boeblingen.de.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit dbd87b5af055a0cc9bba17795c9a2b0d17795389 upstream.

This fixes a bug as seen on 2.6.32 based kernels where timers got
enqueued on offline cpus.

If a cpu goes offline it might still have pending timers. These will
be migrated during CPU_DEAD handling after the cpu is offline.
However while the cpu is going offline it will schedule the idle task
which will then call tick_nohz_stop_sched_tick().

That function in turn will call get_next_timer_intterupt() to figure
out if the tick of the cpu can be stopped or not. If it turns out that
the next tick is just one jiffy off (delta_jiffies == 1)
tick_nohz_stop_sched_tick() incorrectly assumes that the tick should
not stop and takes an early exit and thus it won't update the load
balancer cpu.

Just afterwards the cpu will be killed and the load balancer cpu could
be the offline cpu.

On 2.6.32 based kernel get_nohz_load_balancer() gets called to decide
on which cpu a timer should be enqueued (see __mod_timer()). Which
leads to the possibility that timers get enqueued on an offline cpu.
These will never expire and can cause a system hang.

This has been observed 2.6.32 kernels. On current kernels
__mod_timer() uses get_nohz_timer_target() which doesn't have that
problem. However there might be other problems because of the too
early exit tick_nohz_stop_sched_tick() in case a cpu goes offline.

The easiest and probably safest fix seems to be to let
get_next_timer_interrupt() just lie and let it say there isn't any
pending timer if the current cpu is offline.

I also thought of moving migrate_[hr]timers() from CPU_DEAD to
CPU_DYING, but seeing that there already have been fixes at least in
the hrtimer code in this area I'm afraid that this could add new
subtle bugs.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101201091109.GA8984@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-23T16:46:15+00:00 Linus Torvalds torvalds@linux-foundation.org 2009-09-23T16:46:15+00:00 31bbb9b58d1e8ebcf2b28c95c2250a9f8e31e397 * 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: itimers: Add tracepoints for itimer hrtimer: Add tracepoint for hrtimers timers: Add tracepoints for timer_list timers cputime: Optimize jiffies_to_cputime(1) itimers: Simplify arm_timer() code a bit itimers: Fix periodic tics precision itimers: Merge ITIMER_VIRT and ITIMER_PROF Trivial header file include conflicts in kernel/fork.c 
* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  itimers: Add tracepoints for itimer
  hrtimer: Add tracepoint for hrtimers
  timers: Add tracepoints for timer_list timers
  cputime: Optimize jiffies_to_cputime(1)
  itimers: Simplify arm_timer() code a bit
  itimers: Fix periodic tics precision
  itimers: Merge ITIMER_VIRT and ITIMER_PROF

Trivial header file include conflicts in kernel/fork.c
perf: Do the big rename: Performance Counters -> Performance Events 2009-09-21T12:28:04+00:00 Ingo Molnar mingo@elte.hu 2009-09-21T10:02:48+00:00 cdd6c482c9ff9c55475ee7392ec8f672eddb7be6 Bye-bye Performance Counters, welcome Performance Events! In the past few months the perfcounters subsystem has grown out its initial role of counting hardware events, and has become (and is becoming) a much broader generic event enumeration, reporting, logging, monitoring, analysis facility. Naming its core object 'perf_counter' and naming the subsystem 'perfcounters' has become more and more of a misnomer. With pending code like hw-breakpoints support the 'counter' name is less and less appropriate. All in one, we've decided to rename the subsystem to 'performance events' and to propagate this rename through all fields, variables and API names. (in an ABI compatible fashion) The word 'event' is also a bit shorter than 'counter' - which makes it slightly more convenient to write/handle as well. Thanks goes to Stephane Eranian who first observed this misnomer and suggested a rename. User-space tooling and ABI compatibility is not affected - this patch should be function-invariant. (Also, defconfigs were not touched to keep the size down.) This patch has been generated via the following script: FILES=$(find * -type f | grep -vE 'oprofile|[^K]config') sed -i \ -e 's/PERF_EVENT_/PERF_RECORD_/g' \ -e 's/PERF_COUNTER/PERF_EVENT/g' \ -e 's/perf_counter/perf_event/g' \ -e 's/nb_counters/nb_events/g' \ -e 's/swcounter/swevent/g' \ -e 's/tpcounter_event/tp_event/g' \ $FILES for N in $(find . -name perf_counter.[ch]); do M=$(echo $N | sed 's/perf_counter/perf_event/g') mv $N $M done FILES=$(find . -name perf_event.*) sed -i \ -e 's/COUNTER_MASK/REG_MASK/g' \ -e 's/COUNTER/EVENT/g' \ -e 's/\<event\>/event_id/g' \ -e 's/counter/event/g' \ -e 's/Counter/Event/g' \ $FILES ... to keep it as correct as possible. This script can also be used by anyone who has pending perfcounters patches - it converts a Linux kernel tree over to the new naming. We tried to time this change to the point in time where the amount of pending patches is the smallest: the end of the merge window. Namespace clashes were fixed up in a preparatory patch - and some stylistic fallout will be fixed up in a subsequent patch. ( NOTE: 'counters' are still the proper terminology when we deal with hardware registers - and these sed scripts are a bit over-eager in renaming them. I've undone some of that, but in case there's something left where 'counter' would be better than 'event' we can undo that on an individual basis instead of touching an otherwise nicely automated patch. ) Suggested-by: Stephane Eranian <eranian@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Paul Mackerras <paulus@samba.org> Reviewed-by: Arjan van de Ven <arjan@linux.intel.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Howells <dhowells@redhat.com> Cc: Kyle McMartin <kyle@mcmartin.ca> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: <linux-arch@vger.kernel.org> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> 
Bye-bye Performance Counters, welcome Performance Events!

In the past few months the perfcounters subsystem has grown out its
initial role of counting hardware events, and has become (and is
becoming) a much broader generic event enumeration, reporting, logging,
monitoring, analysis facility.

Naming its core object 'perf_counter' and naming the subsystem
'perfcounters' has become more and more of a misnomer. With pending
code like hw-breakpoints support the 'counter' name is less and
less appropriate.

All in one, we've decided to rename the subsystem to 'performance
events' and to propagate this rename through all fields, variables
and API names. (in an ABI compatible fashion)

The word 'event' is also a bit shorter than 'counter' - which makes
it slightly more convenient to write/handle as well.

Thanks goes to Stephane Eranian who first observed this misnomer and
suggested a rename.

User-space tooling and ABI compatibility is not affected - this patch
should be function-invariant. (Also, defconfigs were not touched to
keep the size down.)

This patch has been generated via the following script:

  FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')

  sed -i \
    -e 's/PERF_EVENT_/PERF_RECORD_/g' \
    -e 's/PERF_COUNTER/PERF_EVENT/g' \
    -e 's/perf_counter/perf_event/g' \
    -e 's/nb_counters/nb_events/g' \
    -e 's/swcounter/swevent/g' \
    -e 's/tpcounter_event/tp_event/g' \
    $FILES

  for N in $(find . -name perf_counter.[ch]); do
    M=$(echo $N | sed 's/perf_counter/perf_event/g')
    mv $N $M
  done

  FILES=$(find . -name perf_event.*)

  sed -i \
    -e 's/COUNTER_MASK/REG_MASK/g' \
    -e 's/COUNTER/EVENT/g' \
    -e 's/\<event\>/event_id/g' \
    -e 's/counter/event/g' \
    -e 's/Counter/Event/g' \
    $FILES

... to keep it as correct as possible. This script can also be
used by anyone who has pending perfcounters patches - it converts
a Linux kernel tree over to the new naming. We tried to time this
change to the point in time where the amount of pending patches
is the smallest: the end of the merge window.

Namespace clashes were fixed up in a preparatory patch - and some
stylistic fallout will be fixed up in a subsequent patch.

( NOTE: 'counters' are still the proper terminology when we deal
  with hardware registers - and these sed scripts are a bit
  over-eager in renaming them. I've undone some of that, but
  in case there's something left where 'counter' would be
  better than 'event' we can undo that on an individual basis
  instead of touching an otherwise nicely automated patch. )

Suggested-by: Stephane Eranian <eranian@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-arch@vger.kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-18T16:15:24+00:00 Linus Torvalds torvalds@linux-foundation.org 2009-09-18T16:15:24+00:00 a03fdb7612874834d6847107198712d18b5242c7 * '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. 
* '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.
timers: Add tracepoints for timer_list timers 2009-08-29T12:10:06+00:00 Xiao Guangrong xiaoguangrong@cn.fujitsu.com 2009-08-10T02:48:59+00:00 2b022e3d4bf9885f781221c59d86283a2cdfc2ed Add tracepoints which cover the timer life cycle. The tracepoints are integrated with the already existing debug_object debug points as far as possible. Based on patches from Mathieu: http://marc.info/?l=linux-kernel&m=123791201816247&w=2 and Anton: http://marc.info/?l=linux-kernel&m=124331396919301&w=2 [ tglx: Fixed timeout value in timer_start tracepoint, massaged comments and made the printk's more readable ] Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Cc: Anton Blanchard <anton@samba.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Peter Zijlstra <peterz@infradead.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Zhaolei <zhaolei@cn.fujitsu.com> LKML-Reference: <4A7F8A9B.3040201@cn.fujitsu.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 
Add tracepoints which cover the timer life cycle. The tracepoints are
integrated with the already existing debug_object debug points as far
as possible.

Based on patches from 
Mathieu: http://marc.info/?l=linux-kernel&m=123791201816247&w=2
and 
Anton: http://marc.info/?l=linux-kernel&m=124331396919301&w=2

[ tglx: Fixed timeout value in timer_start tracepoint, massaged
  comments and made the printk's more readable ]

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
LKML-Reference: <4A7F8A9B.3040201@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
timer.c: Fix S/390 comments 2009-08-26T06:07:31+00:00 Randy Dunlap randy.dunlap@oracle.com 2009-08-25T21:35:41+00:00 90cba64a5f672a239f43ec5cb9a11b806887331e Fix typos and add omitted words. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: akpm <akpm@linux-foundation.org> Cc: linux390@de.ibm.com Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> LKML-Reference: <20090825143541.43fc2ed8.randy.dunlap@oracle.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> 
Fix typos and add omitted words.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: akpm <akpm@linux-foundation.org>
Cc: linux390@de.ibm.com
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
LKML-Reference: <20090825143541.43fc2ed8.randy.dunlap@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
rcu: Simplify rcu_pending()/rcu_check_callbacks() API 2009-08-23T08:32:39+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2009-08-22T20:56:51+00:00 a157229cabd6dd8cfa82525fc9bf730c94cc9ac2 All calls from outside RCU are of the form: if (rcu_pending(cpu)) rcu_check_callbacks(cpu, user); This is silly, instead we put a call to rcu_pending() in rcu_check_callbacks(), and then make the outside calls be to rcu_check_callbacks(). This cuts down on the code a bit and also gives the compiler a better chance of optimizing. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <125097461311-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu> 
All calls from outside RCU are of the form:

	if (rcu_pending(cpu))
		rcu_check_callbacks(cpu, user);

This is silly, instead we put a call to rcu_pending() in
rcu_check_callbacks(), and then make the outside calls be to
rcu_check_callbacks().  This cuts down on the code a bit and
also gives the compiler a better chance of optimizing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josht@linux.vnet.ibm.com
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
LKML-Reference: <125097461311-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Merge branch 'linus' into timers/core 2009-08-14T13:59:30+00:00 Thomas Gleixner tglx@linutronix.de 2009-08-14T13:59:00+00:00 4cd1993f0046fbc765dbf20af90966f5661e3789 Reason: Martin's timekeeping cleanup series depends on both timers/core and mainline changes. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 
Reason: Martin's timekeeping cleanup series depends on both
timers/core and mainline changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
timers: Cache __next_timer_interrupt result 2009-08-04T18:28:25+00:00 Martin Schwidefsky schwidefsky@de.ibm.com 2009-07-21T18:25:05+00:00 97fd9ed48ce2b807edc363bef3e817aeeb5cd5e6 Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is searched for the next timer interrupt. It can take quite a few cycles to find the next pending timer. This patch adds a field to tvec_base that caches the result of __next_timer_interrupt. The hit ratio is around 80% on my thinkpad under normal use, on a server I've seen hit ratios from 5% to 95% dependent on the workload. -v2: jiffies wrap fixes Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: john stultz <johnstul@us.ibm.com> Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com> LKML-Reference: <20090721202505.7d56a079@skybase> Signed-off-by: Ingo Molnar <mingo@elte.hu> 
Each time a cpu goes to sleep on a NOHZ=y system the timer
wheel is searched for the next timer interrupt. It can take
quite a few cycles to find the next pending timer.

This patch adds a field to tvec_base that caches the result of
__next_timer_interrupt.

The hit ratio is around 80% on my thinkpad under normal use, on
a server I've seen hit ratios from 5% to 95% dependent on the
workload.

-v2: jiffies wrap fixes

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20090721202505.7d56a079@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
timer: Avoid reading uninitialized data 2009-07-18T21:11:43+00:00 Pavel Roskin proski@gnu.org 2009-07-18T20:46:02+00:00 4841158b26e28e1476eed84c7347c18f11317750 timer->expires may be uninitialized, so check timer_pending() before touching timer->expires to pacify kmemcheck. Signed-off-by: Pavel Roskin <proski@gnu.org> LKML-Reference: <20090718204602.5191.360.stgit@mj.roinet.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 
timer->expires may be uninitialized, so check timer_pending() before
touching timer->expires to pacify kmemcheck.

Signed-off-by: Pavel Roskin <proski@gnu.org>
LKML-Reference: <20090718204602.5191.360.stgit@mj.roinet.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>