15 Oct, 2014
1 commit
-
Pull percpu consistent-ops changes from Tejun Heo:
"Way back, before the current percpu allocator was implemented, static
and dynamic percpu memory areas were allocated and handled separately
and had their own accessors. The distinction has been gone for many
years now; however, the now duplicate two sets of accessors remained
with the pointer based ones - this_cpu_*() - evolving various other
operations over time. During the process, we also accumulated other
inconsistent operations.This pull request contains Christoph's patches to clean up the
duplicate accessor situation. __get_cpu_var() uses are replaced with
with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr().Unfortunately, the former sometimes is tricky thanks to C being a bit
messy with the distinction between lvalues and pointers, which led to
a rather ugly solution for cpumask_var_t involving the introduction of
this_cpu_cpumask_var_ptr().This converts most of the uses but not all. Christoph will follow up
with the remaining conversions in this merge window and hopefully
remove the obsolete accessors"* 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits)
irqchip: Properly fetch the per cpu offset
percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix
ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write.
percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t
Revert "powerpc: Replace __get_cpu_var uses"
percpu: Remove __this_cpu_ptr
clocksource: Replace __this_cpu_ptr with raw_cpu_ptr
sparc: Replace __get_cpu_var uses
avr32: Replace __get_cpu_var with __this_cpu_write
blackfin: Replace __get_cpu_var uses
tile: Use this_cpu_ptr() for hardware counters
tile: Replace __get_cpu_var uses
powerpc: Replace __get_cpu_var uses
alpha: Replace __get_cpu_var
ia64: Replace __get_cpu_var uses
s390: cio driver &__get_cpu_var replacements
s390: Replace __get_cpu_var uses
mips: Replace __get_cpu_var uses
MIPS: Replace __get_cpu_var uses in FPU emulator.
arm: Replace __this_cpu_ptr with raw_cpu_ptr
...
14 Sep, 2014
1 commit
-
This way we unbloat a bit main.c and more importantly we initialize
nohz full after init_IRQ(). This dependency will be needed in further
patches because nohz full needs irq work to raise its own IRQ.
Information about the support for this ability on ARM64 is obtained on
init_IRQ() which initialize the pointer to __smp_call_function.Since tick_init() is called right after init_IRQ(), this is a good place
to call tick_nohz_init() and prepare for that dependency.Acked-by: Peter Zijlstra (Intel)
Cc: Ingo Molnar
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Frederic Weisbecker
27 Aug, 2014
1 commit
-
Convert uses of __get_cpu_var for creating a address from a percpu
offset to this_cpu_ptr.The two cases where get_cpu_var is used to actually access a percpu
variable are changed to use this_cpu_read/raw_cpu_read.Reviewed-by: Thomas Gleixner
Signed-off-by: Christoph Lameter
Signed-off-by: Tejun Heo
16 Apr, 2014
1 commit
-
tick_check_replacement() returns if a replacement of clock_event_device is
possible or not. It does this as the first check:if (tick_check_percpu(curdev, newdev, smp_processor_id()))
return false;Thats wrong. tick_check_percpu() returns true when the device is
useable. Check for false instead.[ tglx: Massaged changelog ]
Signed-off-by: Viresh Kumar
Cc: # v3.11+
Cc: linaro-kernel@lists.linaro.org
Cc: fweisbec@gmail.com
Cc: Arvind.Chauhan@arm.com
Cc: linaro-networking@linaro.org
Link: http://lkml.kernel.org/r/486a02efe0246635aaba786e24b42d316438bf3b.1397537987.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner
26 Mar, 2014
2 commits
-
tick_handle_periodic() is calling ktime_add() at two places, first before the
infinite loop and then at the end of infinite loop. We can rearrange code a bit
to fix code duplication here.It looks quite simple and shouldn't break anything, I guess :)
Signed-off-by: Viresh Kumar
Cc: linaro-kernel@lists.linaro.org
Cc: fweisbec@gmail.com
Link: http://lkml.kernel.org/r/be3481e8f3f71df694a4b43623254fc93ca51b59.1395735873.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner -
One of the comments in tick_handle_periodic() had 'when' instead of 'which' (My
guess :)). Fix it.Also fix spelling mistake in 'Possible'.
Signed-off-by: Viresh Kumar
Cc: linaro-kernel@lists.linaro.org
Cc: skarafotis@gmail.com
Link: http://lkml.kernel.org/r/2b29ca4230c163e44179941d7c7a16c1474385c2.1395743878.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner
12 Jan, 2014
1 commit
-
Pull timekeeping updates from John Stultz.
Signed-off-by: Ingo Molnar
24 Dec, 2013
1 commit
-
Since the xtime lock was split into the timekeeping lock and
the jiffies lock, we no longer need to call update_wall_time()
while holding the jiffies lock.Thus, this patch splits update_wall_time() out from do_timer().
This allows us to get away from calling clock_was_set_delayed()
in update_wall_time() and instead use the standard clock_was_set()
call that previously would deadlock, as it causes the jiffies lock
to be acquired.Cc: Sasha Levin
Cc: Thomas Gleixner
Cc: Prarit Bhargava
Cc: Richard Cochran
Cc: Ingo Molnar
Signed-off-by: John Stultz
19 Nov, 2013
1 commit
-
Taken straight from a tglx email ;)
Signed-off-by: Andrew Morton
Signed-off-by: Thomas Gleixner
02 Jul, 2013
1 commit
-
The recent implementation of a generic dummy timer resulted in a
different registration order of per cpu local timers which made the
broadcast control logic go belly up.If the dummy timer is the first clock event device which is registered
for a CPU, then it is installed, the broadcast timer is initialized
and the CPU is marked as broadcast target.If a real clock event device is installed after that, we can fail to
take the CPU out of the broadcast mask. In the worst case we end up
with two periodic timer events firing for the same CPU. One from the
per cpu hardware device and one from the broadcast.Now the problem is that we have no way to distinguish whether the
system is in a state which makes broadcasting necessary or the
broadcast bit was set due to the nonfunctional dummy timer
installment.To solve this we need to keep track of the system state seperately and
provide a more detailed decision logic whether we keep the CPU in
broadcast mode or not.The old decision logic only clears the broadcast mode, if the newly
installed clock event device is not affected by power states.The new logic clears the broadcast mode if one of the following is
true:- The new device is not affected by power states.
- The system is not in a power state affected mode
- The system has switched to oneshot mode. The oneshot broadcast is
controlled from the deep idle state. The CPU is not in idle at
this point, so it's safe to remove it from the mask.If we clear the broadcast bit for the CPU when a new device is
installed, we also shutdown the broadcast device when this was the
last CPU in the broadcast mask.If the broadcast bit is kept, then we leave the new device in shutdown
state and rely on the broadcast to deliver the timer interrupts via
the broadcast ipis.Reported-and-tested-by: Stehle Vincent-B46079
Reviewed-by: Stephen Boyd
Cc: John Stultz ,
Cc: Mark Rutland
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307012153060.4013@ionos.tec.linutronix.de
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner
25 Jun, 2013
1 commit
-
On an SMP system with only one global clockevent and a dummy
clockevent per CPU we run into problems. We want the dummy
clockevents to be registered as the per CPU tick devices, but
we can only achieve that if we register the dummy clockevents
before the global clockevent or if we artificially inflate the
rating of the dummy clockevents to be higher than the rating
of the global clockevent. Failure to do so leads to boot
hangs when the dummy timers are registered on all other CPUs
besides the CPU that accepted the global clockevent as its tick
device and there is no broadcast timer to poke the dummy
devices.If we're registering multiple clockevents and one clockevent is
global and the other is local to a particular CPU we should
choose to use the local clockevent regardless of the rating of
the device. This way, if the clockevent is a dummy it will take
the tick device duty as long as there isn't a higher rated tick
device and any global clockevent will be bumped out into
broadcast mode, fixing the problem described above.Reported-and-tested-by: Mark Rutland
Signed-off-by: Stephen Boyd
Tested-by: soren.brinkmann@xilinx.com
Cc: John Stultz
Cc: Daniel Lezcano
Cc: linux-arm-kernel@lists.infradead.org
Cc: John Stultz
Link: http://lkml.kernel.org/r/20130613183950.GA32061@codeaurora.org
Signed-off-by: Thomas Gleixner
16 May, 2013
6 commits
-
Provide a sysfs interface to allow unbinding of clockevent
devices. The device is unbound if it is unused or if there is a
replacement device available. Unbinding of broadcast devices is not
supported as we don't want to foster that nonsense. If no replacement
device is available the unbind returns -EBUSY. Unbind is available
from the kernel and through sysfs, which is necessary to drop the
module refcount.Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.499216659@linutronix.de
Signed-off-by: Thomas Gleixner -
Split out the clockevent device selection logic. Preparatory patch to
allow unbinding active clockevent devices.Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.431796247@linutronix.de
Signed-off-by: Thomas Gleixner -
We want to be able to remove clockevent modules as well. Add a
refcount so we don't remove a module with an active clock event
device.Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.307435149@linutronix.de
Signed-off-by: Thomas Gleixner -
No need to call another function and have duplicated cases.
Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.235746557@linutronix.de
Signed-off-by: Thomas Gleixner -
Now that the notifier chain is gone there are no other users and it's
pointless to nest tick_device_lock inside of clockevents_lock because
there is no other use case.Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.162888472@linutronix.de
Signed-off-by: Thomas Gleixner -
7+ years and still a single user. Kill it.
Signed-off-by: Thomas Gleixner
Cc: John Stultz
Cc: Magnus Damm
Link: http://lkml.kernel.org/r/20130425143436.098520211@linutronix.de
Signed-off-by: Thomas Gleixner
06 May, 2013
1 commit
-
Pull 'full dynticks' support from Ingo Molnar:
"This tree from Frederic Weisbecker adds a new, (exciting! :-) core
kernel feature to the timer and scheduler subsystems: 'full dynticks',
or CONFIG_NO_HZ_FULL=y.This feature extends the nohz variable-size timer tick feature from
idle to busy CPUs (running at most one task) as well, potentially
reducing the number of timer interrupts significantly.This feature got motivated by real-time folks and the -rt tree, but
the general utility and motivation of full-dynticks runs wider than
that:- HPC workloads get faster: CPUs running a single task should be able
to utilize a maximum amount of CPU power. A periodic timer tick at
HZ=1000 can cause a constant overhead of up to 1.0%. This feature
removes that overhead - and speeds up the system by 0.5%-1.0% on
typical distro configs even on modern systems.- Real-time workload latency reduction: CPUs running critical tasks
should experience as little jitter as possible. The last remaining
source of kernel-related jitter was the periodic timer tick.- A single task executing on a CPU is a pretty common situation,
especially with an increasing number of cores/CPUs, so this feature
helps desktop and mobile workloads as well.The cost of the feature is mainly related to increased timer
reprogramming overhead when a CPU switches its tick period, and thus
slightly longer to-idle and from-idle latency.Configuration-wise a third mode of operation is added to the existing
two NOHZ kconfig modes:- CONFIG_HZ_PERIODIC: [formerly !CONFIG_NO_HZ], now explicitly named
as a config option. This is the traditional Linux periodic tick
design: there's a HZ tick going on all the time, regardless of
whether a CPU is idle or not.- CONFIG_NO_HZ_IDLE: [formerly CONFIG_NO_HZ=y], this turns off the
periodic tick when a CPU enters idle mode.- CONFIG_NO_HZ_FULL: this new mode, in addition to turning off the
tick when a CPU is idle, also slows the tick down to 1 Hz (one
timer interrupt per second) when only a single task is running on a
CPU.The .config behavior is compatible: existing !CONFIG_NO_HZ and
CONFIG_NO_HZ=y settings get translated to the new values, without the
user having to configure anything. CONFIG_NO_HZ_FULL is turned off by
default.This feature is based on a lot of infrastructure work that has been
steadily going upstream in the last 2-3 cycles: related RCU support
and non-periodic cputime support in particular is upstream already.This tree adds the final pieces and activates the feature. The pull
request is marked RFC because:- it's marked 64-bit only at the moment - the 32-bit support patch is
small but did not get ready in time.- it has a number of fresh commits that came in after the merge
window. The overwhelming majority of commits are from before the
merge window, but still some aspects of the tree are fresh and so I
marked it RFC.- it's a pretty wide-reaching feature with lots of effects - and
while the components have been in testing for some time, the full
combination is still not very widely used. That it's default-off
should reduce its regression abilities and obviously there are no
known regressions with CONFIG_NO_HZ_FULL=y enabled either.- the feature is not completely idempotent: there is no 100%
equivalent replacement for a periodic scheduler/timer tick. In
particular there's ongoing work to map out and reduce its effects
on scheduler load-balancing and statistics. This should not impact
correctness though, there are no known regressions related to this
feature at this point.- it's a pretty ambitious feature that with time will likely be
enabled by most Linux distros, and we'd like you to make input on
its design/implementation, if you dislike some aspect we missed.
Without flaming us to crisp! :-)Future plans:
- there's ongoing work to reduce 1Hz to 0Hz, to essentially shut off
the periodic tick altogether when there's a single busy task on a
CPU. We'd first like 1 Hz to be exposed more widely before we go
for the 0 Hz target though.- once we reach 0 Hz we can remove the periodic tick assumption from
nr_running>=2 as well, by essentially interrupting busy tasks only
as frequently as the sched_latency constraints require us to do -
once every 4-40 msecs, depending on nr_running.I am personally leaning towards biting the bullet and doing this in
v3.10, like the -rt tree this effort has been going on for too long -
but the final word is up to you as usual.More technical details can be found in Documentation/timers/NO_HZ.txt"
* 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
sched: Keep at least 1 tick per second for active dynticks tasks
rcu: Fix full dynticks' dependency on wide RCU nocb mode
nohz: Protect smp_processor_id() in tick_nohz_task_switch()
nohz_full: Add documentation.
cputime_nsecs: use math64.h for nsec resolution conversion helpers
nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config
nohz: Reduce overhead under high-freq idling patterns
nohz: Remove full dynticks' superfluous dependency on RCU tree
nohz: Fix unavailable tick_stop tracepoint in dynticks idle
nohz: Add basic tracing
nohz: Select wide RCU nocb for full dynticks
nohz: Disable the tick when irq resume in full dynticks CPU
nohz: Re-evaluate the tick for the new task after a context switch
nohz: Prepare to stop the tick on irq exit
nohz: Implement full dynticks kick
nohz: Re-evaluate the tick from the scheduler IPI
sched: New helper to prevent from stopping the tick in full dynticks
sched: Kick full dynticks CPU that have more than one task enqueued.
perf: New helper to prevent full dynticks CPUs from stopping tick
perf: Kick full dynticks CPU if events rotation is needed
...
25 Apr, 2013
1 commit
-
Vitaliy reported that a per cpu HPET timer interrupt crashes the
system during hibernation. What happens is that the per cpu HPET timer
gets shut down when the nonboot cpus are stopped. When the nonboot
cpus are onlined again the HPET code sets up the MSI interrupt which
fires before the clock event device is registered. The event handler
is still set to hrtimer_interrupt, which then crashes the machine due
to highres mode not being active.See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=700333
There is no real good way to avoid that in the HPET code. The HPET
code alrady has a mechanism to detect spurious interrupts when event
handler == NULL for a similar reason.We can handle that in the clockevent/tick layer and replace the
previous functional handler with a dummy handler like we do in
tick_setup_new_device().The original clockevents code did this in clockevents_exchange_device(),
but that got removed by commit 7c1e76897 (clockevents: prevent
clockevent event_handler ending up handler_noop) which forgot to fix
it up in tick_shutdown(). Same issue with the broadcast device.Reported-by: Vitaliy Fillipov
Cc: Ben Hutchings
Cc: stable@vger.kernel.org
Cc: 700333@bugs.debian.org
Signed-off-by: Thomas Gleixner
16 Apr, 2013
1 commit
-
"Extended nohz" was used as a naming base for the full dynticks
API and Kconfig symbols. It reflects the fact the system tries
to stop the tick in more places than just idle.But that "extended" name is a bit opaque and vague. Rename it to
"full" makes it clearer what the system tries to do under this
config: try to shutdown the tick anytime it can. The various
constraints that prevent that to happen shouldn't be considered
as fundamental properties of this feature but rather technical
issues that may be solved in the future.Reported-by: Ingo Molnar
Signed-off-by: Frederic Weisbecker
Cc: Chris Metcalf
Cc: Christoph Lameter
Cc: Geoff Levand
Cc: Gilad Ben Yossef
Cc: Hakan Akkan
Cc: Ingo Molnar
Cc: Kevin Hilman
Cc: Li Zhong
Cc: Paul E. McKenney
Cc: Paul Gortmaker
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
21 Mar, 2013
1 commit
-
This way the full nohz CPUs can safely run with the tick
stopped with a guarantee that somebody else is taking
care of the jiffies and GTOD progression.Once the duty is attributed to a CPU, it won't change. Also that
CPU can't enter into dyntick idle mode or be hot unplugged.This may later be improved from a power consumption POV. At
least we should be able to share the duty amongst all CPUs
outside the full dynticks range. Then the duty could even be
shared with full dynticks CPUs when those can't stop their
tick for any reason.But let's start with that very simple approach first.
Signed-off-by: Frederic Weisbecker
Cc: Andrew Morton
Cc: Chris Metcalf
Cc: Christoph Lameter
Cc: Geoff Levand
Cc: Gilad Ben Yossef
Cc: Hakan Akkan
Cc: Ingo Molnar
Cc: Kevin Hilman
Cc: Li Zhong
Cc: Namhyung Kim
Cc: Paul E. McKenney
Cc: Paul Gortmaker
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
[fix have_nohz_full_mask offcase]
Signed-off-by: Steven Rostedt
07 Mar, 2013
1 commit
-
Signed-off-by: Thomas Gleixner
Link: http://lkml.kernel.org/r/20130306111537.366394000@linutronix.de
Cc: Rusty Russell
14 Nov, 2012
1 commit
-
Now that timekeeping is protected by its own locks, rename
the xtime_lock to jifffies_lock to better describe what it
protects.CC: Thomas Gleixner
CC: Eric Dumazet
CC: Richard Cochran
Signed-off-by: John Stultz
08 Sep, 2011
1 commit
-
The automatic increase of the min_delta_ns of a clockevents device
should be done in the clockevents code as the minimum delay is an
attribute of the clockevents device.In addition not all architectures want the automatic adjustment, on a
massively virtualized system it can happen that the programming of a
clock event fails several times in a row because the virtual cpu has
been rescheduled quickly enough. In that case the minimum delay will
erroneously be increased with no way back. The new config symbol
GENERIC_CLOCKEVENTS_MIN_ADJUST is used to enable the automatic
adjustment. The config option is selected only for x86.Signed-off-by: Martin Schwidefsky
Cc: john stultz
Link: http://lkml.kernel.org/r/20110823133142.494157493@de.ibm.com
Signed-off-by: Thomas Gleixner
16 Mar, 2011
1 commit
-
…l/git/tip/linux-2.6-tip
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (62 commits)
posix-clocks: Check write permissions in posix syscalls
hrtimer: Remove empty hrtimer_init_hres_timer()
hrtimer: Update hrtimer->state documentation
hrtimer: Update base[CLOCK_BOOTTIME].offset correctly
timers: Export CLOCK_BOOTTIME via the posix timers interface
timers: Add CLOCK_BOOTTIME hrtimer base
time: Extend get_xtime_and_monotonic_offset() to also return sleep
time: Introduce get_monotonic_boottime and ktime_get_boottime
hrtimers: extend hrtimer base code to handle more then 2 clockids
ntp: Remove redundant and incorrect parameter check
mn10300: Switch do_timer() to xtimer_update()
posix clocks: Introduce dynamic clocks
posix-timers: Cleanup namespace
posix-timers: Add support for fd based clocks
x86: Add clock_adjtime for x86
posix-timers: Introduce a syscall for clock tuning.
time: Splitout compat timex accessors
ntp: Add ADJ_SETOFFSET mode bit
time: Introduce timekeeping_inject_offset
posix-timer: Update comment
...Fix up new system-call-related conflicts in
arch/x86/ia32/ia32entry.S
arch/x86/include/asm/unistd_32.h
arch/x86/include/asm/unistd_64.h
arch/x86/kernel/syscall_table_32.S
(name_to_handle_at()/open_by_handle_at() vs clock_adjtime()), and some
due to movement of get_jiffies_64() in:
kernel/time.c
26 Feb, 2011
1 commit
-
When the per cpu timer is marked CLOCK_EVT_FEAT_C3STOP, then we only
can switch into oneshot mode, when the backup broadcast device
supports oneshot mode as well. Otherwise we would try to switch the
broadcast device into an unsupported mode unconditionally. This went
unnoticed so far as the current available broadcast devices support
oneshot mode. Seth unearthed this problem while debugging and working
around an hpet related BIOS wreckage.Add the necessary check to tick_is_oneshot_available().
Reported-and-tested-by: Seth Forshee
Signed-off-by: Thomas Gleixner
LKML-Reference:
Cc: stable@kernel.org # .21 ->
01 Feb, 2011
1 commit
-
All callers of do_timer() are converted to xtime_update(). The only
users of xtime_lock are in kernel/time/. Make both local to
kernel/time/ and remove them from the global header files.[ tglx: Reuse tick-internal.h instead of creating another local header
file. Massaged changelog ]Signed-off-by: Torben Hohn
Cc: Peter Zijlstra
Cc: johnstul@us.ibm.com
Cc: yong.zhang0@gmail.com
Cc: hch@infradead.org
Signed-off-by: Thomas Gleixner
17 Dec, 2010
1 commit
-
__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes). Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.Cc: Pekka Enberg
Cc: Hugh Dickins
Cc: Thomas Gleixner
Acked-by: H. Peter Anvin
Signed-off-by: Christoph Lameter
Signed-off-by: Tejun Heo
15 Dec, 2009
2 commits
-
Convert locks which cannot be sleeping locks in preempt-rt to
raw_spinlocks.Signed-off-by: Thomas Gleixner
Acked-by: Peter Zijlstra
Acked-by: Ingo Molnar -
Signed-off-by: Thomas Gleixner
Acked-by: Peter Zijlstra
Acked-by: Ingo Molnar
02 May, 2009
1 commit
-
tick_handle_periodic() can lock up hard when a one shot clock event
device is used in combination with jiffies clocksource.Avoid an endless loop issue by requiring that a highres valid
clocksource be installed before we call tick_periodic() in a loop when
using ONESHOT mode. The result is we will only increment jiffies once
per interrupt until a continuous hardware clocksource is available.Without this, we can run into a endless loop, where each cycle through
the loop, jiffies is updated which increments time by tick_period or
more (due to clock steering), which can cause the event programming to
think the next event was before the newly incremented time and fail
causing tick_periodic() to be called again and the whole process loops
forever.[ Impact: prevent hard lock up ]
Signed-off-by: John Stultz
Signed-off-by: Andrew Morton
Signed-off-by: Thomas Gleixner
Cc: stable@kernel.org
31 Jan, 2009
1 commit
-
Impact: fix CPU hotplug hang on Power6 testbox
On architectures that support offlining all cpus (at least powerpc/pseries),
hot-unpluging the tick_do_timer_cpu can result in a system hang.This comes from the fact that if the cpu going down happens to be the
cpu doing the tick, then as the tick_do_timer_cpu handover happens after the
cpu is dead (via the CPU_DEAD notification), we're left without ticks,
jiffies are frozen and any task relying on timers (msleep, ...) is stuck.
That's particularly the case for the cpu looping in __cpu_die() waiting
for the dying cpu to be dead.This patch addresses this by having the tick_do_timer_cpu handover happen
earlier during the CPU_DYING notification. For this, a new clockevent
notification type is introduced (CLOCK_EVT_NOTIFY_CPU_DYING) which is triggered
in hrtimer_cpu_notify().Signed-off-by: Sebastien Dugue
Cc:
Signed-off-by: Ingo Molnar
01 Jan, 2009
1 commit
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Impact: Use new APIs
Convert kernel/time functions to use struct cpumask *.
Note the ugly bitmap declarations in tick-broadcast.c. These should
be cpumask_var_t, but there was no obvious initialization function to
put the alloc_cpumask_var() calls in. This was safe.(Eventually 'struct cpumask' will be undefined for CONFIG_CPUMASK_OFFSTACK,
so we use a bitmap here to show we really mean it).Signed-off-by: Rusty Russell
Signed-off-by: Mike Travis
13 Dec, 2008
2 commits
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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
Cc: Ingo Molnar -
Impact: change existing irq_chip API
Not much point with gentle transition here: the struct irq_chip's
setaffinity method signature needs to change.Fortunately, not widely used code, but hits a few architectures.
Note: In irq_select_affinity() I save a temporary in by mangling
irq_desc[irq].affinity directly. Ingo, does this break anything?(Folded in fix from KOSAKI Motohiro)
Signed-off-by: Rusty Russell
Signed-off-by: Mike Travis
Reviewed-by: Grant Grundler
Acked-by: Ingo Molnar
Cc: ralf@linux-mips.org
Cc: grundler@parisc-linux.org
Cc: jeremy@xensource.com
Cc: KOSAKI Motohiro
23 Sep, 2008
2 commits
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Impact: timer hang on CPU online observed on AMD C1E systems
When a CPU is brought online then the broadcast machinery can
be in the one shot state already. Check this and setup the timer
device of the new CPU in one shot mode so the broadcast code
can pick up the next_event value correctly.Another AMD C1E oddity, as we switch to broadcast immediately and
not after the full bring up via the ACPI cpu idle code.Signed-off-by: Thomas Gleixner
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Impact: rare hang which can be triggered on CPU online.
tick_do_timer_cpu keeps track of the CPU which updates jiffies
via do_timer. The value -1 is used to signal, that currently no
CPU is doing this. There are two cases, where the variable can
have this state:boot:
necessary for systems where the boot cpu id can be != 0nohz long idle sleep:
When the CPU which did the jiffies update last goes into
a long idle sleep it drops the update jiffies duty so
another CPU which is not idle can pick it up and keep
jiffies going.Using the same value for both situations is wrong, as the CPU online
code can see the -1 state when the timer of the newly onlined CPU is
setup. The setup for a newly onlined CPU goes through periodic mode
and can pick up the do_timer duty without being aware of the nohz /
highres mode of the already running system.Use two separate states and make them constants to avoid magic
numbers confusion.Signed-off-by: Thomas Gleixner
17 Sep, 2008
1 commit
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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
05 Sep, 2008
1 commit
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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
Signed-off-by: Shaohua Li
Signed-off-by: Thomas Gleixner
Signed-off-by: Ingo Molnar
26 Jul, 2008
1 commit
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* Replace previous instances of the cpumask_of_cpu_ptr* macros
with a the new (lvalue capable) generic cpumask_of_cpu().Signed-off-by: Mike Travis
Cc: Andrew Morton
Cc: Jack Steiner
Cc: Rusty Russell
Signed-off-by: Ingo Molnar
