While playing around with it, I noticed we missed some sanity checks.
Also add some comments while we're there.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should not only correct the increment for the initial group, but should
be consistent and do so for all the groups we encounter.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Rework the wakeup preemption to work on real runtime instead of
the virtual runtime. This greatly simplifies the code.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
- Add some comments to try to make the ifdef puzzle a bit clearer
- Explicitly inline one of the three init_hrtick() implementations.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LD kernel/built-in.o
WARNING: kernel/built-in.o(.text+0x326): Section mismatch in reference
from the function init_hrtick() to the variable
.cpuinit.data:hotplug_hrtick_nb.8
The function init_hrtick() references
the variable __cpuinitdata hotplug_hrtick_nb.8.
This is often because init_hrtick lacks a __cpuinitdata
annotation or the annotation of hotplug_hrtick_nb.8 is wrong.
Signed-off-by: Md.Rakib H. Mullick <rakib.mullick@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
load_balance_fair() calls rcu_read_lock() but then traverses the list
using the regular list traversal routine. This patch converts the
list traversal to use the _rcu version.
Signed-off-by: Chris Friesen <cfriesen@nortel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Lin Ming reported a 10% OLTP regression against 2.6.27-rc4.
The difference seems to come from different preemption agressiveness,
which affects the cache footprint of the workload and its effective
cache trashing.
Aggresively preempt a task if its avg overlap is very small, this should
avoid the task going to sleep and find it still running when we schedule
back to it - saving a wakeup.
Reported-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: fix deadlock in setting scheduler parameter to zero
sched: fix 2.6.27-rc5 couldn't boot on tulsa machine randomly
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
clockevents: make device shutdown robust
clocksource, acpi_pm.c: fix check for monotonicity
clockevents: remove WARN_ON which was used to gather information
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>
After the patch:
commit 0b2f630a28
Author: Miao Xie <miaox@cn.fujitsu.com>
Date: Fri Jul 25 01:47:21 2008 -0700
cpusets: restructure the function update_cpumask() and update_nodemask()
It might happen that 'echo 0 > /cpuset/sub/cpus' returned failure but 'cpus'
has been changed, because cpus was changed before calling heap_init() which
may return -ENOMEM.
This patch restores the orginal behavior.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On my tulsa x86-64 machine, kernel 2.6.25-rc5 couldn't boot randomly.
Basically, function __enable_runtime forgets to reset rt_rq->rt_throttled
to 0. When every cpu is up, per-cpu migration_thread is created and it runs
very fast, sometimes to mark the corresponding rt_rq->rt_throttled to 1 very
quickly. After all cpus are up, with below calling chain:
sched_init_smp => arch_init_sched_domains => build_sched_domains => ...
=> cpu_attach_domain => rq_attach_root => set_rq_online => ...
=> _enable_runtime
_enable_runtime is called against every rt_rq again, so rt_rq->rt_time is
reset to 0, but rt_rq->rt_throttled might be still 1. Later on function
do_sched_rt_period_timer couldn't reset it, and all RT tasks couldn't be
scheduled to run on that cpu. here is RT task migration_thread which is
woken up when a task is migrated to another cpu.
Below patch fixes it against 2.6.27-rc5.
Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The issue of the endless reprogramming loop due to a too small
min_delta_ns was fixed with the previous updates of the clock events
code, but we had no information about the spread of this problem. I
added a WARN_ON to get automated information via kerneloops.org and to
get some direct reports, which allowed me to analyse the affected
machines.
The WARN_ON has served its purpose and would be annoying for a release
kernel. Remove it and just keep the information about the increase of
the min_delta_ns value.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: arch_reinit_sched_domains() must destroy domains to force rebuild
sched, cpuset: rework sched domains and CPU hotplug handling (v4)
What I realized recently is that calling rebuild_sched_domains() in
arch_reinit_sched_domains() by itself is not enough when cpusets are enabled.
partition_sched_domains() code is trying to avoid unnecessary domain rebuilds
and will not actually rebuild anything if new domain masks match the old ones.
What this means is that doing
echo 1 > /sys/devices/system/cpu/sched_mc_power_savings
on a system with cpusets enabled will not take affect untill something changes
in the cpuset setup (ie new sets created or deleted).
This patch fixes restore correct behaviour where domains must be rebuilt in
order to enable MC powersaving flags.
Test on quad-core Core2 box with both CONFIG_CPUSETS and !CONFIG_CPUSETS.
Also tested on dual-core Core2 laptop. Lockdep is happy and things are working
as expected.
Signed-off-by: Max Krasnyansky <maxk@qualcomm.com>
Tested-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When a cpu is taken offline, the CPU_DYING notifiers are called on the
dying cpu. According to <linux/notifiers.h>, the cpu should be "not
running any task, not handling interrupts, soon dead".
For the current implementation, this is not true:
- __cpu_disable can fail. If it fails, then the cpu will remain alive
and happy.
- At least on x86, __cpu_disable() briefly enables the local interrupts
to handle any outstanding interrupts.
What about moving CPU_DYING down a few lines, behind the __cpu_disable()
line?
There are only two CPU_DYING handlers in the kernel right now: one in
kvm, one in the scheduler. Both should work with the patch applied
[and: I'm not sure if either one handles a failing __cpu_disable()]
The patch survives simple offlining a cpu. kvm untested due to lack
of a test setup.
Signed-off-By: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The __load_balance_iterator() returns a NULL when there's only one
sched_entity which is a task. It is caused by the following code-path.
/* Skip over entities that are not tasks */
do {
se = list_entry(next, struct sched_entity, group_node);
next = next->next;
} while (next != &cfs_rq->tasks && !entity_is_task(se));
if (next == &cfs_rq->tasks)
return NULL;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This will return NULL even when se is a task.
As a side-effect, there was a regression in sched_mc behavior since 2.6.25,
since iter_move_one_task() when it calls load_balance_start_fair(),
would not get any tasks to move!
Fix this by checking if the last entity was a task or not.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We have a bug in the calculation of the next jiffie to trigger the RTC
synchronisation. The aim here is to run sync_cmos_clock() as close as
possible to the middle of a second. Which means we want this function to
be called less than or equal to half a jiffie away from when now.tv_nsec
equals 5e8 (500000000).
If this is not the case for a given call to the function, for this purpose
instead of updating the RTC we calculate the offset in nanoseconds to the
next point in time where now.tv_nsec will be equal 5e8. The calculated
offset is then converted to jiffies as these are the unit used by the
timer.
Hovewer timespec_to_jiffies() used here uses a ceil()-type rounding mode,
where the resulting value is rounded up. As a result the range of
now.tv_nsec when the timer will trigger is from 5e8 to 5e8 + TICK_NSEC
rather than the desired 5e8 - TICK_NSEC / 2 to 5e8 + TICK_NSEC / 2.
As a result if for example sync_cmos_clock() happens to be called at the
time when now.tv_nsec is between 5e8 + TICK_NSEC / 2 and 5e8 to 5e8 +
TICK_NSEC, it will simply be rescheduled HZ jiffies later, falling in the
same range of now.tv_nsec again. Similarly for cases offsetted by an
integer multiple of TICK_NSEC.
This change addresses the problem by subtracting TICK_NSEC / 2 from the
nanosecond offset to the next point in time where now.tv_nsec will be
equal 5e8, effectively shifting the following rounding in
timespec_to_jiffies() so that it produces a rounded-to-nearest result.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I found that 2.6.27-rc5-mm1 does not compile with gcc 3.4.6.
The error is:
CC kernel/sched.o
kernel/sched.c: In function `start_rt_bandwidth':
kernel/sched.c:208: sorry, unimplemented: inlining failed in call to 'rt_bandwidth_enabled': function body not available
kernel/sched.c:214: sorry, unimplemented: called from here
make[1]: *** [kernel/sched.o] Error 1
make: *** [kernel] Error 2
It seems that the gcc 3.4.6 requires full inline definition before first usage.
The patch below fixes the compilation problem.
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> (if needed>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Until the C1E patches arrived there where no users of periodic broadcast
before switching to oneshot mode. Now we need to trigger a possible
waiter for a periodic broadcast when switching to oneshot mode.
Otherwise we can starve them for ever.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Spencer reported a problem where utime and stime were going negative despite
the fixes in commit b27f03d4bd. The suspected
reason for the problem is that signal_struct maintains it's own utime and
stime (of exited tasks), these are not updated using the new task_utime()
routine, hence sig->utime can go backwards and cause the same problem
to occur (sig->utime, adds tsk->utime and not task_utime()). This patch
fixes the problem
TODO: using max(task->prev_utime, derived utime) works for now, but a more
generic solution is to implement cputime_max() and use the cputime_gt()
function for comparison.
Reported-by: spencer@bluehost.com
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If HLT stops the TSC, we'll fail to account idle time, thereby inflating the
actual process times. Fix this by re-calibrating the clock against GTOD when
leaving nohz mode.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The C1E/HPET bug reports on AMDX2/RS690 systems where tracked down to a
too small value of the HPET minumum delta for programming an event.
The clockevents code needs to enforce an interrupt event on the clock event
device in some cases. The enforcement code was stupid and naive, as it just
added the minimum delta to the current time and tried to reprogram the device.
When the minimum delta is too small, then this loops forever.
Add a sanity check. Allow reprogramming to fail 3 times, then print a warning
and double the minimum delta value to make sure, that this does not happen again.
Use the same function for both tick-oneshot and tick-broadcast code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
While chasing the C1E/HPET bugreports I went through the clock events
code inch by inch and found that the broadcast device can be initialized
and shutdown multiple times. Multiple shutdowns are not critical, but
useless waste of time. Multiple initializations are simply broken. Another
CPU might have the device in use already after the first initialization and
the second init could just render it unusable again.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In tick_oneshot_setup we program the device to the given next_event,
but we do not check the return value. We need to make sure that the
device is programmed enforced so the interrupt handler engine starts
working. Split out the reprogramming function from tick_program_event()
and call it with the device, which was handed in to tick_setup_oneshot().
Set the force argument, so the devices is firing an interrupt.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The reprogramming of the periodic broadcast handler was broken,
when the first programming returned -ETIME. The clockevents code
stores the new expiry value in the clock events device next_event field
only when the programming time has not been elapsed yet. The loop in
question calculates the new expiry value from the next_event value
and therefor never increases.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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>
We should've set refcount on the root sysctl table; otherwise we'll blow
up the first time we get down to zero dynamically registered sysctl
tables.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make PM_QOS and CPU_IDLE play nicer when run with the RT-Preempt kernel.
The purpose of the patch is to remove the spin_lock around the read in the
function pm_qos_requirement - since spinlocks can sleep in -rt and this
function is called from idle.
CPU_IDLE polls the target_value's of some of the pm_qos parameters from
the idle loop causing sleeping locking warnings. Changing the
target_value to an atomic avoids this issue.
Remove the spinlock in pm_qos_requirement by making target_value an atomic
type.
Signed-off-by: mark gross <mgross@linux.intel.com>
Signed-off-by: John Kacur <jkacur@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We don't change pid_ns->child_reaper when the main thread of the
subnamespace init exits. As Robert Rex <robert.rex@exasol.com> pointed
out this is wrong.
Yes, the re-parenting itself works correctly, but if the reparented task
exits it needs ->parent->nsproxy->pid_ns in do_notify_parent(), and if the
main thread is zombie its ->nsproxy was already cleared by
exit_task_namespaces().
Introduce the new function, find_new_reaper(), which finds the new
->parent for the re-parenting and changes ->child_reaper if needed. Kill
the now unneeded exit_child_reaper().
Also move the changing of ->child_reaper from zap_pid_ns_processes() to
find_new_reaper(), this consolidates the games with ->child_reaper and
makes it stable under tasklist_lock.
Addresses http://bugzilla.kernel.org/show_bug.cgi?id=11391
Reported-by: Robert Rex <robert.rex@exasol.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zap_pid_ns_processes() sets pid_ns->child_reaper = NULL, this is wrong.
Yes, we have already killed all tasks in this namespace, and sys_wait4()
doesn't see any child. But this doesn't mean ->children list is empty, we
may have EXIT_DEAD tasks which are not visible to do_wait(). In that case
the subsequent forget_original_parent() will crash the kernel because it
will try to re-parent these tasks to the NULL reaper.
Even if there are no childs, it is not good that forget_original_parent()
uses reaper == NULL.
Change the code to set ->child_reaper = init_pid_ns.child_reaper instead.
We could use pid_ns->parent->child_reaper as well, I think this does not
really matter. These EXIT_DEAD tasks are not visible to the new ->parent
after re-parenting, they will silently do release_task() eventually.
Note that we must change ->child_reaper, otherwise
forget_original_parent() will use reaper == father, and in that case we
will hit the (correct) BUG_ON(!list_empty(&father->children)).
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The recent commit 16d9679f33caf7e683471647d1472bfe133d858 changed
check_hung_task() to filter out the TASK_KILLABLE tasks. We can
move this check to the caller which has to test t->state anyway.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix kernel-doc warning for new function:
Warning(linux-2.6.27-rc5-git2//kernel/resource.c:448): No description found for parameter 'root'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
got rid of compilation warning:
ISO C90 forbids mixed declarations and code
Signed-off-by: Cordelia Sam <cordesam@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Not used anywhere yet, but this complements the existing plain
'insert_resource()' functionality with a version that can expand the
resource we are adding in order to fix up any conflicts it has with
existing resources.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pulling the ethernet cable on a 2.6.27-rc system with NFS mounts
currently leads to an ongoing flood of soft lockup detector backtraces
for all tasks blocked on the NFS mounts when the hickup takes
longer than 120s.
I don't think NFS problems should be all that noisy.
Luckily there's a reasonably easy way to distingush this case.
Don't report task softlockup warnings for tasks in TASK_KILLABLE
state, which is used by the network file systems.
I believe this patch is a 2.6.27 candidate.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In accordance with commit f42ac38c59
("ftrace: disable tracing for suspend to ram"), disable tracing
around the suspend code in hibernation code paths.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It fixes an accounting bug where we would continue accumulating runtime
even though the bandwidth control is disabled. This would lead to very long
throttle periods once bandwidth control gets turned on again.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
