It appears I inadvertly introduced rq->lock recursion to the
hrtimer_start() path when I delegated running already expired
timers to softirq context.
This patch fixes it by introducing a __hrtimer_start_range_ns()
method that will not use raise_softirq_irqoff() but
__raise_softirq_irqoff() which avoids the wakeup.
It then also changes schedule() to check for pending softirqs and
do the wakeup then, I'm not quite sure I like this last bit, nor
am I convinced its really needed.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus@samba.org
LKML-Reference: <20090313112301.096138802@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix lazy context switch API
Pass the previous and next tasks into the context switch start
end calls, so that the called functions can properly access the
task state (esp in end_context_switch, in which the next task
is not yet completely current).
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Impact: simplification, prepare for later changes
Make lazy cpu mode more specific to context switching, so that
it makes sense to do more context-switch specific things in
the callbacks.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Fix kernel-doc errors in sched.c: the structs don't have
kernel-doc notation and the short function description needs to
be one line only.
Error(kernel/sched.c:3197): cannot understand prototype: 'struct sd_lb_stats '
Error(kernel/sched.c:3228): cannot understand prototype: 'struct sg_lb_stats '
Error(kernel/sched.c:3375): duplicate section name 'Description'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Impact: cleanup, new schedstat ABI
Since they are used on in statistics and are always set to zero, the
following fields from struct rq have been removed: yld_exp_empty,
yld_act_empty and yld_both_empty.
Both Sched Debug and SCHEDSTAT_VERSION versions has also been
incremented since ABIs have been changed.
The schedtop tool has been updated to properly handle new version of
schedstat:
http://rt.wiki.kernel.org/index.php/Schedtop_utility
Signed-off-by: Luis Henriques <henrix@sapo.pt>
Acked-by: Gregory Haskins <ghaskins@novell.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20090324221002.GA10061@hades.domain.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix circular locking
Steven reports a circular locking from alloc_cpumask_var doing
a wakeup. We get rid of this using the tried-and-true technique
of using a per-cpu cpumask_var_t rather than doing an alloc
every time.
Simpler and more robust than a rare, implicit allocation within
an atomic codepath.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <alpine.DEB.2.00.0903181729360.31583@gandalf.stny.rr.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There were 3 invocations of task_hot() in can_migrate_task().
Replace these 3 invocations by only one invocation, cached in
a local variable.
Signed-off-by: Luis Henriques <henrix@sapo.pt>
LKML-Reference: <20090316195902.GA6197@hades.domain.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
This is presumably what those definitions are for, and while all archs
define cpu_core_map/cpu_sibling map, that's changing (eg. x86 wants to
change it to a pointer).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Impact: more precise avg_overlap metric - better load-balancing
avg_overlap is used to measure the runtime overlap of the waker and
wakee.
However, when a process changes behaviour, eg a pipe becomes
un-congested and we don't need to go to sleep after a wakeup
for a while, the avg_overlap value grows stale.
When running we use the avg runtime between preemption as a
measure for avg_overlap since the amount of runtime can be
correlated to cache footprint.
The longer we run, the less likely we'll be wanting to be
migrated to another CPU.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1236709131.25234.576.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: micro-optimization
We can avoid the sched domain walk on try_to_wake_up() when we know
there are no groups.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1236603381.8389.455.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix function graph trace hang / drop pointless softirq on UP
While debugging a function graph trace hang on an old PII, I saw
that it consumed most of its time on the timer interrupt. And
the domain rebalancing softirq was the most concerned.
The timer interrupt calls trigger_load_balance() which will
decide if it is worth to schedule a rebalancing softirq.
In case of builtin UP kernel, no problem arises because there is
no domain question.
In case of builtin SMP kernel running on an SMP box, still no
problem, the softirq will be raised each time we reach the
next_balance time.
In case of builtin SMP kernel running on a UP box (most distros
provide default SMP kernels, whatever the box you have), then
the CPU is attached to the NULL sched domain. So a kind of
unexpected behaviour happen:
trigger_load_balance() -> raises the rebalancing softirq later
on softirq: run_rebalance_domains() -> rebalance_domains() where
the for_each_domain(cpu, sd) is not taken because of the NULL
domain we are attached at. Which means rq->next_balance is never
updated. So on the next timer tick, we will enter
trigger_load_balance() which will always reschedule() the
rebalacing softirq:
if (time_after_eq(jiffies, rq->next_balance))
raise_softirq(SCHED_SOFTIRQ);
So for each tick, we process this pointless softirq.
This patch fixes it by checking if we are attached to the null
domain before raising the softirq, another possible fix would be
to set the maximal possible JIFFIES value to rq->next_balance if
we are attached to the NULL domain.
v2: build fix on UP
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <49af242d.1c07d00a.32d5.ffffc019@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: micro-optimization
Parameter "prev" is not used really.
Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix hung task with certain (non-default) rt-limit settings
Corey Hickey reported that on using setuid to change the uid of a
rt process, the process would be unkillable and not be running.
This is because there was no rt runtime for that user group. Add
in a check to see if a user can attach an rt task to its task group.
On failure, return EINVAL, which is also returned in
CONFIG_CGROUP_SCHED.
Reported-by: Corey Hickey <bugfood-ml@fatooh.org>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix incorrect condition check
No need to start rt bandwidth timer when rt bandwidth is disabled.
If this timer starts, it may stop at sched_rt_period_timer() on the first time.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
There are two allocated per-cpu accessor macros with almost identical
spelling. The original and far more popular is per_cpu_ptr (44
files), so change over the other 4 files.
tj: kill percpu_ptr() and update UP too
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: mingo@redhat.com
Cc: lenb@kernel.org
Cc: cpufreq@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
#define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
So it's better to use TASK_NICE here.
Signed-off-by: WANG Cong <wangcong@zeuux.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: struct rq size optimization
The idle_at_tick in struct rq is only used in SMP settings
and it does not make sense to have this in the rq in an UP setup.
Signed-off-by: Henrik Austad <henrik@austad.us>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
