The implementation is utterly broken, resulting in all processes being
allows to move tasks between sets (as long as they have access to the
"tasks" attribute), and upstream is heading towards checking only
capability anyway, so let's get rid of this code.
BUG=b:31790445,chromium:647994
TEST=Boot android container, examine logcat
Change-Id: I2f780a5992c34e52a8f2d0b3557fc9d490da2779
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/394967
Reviewed-by: Ricky Zhou <rickyz@chromium.org>
Reviewed-by: John Stultz <john.stultz@linaro.org>
commit 135e8c9250dd5c8c9aae5984fde6f230d0cbfeaf upstream.
The origin of the issue I've seen is related to
a missing memory barrier between check for task->state and
the check for task->on_rq.
The task being woken up is already awake from a schedule()
and is doing the following:
do {
schedule()
set_current_state(TASK_(UN)INTERRUPTIBLE);
} while (!cond);
The waker, actually gets stuck doing the following in
try_to_wake_up():
while (p->on_cpu)
cpu_relax();
Analysis:
The instance I've seen involves the following race:
CPU1 CPU2
while () {
if (cond)
break;
do {
schedule();
set_current_state(TASK_UN..)
} while (!cond);
wakeup_routine()
spin_lock_irqsave(wait_lock)
raw_spin_lock_irqsave(wait_lock) wake_up_process()
} try_to_wake_up()
set_current_state(TASK_RUNNING); ..
list_del(&waiter.list);
CPU2 wakes up CPU1, but before it can get the wait_lock and set
current state to TASK_RUNNING the following occurs:
CPU3
wakeup_routine()
raw_spin_lock_irqsave(wait_lock)
if (!list_empty)
wake_up_process()
try_to_wake_up()
raw_spin_lock_irqsave(p->pi_lock)
..
if (p->on_rq && ttwu_wakeup())
..
while (p->on_cpu)
cpu_relax()
..
CPU3 tries to wake up the task on CPU1 again since it finds
it on the wait_queue, CPU1 is spinning on wait_lock, but immediately
after CPU2, CPU3 got it.
CPU3 checks the state of p on CPU1, it is TASK_UNINTERRUPTIBLE and
the task is spinning on the wait_lock. Interestingly since p->on_rq
is checked under pi_lock, I've noticed that try_to_wake_up() finds
p->on_rq to be 0. This was the most confusing bit of the analysis,
but p->on_rq is changed under runqueue lock, rq_lock, the p->on_rq
check is not reliable without this fix IMHO. The race is visible
(based on the analysis) only when ttwu_queue() does a remote wakeup
via ttwu_queue_remote. In which case the p->on_rq change is not
done uder the pi_lock.
The result is that after a while the entire system locks up on
the raw_spin_irqlock_save(wait_lock) and the holder spins infintely
Reproduction of the issue:
The issue can be reproduced after a long run on my system with 80
threads and having to tweak available memory to very low and running
memory stress-ng mmapfork test. It usually takes a long time to
reproduce. I am trying to work on a test case that can reproduce
the issue faster, but thats work in progress. I am still testing the
changes on my still in a loop and the tests seem OK thus far.
Big thanks to Benjamin and Nick for helping debug this as well.
Ben helped catch the missing barrier, Nick caught every missing
bit in my theory.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[ Updated comment to clarify matching barriers. Many
architectures do not have a full barrier in switch_to()
so that cannot be relied upon. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <nicholas.piggin@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e02cce7b-d9ca-1ad0-7a61-ea97c7582b37@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Conflicts:
in fs/proc/task_mmu.c:
looks like vma_get_anon_name() want have a name for anonymous
vma when there is no name used in vma. commit: 586278d78b
The name show is after any other names, so it maybe covered.
but anyway, it just a show here.
Because sched_setscheduler() checks p->flags & PF_NO_SETAFFINITY
without locks, a caller might observe an old value and race with the
set_cpus_allowed_ptr() call from __kthread_bind() and effectively undo
it:
__kthread_bind()
do_set_cpus_allowed()
<SYSCALL>
sched_setaffinity()
if (p->flags & PF_NO_SETAFFINITIY)
set_cpus_allowed_ptr()
p->flags |= PF_NO_SETAFFINITY
Fix the bug by putting everything under the regular scheduler locks.
This also closes a hole in the serialization of task_struct::{nr_,}cpus_allowed.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dedekind1@gmail.com
Cc: juri.lelli@arm.com
Cc: mgorman@suse.de
Cc: riel@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20150515154833.545640346@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 25834c73f9)
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
BUG=chrome-os-partner:44828
TEST=Boot kernel on Oak.
TEST=smaug-release and strago-release trybots.
Change-Id: Id3c898c5ee1a22ed704e83f2ecf5f78199280d38
Reviewed-on: https://chromium-review.googlesource.com/321264
Commit-Ready: Ricky Liang <jcliang@chromium.org>
Tested-by: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Ricky Liang <jcliang@chromium.org>
Conflicts:
kernel/sched/core.c
The current kernel allows to use either PELT or WALT to track CPUs utilizations.
One of the main differences between the two approaches is that PELT
tracks only utilization of SCHED_OTHER classes while WALT tracks all tasks
with a single signal.
The current sched_freq_tick does not make this distinction and, when WALT
is in use, we end up adding multiple time the contribution related to
the RT and DL classes. This patch fixes this issue by:
1. providing two different code paths for PELT and WALT, thus granting that
when we switch to PELT we get the original behaviour based on the assumption
that class aggregations is done underneath by SchedFreq.
2. avoiding the double accounting of DL and RT workloads, when WALT is in use,
by just adding a margin to the original WALT signal when we need to check
if the CFS capacity has to be increased.
Change-Id: I7326fd50e868e97fb5e12351917e9d2969bfdae7
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
During scheduler tick handling, the frequency was being set to
max-freq if the current frequency is less than the current
utilization. Change to just request "right" frequency instead
of max.
BUG: 29871410
Change-Id: I6fe65b14413da44b1520ba116f72320083eb92f8
use a window based view of time in order to track task
demand and CPU utilization in the scheduler.
Window Assisted Load Tracking (WALT) implementation credits:
Srivatsa Vaddagiri, Steve Muckle, Syed Rameez Mustafa, Joonwoo Park,
Pavan Kumar Kondeti, Olav Haugan
2016-03-06: Integration with EAS/refactoring by Vikram Mulukutla
and Todd Kjos
Change-Id: I21408236836625d4e7d7de1843d20ed5ff36c708
Includes fixes for issues:
eas/walt: Use walt_ktime_clock() instead of ktime_get_ns() to avoid a
race resulting in watchdog resets
BUG: 29353986
Change-Id: Ic1820e22a136f7c7ebd6f42e15f14d470f6bbbdb
Handle walt accounting anomoly during resume
During resume, there is a corner case where on wakeup, a task's
prev_runnable_sum can go negative. This is a workaround that
fixes the condition and warns (instead of crashing).
BUG: 29464099
Change-Id: I173e7874324b31a3584435530281708145773508
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Srinath Sridharan <srinathsr@google.com>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
[jstultz: fwdported to 4.4]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Contains:
sched/tune: fix accounting for runnable tasks (1/5)
The accounting for tasks into boost groups of different CPUs is currently
broken mainly because:
a) we do not properly track the change of boost group of a RUNNABLE task
b) there are race conditions between migration code and accounting code
This patch provides a fixes to ensure enqueue/dequeue
accounting also for throttled tasks.
Without this patch is can happen that a task is enqueued into a throttled
RQ thus not being accounted for the boosting of the corresponding RQ.
We could argue that a throttled task should not boost a CPU, however:
a) properly implementing CPU boosting considering throttled tasks will
increase a lot the complexity of the solution
b) it's not easy to quantify the benefits introduced by such a more
complex solution
Since task throttling requires the usage of the CFS bandwidth controller,
which is not widely used on mobile systems (at least not by Android kernels
so far), for the time being we go for the simple solution and boost also
for throttled RQs.
sched/tune: fix accounting for runnable tasks (2/5)
This patch provides the code required to enforce proper locking.
A per boost group spinlock has been added to grant atomic
accounting of tasks as well as to serialise enqueue/dequeue operations,
triggered by tasks migrations, with cgroups's attach/detach operations.
sched/tune: fix accounting for runnable tasks (3/5)
This patch adds cgroups {allow,can,cancel}_attach callbacks.
Since a task can be migrated between boost groups while it's running,
the CGroups's attach callbacks have been added to properly migrate
boost contributions of RUNNABLE tasks.
The RQ's lock is used to serialise enqueue/dequeue operations, triggered
by tasks migrations, with cgroups's attach/detach operations. While the
SchedTune's CPU lock is used to grant atrocity of the accounting within
the CPU.
NOTE: the current implementation does not allows a concurrent CPU migration
and CGroups change.
sched/tune: fix accounting for runnable tasks (4/5)
This fixes accounting for exiting tasks by adding a dedicated call early
in the do_exit() syscall, which disables SchedTune accounting as soon as a
task is flagged PF_EXITING.
This flag is set before the multiple dequeue/enqueue dance triggered
by cgroup_exit() which is useful only to inject useless tasks movements
thus increasing possibilities for race conditions with the migration code.
The schedtune_exit_task() call does the last dequeue of a task from its
current boost group. This is a solution more aligned with what happens in
mainline kernels (>v4.4) where the exit_cgroup does not move anymore a dying
task to the root control group.
sched/tune: fix accounting for runnable tasks (5/5)
To avoid accounting issues at startup, this patch disable the SchedTune
accounting until the required data structures have been properly
initialized.
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
[jstultz: fwdported to 4.4]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Doing a Exponential moving average per nr_running++/-- does not
guarantee a fixed sample rate which induces errors if there are lots of
threads being enqueued/dequeued from the rq (Linpack mt). Instead of
keeping track of the avg, the scheduler now keeps track of the integral
of nr_running and allows the readers to perform filtering on top.
Original-author: Sai Charan Gurrappadi <sgurrappadi@nvidia.com>
Change-Id: Id946654f32fa8be0eaf9d8fa7c9a8039b5ef9fab
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/174694
Reviewed-on: https://chromium-review.googlesource.com/272853
[jstultz: fwdported to 4.4]
Signed-off-by: John Stultz <john.stultz@linaro.org>
This patch makes the energy data available via procfs. The related files
are placed as sub-directory named 'energy' inside the
/proc/sys/kernel/sched_domain/cpuX/domainY/groupZ directory for those
cpu/domain/group tuples which have energy information.
The following example depicts the contents of
/proc/sys/kernel/sched_domain/cpu0/domain0/group[01] for a system which
has energy information attached to domain level 0.
├── cpu0
│ ├── domain0
│ │ ├── busy_factor
│ │ ├── busy_idx
│ │ ├── cache_nice_tries
│ │ ├── flags
│ │ ├── forkexec_idx
│ │ ├── group0
│ │ │ └── energy
│ │ │ ├── cap_states
│ │ │ ├── idle_states
│ │ │ ├── nr_cap_states
│ │ │ └── nr_idle_states
│ │ ├── group1
│ │ │ └── energy
│ │ │ ├── cap_states
│ │ │ ├── idle_states
│ │ │ ├── nr_cap_states
│ │ │ └── nr_idle_states
│ │ ├── idle_idx
│ │ ├── imbalance_pct
│ │ ├── max_interval
│ │ ├── max_newidle_lb_cost
│ │ ├── min_interval
│ │ ├── name
│ │ ├── newidle_idx
│ │ └── wake_idx
│ └── domain1
│ ├── busy_factor
│ ├── busy_idx
│ ├── cache_nice_tries
│ ├── flags
│ ├── forkexec_idx
│ ├── idle_idx
│ ├── imbalance_pct
│ ├── max_interval
│ ├── max_newidle_lb_cost
│ ├── min_interval
│ ├── name
│ ├── newidle_idx
│ └── wake_idx
The files 'nr_idle_states' and 'nr_cap_states' contain a scalar value
whereas 'idle_states' and 'cap_states' contain a vector of power
consumption at this idle state respectively (compute capacity, power
consumption) at this capacity state.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Since the true utilization of a long running task is not detectable
while it is running and might be bigger than the current cpu capacity,
create the maximum cpu capacity head room by requesting the maximum
cpu capacity once the cpu usage plus the capacity margin exceeds the
current capacity. This is also done to try to harm the performance of
a task the least.
Original fair-class only version authored by Juri Lelli
<juri.lelli@arm.com>.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Steve Muckle <smuckle@linaro.org>
Patch "sched/fair: add triggers for OPP change requests" introduced OPP
change triggers for enqueue_task_fair(), but the trigger was operating only
for wakeups. Fact is that it makes sense to consider wakeup_new also (i.e.,
fork()), as we don't know anything about a newly created task and thus we
most certainly want to jump to max OPP to not harm performance too much.
However, it is not currently possible (or at least it wasn't evident to me
how to do so :/) to tell new wakeups from other (non wakeup) operations.
This patch introduces an additional flag in sched.h that is only set at
fork() time and it is then consumed in enqueue_task_fair() for our purpose.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Steve Muckle <smuckle@linaro.org>
struct sched_group_capacity currently represents the compute capacity
sum of all cpus in the sched_group. Unless it is divided by the
group_weight to get the average capacity per cpu it hides differences in
cpu capacity for mixed capacity systems (e.g. high RT/IRQ utilization or
ARM big.LITTLE). But even the average may not be sufficient if the group
covers cpus of different capacities. Instead, by extending struct
sched_group_capacity to indicate max per-cpu capacity in the group a
suitable group for a given task utilization can easily be found such
that cpus with reduced capacity can be avoided for tasks with high
utilization (not implemented by this patch).
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Wakeup balancing uses cpu capacity awareness and needs to know the
system-wide maximum cpu capacity.
Patch "sched: Store system-wide maximum cpu capacity in root domain"
finds the system-wide maximum cpu capacity during scheduler domain
hierarchy setup. This is sufficient as long as maximum frequency
invariance is not enabled.
If it is enabled, the system-wide maximum cpu capacity can change
between scheduler domain hierarchy setups due to frequency capping.
The cpu capacity is changed in update_cpu_capacity() which is called in
load balance on the lowest scheduler domain hierarchy level. To be able
to know if a change in cpu capacity for a certain cpu also has an effect
on the system-wide maximum cpu capacity it is normally necessary to
iterate over all cpus. This would be way too costly. That's why this
patch follows a different approach.
The unsigned long max_cpu_capacity value in struct root_domain is
replaced with a struct max_cpu_capacity, containing value (the
max_cpu_capacity) and cpu (the cpu index of the cpu providing the
maximum cpu_capacity).
Changes to the system-wide maximum cpu capacity and the cpu index are
made if:
1 System-wide maximum cpu capacity < cpu capacity
2 System-wide maximum cpu capacity > cpu capacity and cpu index == cpu
There are no changes to the system-wide maximum cpu capacity in all
other cases.
Atomic read and write access to the pair (max_cpu_capacity.val,
max_cpu_capacity.cpu) is enforced by max_cpu_capacity.lock.
The access to max_cpu_capacity.val in task_fits_max() is still performed
without taking the max_cpu_capacity.lock.
The code to set max cpu capacity in build_sched_domains() has been
removed because the whole functionality is now provided by
update_cpu_capacity() instead.
This approach can introduce errors temporarily, e.g. in case the cpu
currently providing the max cpu capacity has its cpu capacity lowered
due to frequency capping and calls update_cpu_capacity() before any cpu
which might provide the max cpu now.
There is also an outstanding question:
Should the cpu capacity of a cpu going idle be set to a very small
value?
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
For energy-aware load-balancing decisions it is necessary to know the
energy consumption estimates of groups of cpus. This patch introduces a
basic function, sched_group_energy(), which estimates the energy
consumption of the cpus in the group and any resources shared by the
members of the group.
NOTE: The function has five levels of identation and breaks the 80
character limit. Refactoring is necessary.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Add another member to the family of per-cpu sched_domain shortcut
pointers. This one, sd_ea, points to the highest level at which energy
model is provided. At this level and all levels below all sched_groups
have energy model data attached.
Partial energy model information is possible but restricted to providing
energy model data for lower level sched_domains (sd_ea and below) and
leaving load-balancing on levels above to non-energy-aware
load-balancing. For example, it is possible to apply energy-aware
scheduling within each socket on a multi-socket system and let normal
scheduling handle load-balancing between sockets.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
cpufreq is currently keeping it a secret which cpus are sharing
clock source. The scheduler needs to know about clock domains as well
to become more energy aware. The SD_SHARE_CAP_STATES domain flag
indicates whether cpus belonging to the sched_domain share capacity
states (P-states).
There is no connection with cpufreq (yet). The flag must be set by
the arch specific topology code.
cc: Russell King <linux@arm.linux.org.uk>
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
The sched_group_energy (sge) pointer of the first sched_group (sg) in
the sched_domain (sd) is initialized to point to the appropriate (in
terms of sd level and cpu) sge data defined in the arch and so to the
correct part of the Energy Model (EM).
Energy-aware scheduling allows that a system has only EM data up to a
certain sd level (so called highest energy aware balancing sd level).
A check in init_sched_energy() enforces that all sd's below this sd
level contain EM data.
The 'int cpu' parameter of sched_domain_energy_f requires that
check_sched_energy_data() makes sure that all cpus spanned by a sg
are provisioned with the same EM data.
This patch has also been tested with feature FORCE_SD_OVERLAP enabled.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
To be able to compare the capacity of the target cpu with the highest
cpu capacity of the system in the wakeup path, store the system-wide
maximum cpu capacity in the root domain.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
commit 444969223c81c7d0a95136b7b4cfdcfbc96ac5bd upstream.
The following commit:
9642d18eee ("nohz: Affine unpinned timers to housekeepers")'
intended to affine unpinned timers to housekeepers:
unpinned timers(full dynaticks, idle) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(full dynaticks, busy) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(houserkeepers, idle) => nearest busy housekeepers(otherwise, fallback to itself)
However, the !idle_cpu(i) && is_housekeeping_cpu(cpu) check modified the
intention to:
unpinned timers(full dynaticks, idle) => any housekeepers(no mattter cpu topology)
unpinned timers(full dynaticks, busy) => any housekeepers(no mattter cpu topology)
unpinned timers(housekeepers, idle) => any busy cpus(otherwise, fallback to any housekeepers)
This patch fixes it by checking if there are busy housekeepers nearby,
otherwise falls to any housekeepers/itself. After the patch:
unpinned timers(full dynaticks, idle) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(full dynaticks, busy) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(housekeepers, idle) => nearest busy housekeepers(otherwise, fallback to itself)
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Fixed the changelog. ]
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: 'commit 9642d18eee ("nohz: Affine unpinned timers to housekeepers")'
Link: http://lkml.kernel.org/r/1462344334-8303-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 57675cb976eff977aefb428e68e4e0236d48a9ff upstream.
Lengthy output of sysrq-w may take a lot of time on slow serial console.
Currently we reset NMI-watchdog on the current CPU to avoid spurious
lockup messages. Sometimes this doesn't work since softlockup watchdog
might trigger on another CPU which is waiting for an IPI to proceed.
We reset softlockup watchdogs on all CPUs, but we do this only after
listing all tasks, and this may be too late on a busy system.
So, reset watchdogs CPUs earlier, in for_each_process_thread() loop.
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1465474805-14641-1-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 29d6455178a09e1dc340380c582b13356227e8df upstream.
Until now, hitting this BUG_ON caused a recursive oops (because oops
handling involves do_exit(), which calls into the scheduler, which in
turn raises an oops), which caused stuff below the stack to be
overwritten until a panic happened (e.g. via an oops in interrupt
context, caused by the overwritten CPU index in the thread_info).
Just panic directly.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 2f5177f0fd7e531b26d54633be62d1d4cb94621c upstream.
The CPU controller hasn't kept up with the various changes in the whole
cgroup initialization / destruction sequence, and commit:
2e91fa7f6d ("cgroup: keep zombies associated with their original cgroups")
caused it to explode.
The reason for this is that zombies do not inhibit css_offline() from
being called, but do stall css_released(). Now we tear down the cfs_rq
structures on css_offline() but zombies can run after that, leading to
use-after-free issues.
The solution is to move the tear-down to css_released(), which
guarantees nobody (including no zombies) is still using our cgroup.
Furthermore, a few simple cleanups are possible too. There doesn't
appear to be any point to us using css_online() (anymore?) so fold that
in css_alloc().
And since cgroup code guarantees an RCU grace period between
css_released() and css_free() we can forgo using call_rcu() and free the
stuff immediately.
Suggested-by: Tejun Heo <tj@kernel.org>
Reported-by: Kazuki Yamaguchi <k@rhe.jp>
Reported-by: Niklas Cassel <niklas.cassel@axis.com>
Tested-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2e91fa7f6d ("cgroup: keep zombies associated with their original cgroups")
Link: http://lkml.kernel.org/r/20160316152245.GY6344@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit e9532e69b8d1d1284e8ecf8d2586de34aec61244 upstream.
On CPU hotplug the steal time accounting can keep a stale rq->prev_steal_time
value over CPU down and up. So after the CPU comes up again the delta
calculation in steal_account_process_tick() wreckages itself due to the
unsigned math:
u64 steal = paravirt_steal_clock(smp_processor_id());
steal -= this_rq()->prev_steal_time;
So if steal is smaller than rq->prev_steal_time we end up with an insane large
value which then gets added to rq->prev_steal_time, resulting in a permanent
wreckage of the accounting. As a consequence the per CPU stats in /proc/stat
become stale.
Nice trick to tell the world how idle the system is (100%) while the CPU is
100% busy running tasks. Though we prefer realistic numbers.
None of the accounting values which use a previous value to account for
fractions is reset at CPU hotplug time. update_rq_clock_task() has a sanity
check for prev_irq_time and prev_steal_time_rq, but that sanity check solely
deals with clock warps and limits the /proc/stat visible wreckage. The
prev_time values are still wrong.
Solution is simple: Reset rq->prev_*_time when the CPU is plugged in again.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: commit 095c0aa83e "sched: adjust scheduler cpu power for stolen time"
Fixes: commit aa48380851 "sched: Remove irq time from available CPU power"
Fixes: commit e6e6685acc "KVM guest: Steal time accounting"
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603041539490.3686@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 9c03ee147193645be4c186d3688232fa438c57c7 upstream.
The following PowerPC commit:
c118baf802 ("arch/powerpc/mm/numa.c: do not allocate bootmem memory for non existing nodes")
avoids allocating bootmem memory for non existent nodes.
But when DEBUG_PER_CPU_MAPS=y is enabled, my powerNV system failed to boot
because in sched_init_numa(), cpumask_or() operation was done on
unallocated nodes.
Fix that by making cpumask_or() operation only on existing nodes.
[ Tested with and w/o DEBUG_PER_CPU_MAPS=y on x86 and PowerPC. ]
Reported-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: <gkurz@linux.vnet.ibm.com>
Cc: <grant.likely@linaro.org>
Cc: <nikunj@linux.vnet.ibm.com>
Cc: <vdavydov@parallels.com>
Cc: <linuxppc-dev@lists.ozlabs.org>
Cc: <linux-mm@kvack.org>
Cc: <peterz@infradead.org>
Cc: <benh@kernel.crashing.org>
Cc: <paulus@samba.org>
Cc: <mpe@ellerman.id.au>
Cc: <anton@samba.org>
Link: http://lkml.kernel.org/r/1452884483-11676-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
- Return -EINVAL when cgroups support isn't enabled
- Add allow_attach callback in CPU cgroups
Change-Id: Id3360b4a39919524fc4b6fcbd44fa2050009f000
Signed-off-by: Rom Lemarchand <romlem@android.com>
The following commit which went into mainline through networking tree
3b13758f51 ("cgroups: Allow dynamically changing net_classid")
conflicts in net/core/netclassid_cgroup.c with the following pending
fix in cgroup/for-4.4-fixes.
1f7dd3e5a6 ("cgroup: fix handling of multi-destination migration from subtree_control enabling")
The former separates out update_classid() from cgrp_attach() and
updates it to walk all fds of all tasks in the target css so that it
can be used from both migration and config change paths. The latter
drops @css from cgrp_attach().
Resolve the conflict by making cgrp_attach() call update_classid()
with the css from the first task. We can revive @tset walking in
cgrp_attach() but given that net_cls is v1 only where there always is
only one target css during migration, this is fine.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Nina Schiff <ninasc@fb.com>
Oleg noticed that its possible to falsely observe p->on_cpu == 0 such
that we'll prematurely continue with the wakeup and effectively run p on
two CPUs at the same time.
Even though the overlap is very limited; the task is in the middle of
being scheduled out; it could still result in corruption of the
scheduler data structures.
CPU0 CPU1
set_current_state(...)
<preempt_schedule>
context_switch(X, Y)
prepare_lock_switch(Y)
Y->on_cpu = 1;
finish_lock_switch(X)
store_release(X->on_cpu, 0);
try_to_wake_up(X)
LOCK(p->pi_lock);
t = X->on_cpu; // 0
context_switch(Y, X)
prepare_lock_switch(X)
X->on_cpu = 1;
finish_lock_switch(Y)
store_release(Y->on_cpu, 0);
</preempt_schedule>
schedule();
deactivate_task(X);
X->on_rq = 0;
if (X->on_rq) // false
if (t) while (X->on_cpu)
cpu_relax();
context_switch(X, ..)
finish_lock_switch(X)
store_release(X->on_cpu, 0);
Avoid the load of X->on_cpu being hoisted over the X->on_rq load.
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Explain how the control dependency and smp_rmb() end up providing
ACQUIRE semantics and pair with smp_store_release() in
finish_lock_switch().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
root_domain::rto_mask allocated through alloc_cpumask_var()
contains garbage data, this may cause problems. For instance,
When doing pull_rt_task(), it may do useless iterations if
rto_mask retains some extra garbage bits. Worse still, this
violates the isolated domain rule for clustered scheduling
using cpuset, because the tasks(with all the cpus allowed)
belongs to one root domain can be pulled away into another
root domain.
The patch cleans the garbage by using zalloc_cpumask_var()
instead of alloc_cpumask_var() for root_domain::rto_mask
allocation, thereby addressing the issues.
Do the same thing for root_domain's other cpumask memembers:
dlo_mask, span, and online.
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1449057179-29321-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Because wakeups can (fundamentally) be late, a task might not be in
the expected state. Therefore testing against a task's state is racy,
and can yield false positives.
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: oleg@redhat.com
Fixes: 9067ac85d5 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task")
Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Consider the following v2 hierarchy.
P0 (+memory) --- P1 (-memory) --- A
\- B
P0 has memory enabled in its subtree_control while P1 doesn't. If
both A and B contain processes, they would belong to the memory css of
P1. Now if memory is enabled on P1's subtree_control, memory csses
should be created on both A and B and A's processes should be moved to
the former and B's processes the latter. IOW, enabling controllers
can cause atomic migrations into different csses.
The core cgroup migration logic has been updated accordingly but the
controller migration methods haven't and still assume that all tasks
migrate to a single target css; furthermore, the methods were fed the
css in which subtree_control was updated which is the parent of the
target csses. pids controller depends on the migration methods to
move charges and this made the controller attribute charges to the
wrong csses often triggering the following warning by driving a
counter negative.
WARNING: CPU: 1 PID: 1 at kernel/cgroup_pids.c:97 pids_cancel.constprop.6+0x31/0x40()
Modules linked in:
CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc1+ #29
...
ffffffff81f65382 ffff88007c043b90 ffffffff81551ffc 0000000000000000
ffff88007c043bc8 ffffffff810de202 ffff88007a752000 ffff88007a29ab00
ffff88007c043c80 ffff88007a1d8400 0000000000000001 ffff88007c043bd8
Call Trace:
[<ffffffff81551ffc>] dump_stack+0x4e/0x82
[<ffffffff810de202>] warn_slowpath_common+0x82/0xc0
[<ffffffff810de2fa>] warn_slowpath_null+0x1a/0x20
[<ffffffff8118e031>] pids_cancel.constprop.6+0x31/0x40
[<ffffffff8118e0fd>] pids_can_attach+0x6d/0xf0
[<ffffffff81188a4c>] cgroup_taskset_migrate+0x6c/0x330
[<ffffffff81188e05>] cgroup_migrate+0xf5/0x190
[<ffffffff81189016>] cgroup_attach_task+0x176/0x200
[<ffffffff8118949d>] __cgroup_procs_write+0x2ad/0x460
[<ffffffff81189684>] cgroup_procs_write+0x14/0x20
[<ffffffff811854e5>] cgroup_file_write+0x35/0x1c0
[<ffffffff812e26f1>] kernfs_fop_write+0x141/0x190
[<ffffffff81265f88>] __vfs_write+0x28/0xe0
[<ffffffff812666fc>] vfs_write+0xac/0x1a0
[<ffffffff81267019>] SyS_write+0x49/0xb0
[<ffffffff81bcef32>] entry_SYSCALL_64_fastpath+0x12/0x76
This patch fixes the bug by removing @css parameter from the three
migration methods, ->can_attach, ->cancel_attach() and ->attach() and
updating cgroup_taskset iteration helpers also return the destination
css in addition to the task being migrated. All controllers are
updated accordingly.
* Controllers which don't care whether there are one or multiple
target csses can be converted trivially. cpu, io, freezer, perf,
netclassid and netprio fall in this category.
* cpuset's current implementation assumes that there's single source
and destination and thus doesn't support v2 hierarchy already. The
only change made by this patchset is how that single destination css
is obtained.
* memory migration path already doesn't do anything on v2. How the
single destination css is obtained is updated and the prep stage of
mem_cgroup_can_attach() is reordered to accomodate the change.
* pids is the only controller which was affected by this bug. It now
correctly handles multi-destination migrations and no longer causes
counter underflow from incorrect accounting.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Pull cgroup updates from Tejun Heo:
"The cgroup core saw several significant updates this cycle:
- percpu_rwsem for threadgroup locking is reinstated. This was
temporarily dropped due to down_write latency issues. Oleg's
rework of percpu_rwsem which is scheduled to be merged in this
merge window resolves the issue.
- On the v2 hierarchy, when controllers are enabled and disabled, all
operations are atomic and can fail and revert cleanly. This allows
->can_attach() failure which is necessary for cpu RT slices.
- Tasks now stay associated with the original cgroups after exit
until released. This allows tracking resources held by zombies
(e.g. pids) and makes it easy to find out where zombies came from
on the v2 hierarchy. The pids controller was broken before these
changes as zombies escaped the limits; unfortunately, updating this
behavior required too many invasive changes and I don't think it's
a good idea to backport them, so the pids controller on 4.3, the
first version which included the pids controller, will stay broken
at least until I'm sure about the cgroup core changes.
- Optimization of a couple common tests using static_key"
* 'for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (38 commits)
cgroup: fix race condition around termination check in css_task_iter_next()
blkcg: don't create "io.stat" on the root cgroup
cgroup: drop cgroup__DEVEL__legacy_files_on_dfl
cgroup: replace error handling in cgroup_init() with WARN_ON()s
cgroup: add cgroup_subsys->free() method and use it to fix pids controller
cgroup: keep zombies associated with their original cgroups
cgroup: make css_set_rwsem a spinlock and rename it to css_set_lock
cgroup: don't hold css_set_rwsem across css task iteration
cgroup: reorganize css_task_iter functions
cgroup: factor out css_set_move_task()
cgroup: keep css_set and task lists in chronological order
cgroup: make cgroup_destroy_locked() test cgroup_is_populated()
cgroup: make css_sets pin the associated cgroups
cgroup: relocate cgroup_[try]get/put()
cgroup: move check_for_release() invocation
cgroup: replace cgroup_has_tasks() with cgroup_is_populated()
cgroup: make cgroup->nr_populated count the number of populated css_sets
cgroup: remove an unused parameter from cgroup_task_migrate()
cgroup: fix too early usage of static_branch_disable()
cgroup: make cgroup_update_dfl_csses() migrate all target processes atomically
...
Pull scheduler changes from Ingo Molnar:
"The main changes in this cycle were:
- sched/fair load tracking fixes and cleanups (Byungchul Park)
- Make load tracking frequency scale invariant (Dietmar Eggemann)
- sched/deadline updates (Juri Lelli)
- stop machine fixes, cleanups and enhancements for bugs triggered by
CPU hotplug stress testing (Oleg Nesterov)
- scheduler preemption code rework: remove PREEMPT_ACTIVE and related
cleanups (Peter Zijlstra)
- Rework the sched_info::run_delay code to fix races (Peter Zijlstra)
- Optimize per entity utilization tracking (Peter Zijlstra)
- ... misc other fixes, cleanups and smaller updates"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
sched: Don't scan all-offline ->cpus_allowed twice if !CONFIG_CPUSETS
sched: Move cpu_active() tests from stop_two_cpus() into migrate_swap_stop()
sched: Start stopper early
stop_machine: Kill cpu_stop_threads->setup() and cpu_stop_unpark()
stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark()
stop_machine: Change cpu_stop_queue_two_works() to rely on stopper->enabled
stop_machine: Introduce __cpu_stop_queue_work() and cpu_stop_queue_two_works()
stop_machine: Ensure that a queued callback will be called before cpu_stop_park()
sched/x86: Fix typo in __switch_to() comments
sched/core: Remove a parameter in the migrate_task_rq() function
sched/core: Drop unlikely behind BUG_ON()
sched/core: Fix task and run queue sched_info::run_delay inconsistencies
sched/numa: Fix task_tick_fair() from disabling numa_balancing
sched/core: Add preempt_count invariant check
sched/core: More notrace annotations
sched/core: Kill PREEMPT_ACTIVE
sched/core, sched/x86: Kill thread_info::saved_preempt_count
sched/core: Simplify preempt_count tests
sched/core: Robustify preemption leak checks
sched/core: Stop setting PREEMPT_ACTIVE
...
If CONFIG_CPUSETS=n then "case cpuset" changes the state and runs
the already failed for_each_cpu() loop again for no reason.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151010185315.GA24100@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpu_active() tests are not fundamentally part of stop_two_cpus(),
move then into the scheduler where they belong.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Ensure the stopper thread is active 'early', because the load balancer
pretty much assumes that its available. And when 'online && active' the
load-balancer is fully available.
Not only the numa balancing stop_two_cpus() caller relies on it, but
also the self migration stuff does, and at CPU_ONLINE time the cpu
really is 'free' to run anything.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151009160054.GA10176@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This reverts:
8cb9764fc8 ("nohz: Set isolcpus when nohz_full is set")
We assumed that full-nohz users always want scheduler isolation on full
dynticks CPUs, therefore we included full-nohz CPUs on cpu_isolated_map.
This means that tasks run by default on CPUs outside the nohz_full range
unless their affinity is explicity overwritten.
This suits pure isolation workloads but when the machine is needed to
run common workloads, the available sets of CPUs to run common tasks
becomes reduced.
We reach an extreme case when CONFIG_NO_HZ_FULL_ALL is enabled as it
leaves only CPU 0 for non-isolation tasks, which makes people think that
their supercomputer regressed to 90's UP - which is true in a sense.
Some full-nohz users appear to be interested in running normal workloads
either before or after an isolation workload. Full-nohz isn't optimized
toward normal workloads but it's still better than UP performance.
We are reaching a limitation in kernel presets here. Lets revert this
cpu_isolated_map inclusion and let userspace do its own scheduler
isolation using cpusets or explicit affinity settings.
Reported-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Link: http://lkml.kernel.org/r/1444663283-30068-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
