Revert the changes in find_idlest_cpu() and find_idlest_group().
Keep the infrastructure bits which are used in following EAS patches.
Change-Id: Id516ca5f3e51b9a13db1ebb8de2df3aa25f9679b
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
The rate_limit_us tunable is intended to reduce the possible overhead
from running the schedutil governor. However, that overhead can be
divided into two separate parts: the governor computations and the
invocation of the scaling driver to set the CPU frequency. The latter
is where the real overhead comes from. The former is much less
expensive in terms of execution time and running it every time the
governor callback is invoked by the scheduler, after rate_limit_us
interval has passed since the last frequency update, would not be a
problem.
For this reason, redefine the rate_limit_us tunable so that it means the
minimum time that has to pass between two consecutive invocations of the
scaling driver by the schedutil governor (to set the CPU frequency).
Change-Id: Iced64116b826c25441ef537c27a3dabfcf81919e
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[pulled from linux-pm linux-next https://patchwork.kernel.org/patch/9583949/ ]
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
The rate-limit tunable in the schedutil governor applies to transitions
to both lower and higher frequencies. On several platforms it is not the
ideal tunable though, as it is difficult to get best power/performance
figures using the same limit in both directions.
It is common on mobile platforms with demanding user interfaces to want
to increase frequency rapidly for example but decrease slowly.
One of the example can be a case where we have short busy periods
followed by similar or longer idle periods. If we keep the rate-limit
high enough, we will not go to higher frequencies soon enough. On the
other hand, if we keep it too low, we will have too many frequency
transitions, as we will always reduce the frequency after the busy
period.
It would be very useful if we can set low rate-limit while increasing
the frequency (so that we can respond to the short busy periods quickly)
and high rate-limit while decreasing frequency (so that we don't reduce
the frequency immediately after the short busy period and that may avoid
frequency transitions before the next busy period).
Implement separate up/down transition rate limits. Note that the
governor avoids frequency recalculations for a period equal to minimum
of up and down rate-limit. A global mutex is also defined to protect
updates to min_rate_limit_us via two separate sysfs files.
Note that this wouldn't change behavior of the schedutil governor for
the platforms which wish to keep same values for both up and down rate
limits.
This is tested with the rt-app [1] on ARM Exynos, dual A15 processor
platform.
Testcase: Run a SCHED_OTHER thread on CPU0 which will emulate work-load
for X ms of busy period out of the total period of Y ms, i.e. Y - X ms
of idle period. The values of X/Y taken were: 20/40, 20/50, 20/70, i.e
idle periods of 20, 30 and 50 ms respectively. These were tested against
values of up/down rate limits as: 10/10 ms and 10/40 ms.
For every test we noticed a performance increase of 5-10% with the
schedutil governor, which was very much expected.
[Viresh]: Simplified user interface and introduced min_rate_limit_us +
mutex, rewrote commit log and included test results.
[1] https://github.com/scheduler-tools/rt-app/
Change-Id: I18720a83855b196b8e21dcdc8deae79131635b84
Signed-off-by: Steve Muckle <smuckle.linux@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
(applied from https://marc.info/?l=linux-kernel&m=147936011103832&w=2)
[trivial adaptations]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
If WALT is available and enabled, make schedutil governor use its
utilization signal.
Change-Id: I92bc37989447a76616e9bcc4e9e8616774fb9925
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
[we need to use boosted_cpu_util for schedutil, so make it
not static]
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
A policy of going to fmax on any RT activity will be detrimental
for power on many platforms. Often RT accounts for only a small amount
of CPU activity so sending the CPU frequency to fmax is overkill. Worse
still, some platforms may not be able to even complete the CPU frequency
change before the RT activity has already completed.
Cpufreq governors have not treated RT activity this way in the past so
it is not part of the expected semantics of the RT scheduling class. The
DL class offers guarantees about task completion and could be used for
this purpose.
Modify the schedutil algorithm to instead use rt_avg as an estimate of
RT utilization of the CPU.
Based on previous work by Vincent Guittot <vincent.guittot@linaro.org>.
Change-Id: I1ed605a3e2512a94d34217a8e57c3fd97cca60be
Signed-off-by: Steve Muckle <smuckle@linaro.org>
If slow path frequency changes are conducted in a SCHED_OTHER context
then they may be delayed for some amount of time, including
indefinitely, when real time or deadline activity is taking place.
Move the slow path to a real time kernel thread. In the future the
thread should be made SCHED_DEADLINE. The RT priority is arbitrarily set
to 50 for now.
Hackbench results on ARM Exynos, dual core A15 platform for 10
iterations:
$ hackbench -s 100 -l 100 -g 10 -f 20
Before After
---------------------------------
1.808 1.603
1.847 1.251
2.229 1.590
1.952 1.600
1.947 1.257
1.925 1.627
2.694 1.620
1.258 1.621
1.919 1.632
1.250 1.240
Average:
1.8829 1.5041
Based on initial work by Steve Muckle.
Change-Id: I8f53037e94f353960c6d10abf07822d671631ef7
Signed-off-by: Steve Muckle <smuckle.linux@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from 02a7b1ee3b)
[adapt to the 3.18 kthread interface]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
We are going to use kthread workers more widely and sometimes we will need
to make sure that the work is neither pending nor running.
This patch implements cancel_*_sync() operations as inspired by
workqueues. Well, we are synchronized against the other operations via
the worker lock, we use del_timer_sync() and a counter to count parallel
cancel operations. Therefore the implementation might be easier.
First, we check if a worker is assigned. If not, the work has newer been
queued after it was initialized.
Second, we take the worker lock. It must be the right one. The work must
not be assigned to another worker unless it is initialized in between.
Third, we try to cancel the timer when it exists. The timer is deleted
synchronously to make sure that the timer call back is not running. We
need to temporary release the worker->lock to avoid a possible deadlock
with the callback. In the meantime, we set work->canceling counter to
avoid any queuing.
Fourth, we try to remove the work from a worker list. It might be
the list of either normal or delayed works.
Fifth, if the work is running, we call kthread_flush_work(). It might
take an arbitrary time. We need to release the worker-lock again. In the
meantime, we again block any queuing by the canceling counter.
As already mentioned, the check for a pending kthread work is done under a
lock. In compare with workqueues, we do not need to fight for a single
PENDING bit to block other operations. Therefore we do not suffer from
the thundering storm problem and all parallel canceling jobs might use
kthread_flush_work(). Any queuing is blocked until the counter gets zero.
Change-Id: I8a8ece0f93c828f311d0ad5c88d80db2388e4808
Link: http://lkml.kernel.org/r/1470754545-17632-10-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry-picked from 37be45d49d)
[major changes to the original patch while cherry-picking; only rebased
the sync variant]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
The schedfreq governor does not currently handle cpufreq drivers which
use a global set of tunables (!have_governor_per_policy).
For example on x86 and using the acpi cpufreq driver, doing this
cat /sys/devices/system/cpu/cpufreq/sched/up_throttle_nsec
will result in a bad pointer access.
Update the tunable code using the upstream schedutil tunable code by
Rafael Wysocki as a guide.
Includes a partial backport of the reorganized cpufreq tunable
infrastructure.
Change-Id: I7e6f8de1dac297077ad43f37dd2f6ddbfe921c98
Signed-off-by: Steve Muckle <smuckle@linaro.org>
[fixed cherry-pick issue]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
[fixed cherry-pick issue]
Signed-off-by: Thierry Strudel <tstrudel@google.com>
Add a new cpufreq scaling governor, called "schedutil", that uses
scheduler-provided CPU utilization information as input for making
its decisions.
Doing that is possible after commit 34e2c55 (cpufreq: Add
mechanism for registering utilization update callbacks) that
introduced cpufreq_update_util() called by the scheduler on
utilization changes (from CFS) and RT/DL task status updates.
In particular, CPU frequency scaling decisions may be based on
the the utilization data passed to cpufreq_update_util() by CFS.
The new governor is relatively simple.
The frequency selection formula used by it depends on whether or not
the utilization is frequency-invariant. In the frequency-invariant
case the new CPU frequency is given by
next_freq = 1.25 * max_freq * util / max
where util and max are the last two arguments of cpufreq_update_util().
In turn, if util is not frequency-invariant, the maximum frequency in
the above formula is replaced with the current frequency of the CPU:
next_freq = 1.25 * curr_freq * util / max
The coefficient 1.25 corresponds to the frequency tipping point at
(util / max) = 0.8.
All of the computations are carried out in the utilization update
handlers provided by the new governor. One of those handlers is
used for cpufreq policies shared between multiple CPUs and the other
one is for policies with one CPU only (and therefore it doesn't need
to use any extra synchronization means).
The governor supports fast frequency switching if that is supported
by the cpufreq driver in use and possible for the given policy.
In the fast switching case, all operations of the governor take
place in its utilization update handlers. If fast switching cannot
be used, the frequency switch operations are carried out with the
help of a work item which only calls __cpufreq_driver_target()
(under a mutex) to trigger a frequency update (to a value already
computed beforehand in one of the utilization update handlers).
Currently, the governor treats all of the RT and DL tasks as
"unknown utilization" and sets the frequency to the allowed
maximum when updated from the RT or DL sched classes. That
heavy-handed approach should be replaced with something more
subtle and specifically targeted at RT and DL tasks.
The governor shares some tunables management code with the
"ondemand" and "conservative" governors and uses some common
definitions from cpufreq_governor.h, but apart from that it
is stand-alone.
Change-Id: I03876e622768e4b3ee4dc28682af7cce771f2f4c
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
(cherry-picked from 9bdcb44e39)
[ Backport the schedutil cpufreq governor from 4.9. Some cpufreq
tunable infrastructure as well as the resolve_freq API is also
backported as those are dependencies]
Signed-off-by: Steve Muckle <smuckle@linaro.org>
[trivial cherry-picking fixes]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
[fixed default governor machinery]
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
The scheduler cpufreq hooks are required by the schedutil cpufreq
governor.
Change-Id: Ied6c46262bb33b7e81bbb3d3d2761124e0c676b7
Signed-off-by: Steve Muckle <smuckle@linaro.org>
[trivial cherry-picking fixes]
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
commit 30e7d894c1 upstream.
Enabling the tracer selftest triggers occasionally the warning in
text_poke(), which warns when the to be modified page is not marked
reserved.
The reason is that the tracer selftest installs kprobes on functions marked
__init for testing. These probes are removed after the tests, but that
removal schedules the delayed kprobes_optimizer work, which will do the
actual text poke. If the work is executed after the init text is freed,
then the warning triggers. The bug can be reproduced reliably when the work
delay is increased.
Flush the optimizer work and wait for the optimizing/unoptimizing lists to
become empty before returning from the kprobes tracer selftest. That
ensures that all operations which were queued due to the probes removal
have completed.
Link: http://lkml.kernel.org/r/20170516094802.76a468bb@gandalf.local.home
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 6274de498 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 2c4569ca26 upstream.
irq_set_chained_handler_and_data() sets up the chained interrupt and then
stores the handler data.
That's racy against an immediate interrupt which gets handled before the
store of the handler data happened. The handler will dereference a NULL
pointer and crash.
Cure it by storing handler data before installing the chained handler.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 3fd3722621 upstream.
Imagine we have a pid namespace and a task from its parent's pid_ns,
which made setns() to the pid namespace. The task is doing fork(),
while the pid namespace's child reaper is dying. We have the race
between them:
Task from parent pid_ns Child reaper
copy_process() ..
alloc_pid() ..
.. zap_pid_ns_processes()
.. disable_pid_allocation()
.. read_lock(&tasklist_lock)
.. iterate over pids in pid_ns
.. kill tasks linked to pids
.. read_unlock(&tasklist_lock)
write_lock_irq(&tasklist_lock); ..
attach_pid(p, PIDTYPE_PID); ..
.. ..
So, just created task p won't receive SIGKILL signal,
and the pid namespace will be in contradictory state.
Only manual kill will help there, but does the userspace
care about this? I suppose, the most users just inject
a task into a pid namespace and wait a SIGCHLD from it.
The patch fixes the problem. It simply checks for
(pid_ns->nr_hashed & PIDNS_HASH_ADDING) in copy_process().
We do it under the tasklist_lock, and can't skip
PIDNS_HASH_ADDING as noted by Oleg:
"zap_pid_ns_processes() does disable_pid_allocation()
and then takes tasklist_lock to kill the whole namespace.
Given that copy_process() checks PIDNS_HASH_ADDING
under write_lock(tasklist) they can't race;
if copy_process() takes this lock first, the new child will
be killed, otherwise copy_process() can't miss
the change in ->nr_hashed."
If allocation is disabled, we just return -ENOMEM
like it's made for such cases in alloc_pid().
v2: Do not move disable_pid_allocation(), do not
introduce a new variable in copy_process() and simplify
the patch as suggested by Oleg Nesterov.
Account the problem with double irq enabling
found by Eric W. Biederman.
Fixes: c876ad7682 ("pidns: Stop pid allocation when init dies")
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Mike Rapoport <rppt@linux.vnet.ibm.com>
CC: Michal Hocko <mhocko@suse.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: "Eric W. Biederman" <ebiederm@xmission.com>
CC: Andrei Vagin <avagin@openvz.org>
CC: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Serge Hallyn <serge@hallyn.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit b9a985db98 upstream.
The code can potentially sleep for an indefinite amount of time in
zap_pid_ns_processes triggering the hung task timeout, and increasing
the system average. This is undesirable. Sleep with a task state of
TASK_INTERRUPTIBLE instead of TASK_UNINTERRUPTIBLE to remove these
undesirable side effects.
Apparently under heavy load this has been allowing Chrome to trigger
the hung time task timeout error and cause ChromeOS to reboot.
Reported-by: Vovo Yang <vovoy@google.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 6347e90091 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 07a77929ba upstream.
The author meant to free the variable that was just allocated, instead
of the one that failed to be allocated, but made a simple typo. This
patch rectifies that.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit ea00f4f4f0)
This makes pm notifier PREPARE/POST symmetrical: if PREPARE
fails, we will only undo what ever happened on PREPARE.
It fixes the unbalanced CPU hotplug enable in CPU PM notifier.
Change-Id: I01dce3cc95c5d6b8913b7b6be301f2909258c745
Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
commit 321027c1fe upstream.
Di Shen reported a race between two concurrent sys_perf_event_open()
calls where both try and move the same pre-existing software group
into a hardware context.
The problem is exactly that described in commit:
f63a8daa58 ("perf: Fix event->ctx locking")
... where, while we wait for a ctx->mutex acquisition, the event->ctx
relation can have changed under us.
That very same commit failed to recognise sys_perf_event_context() as an
external access vector to the events and thereby didn't apply the
established locking rules correctly.
So while one sys_perf_event_open() call is stuck waiting on
mutex_lock_double(), the other (which owns said locks) moves the group
about. So by the time the former sys_perf_event_open() acquires the
locks, the context we've acquired is stale (and possibly dead).
Apply the established locking rules as per perf_event_ctx_lock_nested()
to the mutex_lock_double() for the 'move_group' case. This obviously means
we need to validate state after we acquire the locks.
Reported-by: Di Shen (Keen Lab)
Tested-by: John Dias <joaodias@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Min Chong <mchong@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: f63a8daa58 ("perf: Fix event->ctx locking")
Link: http://lkml.kernel.org/r/20170106131444.GZ3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 4.4:
- Test perf_event::group_flags instead of group_caps
- Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit d29216842a upstream.
CAI Qian <caiqian@redhat.com> pointed out that the semantics
of shared subtrees make it possible to create an exponentially
increasing number of mounts in a mount namespace.
mkdir /tmp/1 /tmp/2
mount --make-rshared /
for i in $(seq 1 20) ; do mount --bind /tmp/1 /tmp/2 ; done
Will create create 2^20 or 1048576 mounts, which is a practical problem
as some people have managed to hit this by accident.
As such CVE-2016-6213 was assigned.
Ian Kent <raven@themaw.net> described the situation for autofs users
as follows:
> The number of mounts for direct mount maps is usually not very large because of
> the way they are implemented, large direct mount maps can have performance
> problems. There can be anywhere from a few (likely case a few hundred) to less
> than 10000, plus mounts that have been triggered and not yet expired.
>
> Indirect mounts have one autofs mount at the root plus the number of mounts that
> have been triggered and not yet expired.
>
> The number of autofs indirect map entries can range from a few to the common
> case of several thousand and in rare cases up to between 30000 and 50000. I've
> not heard of people with maps larger than 50000 entries.
>
> The larger the number of map entries the greater the possibility for a large
> number of active mounts so it's not hard to expect cases of a 1000 or somewhat
> more active mounts.
So I am setting the default number of mounts allowed per mount
namespace at 100,000. This is more than enough for any use case I
know of, but small enough to quickly stop an exponential increase
in mounts. Which should be perfect to catch misconfigurations and
malfunctioning programs.
For anyone who needs a higher limit this can be changed by writing
to the new /proc/sys/fs/mount-max sysctl.
Tested-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 78f7a45dac upstream.
I noticed that reading the snapshot file when it is empty no longer gives a
status. It suppose to show the status of the snapshot buffer as well as how
to allocate and use it. For example:
># cat snapshot
# tracer: nop
#
#
# * Snapshot is allocated *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
# Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
# (Doesn't have to be '2' works with any number that
# is not a '0' or '1')
But instead it just showed an empty buffer:
># cat snapshot
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:4
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
What happened was that it was using the ring_buffer_iter_empty() function to
see if it was empty, and if it was, it showed the status. But that function
was returning false when it was empty. The reason was that the iter header
page was on the reader page, and the reader page was empty, but so was the
buffer itself. The check only tested to see if the iter was on the commit
page, but the commit page was no longer pointing to the reader page, but as
all pages were empty, the buffer is also.
Fixes: 651e22f270 ("ring-buffer: Always reset iterator to reader page")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit df62db5be2 upstream.
Currently the snapshot trigger enables the probe and then allocates the
snapshot. If the probe triggers before the allocation, it could cause the
snapshot to fail and turn tracing off. It's best to allocate the snapshot
buffer first, and then enable the trigger. If something goes wrong in the
enabling of the trigger, the snapshot buffer is still allocated, but it can
also be freed by the user by writting zero into the snapshot buffer file.
Also add a check of the return status of alloc_snapshot().
Fixes: 77fd5c15e3 ("tracing: Add snapshot trigger to function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 77f88796ce upstream.
Creation of a kthread goes through a couple interlocked stages between
the kthread itself and its creator. Once the new kthread starts
running, it initializes itself and wakes up the creator. The creator
then can further configure the kthread and then let it start doing its
job by waking it up.
In this configuration-by-creator stage, the creator is the only one
that can wake it up but the kthread is visible to userland. When
altering the kthread's attributes from userland is allowed, this is
fine; however, for cases where CPU affinity is critical,
kthread_bind() is used to first disable affinity changes from userland
and then set the affinity. This also prevents the kthread from being
migrated into non-root cgroups as that can affect the CPU affinity and
many other things.
Unfortunately, the cgroup side of protection is racy. While the
PF_NO_SETAFFINITY flag prevents further migrations, userland can win
the race before the creator sets the flag with kthread_bind() and put
the kthread in a non-root cgroup, which can lead to all sorts of
problems including incorrect CPU affinity and starvation.
This bug got triggered by userland which periodically tries to migrate
all processes in the root cpuset cgroup to a non-root one. Per-cpu
workqueue workers got caught while being created and ended up with
incorrected CPU affinity breaking concurrency management and sometimes
stalling workqueue execution.
This patch adds task->no_cgroup_migration which disallows the task to
be migrated by userland. kthreadd starts with the flag set making
every child kthread start in the root cgroup with migration
disallowed. The flag is cleared after the kthread finishes
initialization by which time PF_NO_SETAFFINITY is set if the kthread
should stay in the root cgroup.
It'd be better to wait for the initialization instead of failing but I
couldn't think of a way of implementing that without adding either a
new PF flag, or sleeping and retrying from waiting side. Even if
userland depends on changing cgroup membership of a kthread, it either
has to be synchronized with kthread_create() or periodically repeat,
so it's unlikely that this would break anything.
v2: Switch to a simpler implementation using a new task_struct bit
field suggested by Oleg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-and-debugged-by: Chris Mason <clm@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 5402e97af6 upstream.
In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against
__TASK_TRACED. If this races with the ptrace_unfreeze_traced at the end
of a PTRACE_LISTEN, this can wake the task /after/ the check against
__TASK_TRACED, but before the reset of state to TASK_TRACED. This
causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup
against TRACED while the task is still on the rq wake_list, corrupting
it.
Oleg said:
"The kernel can crash or this can lead to other hard-to-debug problems.
In short, "task->state = TASK_TRACED" in ptrace_unfreeze_traced()
assumes that nobody else can wake it up, but PTRACE_LISTEN breaks the
contract. Obviusly it is very wrong to manipulate task->state if this
task is already running, or WAKING, or it sleeps again"
[akpm@linux-foundation.org: coding-style fixes]
Fixes: 9899d11f ("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL")
Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com
Signed-off-by: Ben Segall <bsegall@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
EAS uses "const struct sched_group_energy * const" fairly consistently.
But a couple of places swap the "*" and second "const", making the
pointer mutable.
In the case of struct sched_group, "* const" would have been an error,
since init_sched_energy() writes to sd->groups->sge.
Change-Id: Ic6a8fcf99e65c0f25d9cc55c32625ef3ca5c9aca
Signed-off-by: Greg Hackmann <ghackmann@google.com>
commit de5540d088 upstream.
Under extremely heavy uses of padata, crashes occur, and with list
debugging turned on, this happens instead:
[87487.298728] WARNING: CPU: 1 PID: 882 at lib/list_debug.c:33
__list_add+0xae/0x130
[87487.301868] list_add corruption. prev->next should be next
(ffffb17abfc043d0), but was ffff8dba70872c80. (prev=ffff8dba70872b00).
[87487.339011] [<ffffffff9a53d075>] dump_stack+0x68/0xa3
[87487.342198] [<ffffffff99e119a1>] ? console_unlock+0x281/0x6d0
[87487.345364] [<ffffffff99d6b91f>] __warn+0xff/0x140
[87487.348513] [<ffffffff99d6b9aa>] warn_slowpath_fmt+0x4a/0x50
[87487.351659] [<ffffffff9a58b5de>] __list_add+0xae/0x130
[87487.354772] [<ffffffff9add5094>] ? _raw_spin_lock+0x64/0x70
[87487.357915] [<ffffffff99eefd66>] padata_reorder+0x1e6/0x420
[87487.361084] [<ffffffff99ef0055>] padata_do_serial+0xa5/0x120
padata_reorder calls list_add_tail with the list to which its adding
locked, which seems correct:
spin_lock(&squeue->serial.lock);
list_add_tail(&padata->list, &squeue->serial.list);
spin_unlock(&squeue->serial.lock);
This therefore leaves only place where such inconsistency could occur:
if padata->list is added at the same time on two different threads.
This pdata pointer comes from the function call to
padata_get_next(pd), which has in it the following block:
next_queue = per_cpu_ptr(pd->pqueue, cpu);
padata = NULL;
reorder = &next_queue->reorder;
if (!list_empty(&reorder->list)) {
padata = list_entry(reorder->list.next,
struct padata_priv, list);
spin_lock(&reorder->lock);
list_del_init(&padata->list);
atomic_dec(&pd->reorder_objects);
spin_unlock(&reorder->lock);
pd->processed++;
goto out;
}
out:
return padata;
I strongly suspect that the problem here is that two threads can race
on reorder list. Even though the deletion is locked, call to
list_entry is not locked, which means it's feasible that two threads
pick up the same padata object and subsequently call list_add_tail on
them at the same time. The fix is thus be hoist that lock outside of
that block.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 619bd4a718 upstream.
Since the change in commit:
fd7a4bed18 ("sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks")
... we don't reschedule a task under certain circumstances:
Lets say task-A, SCHED_OTHER, is running on CPU0 (and it may run only on
CPU0) and holds a PI lock. This task is removed from the CPU because it
used up its time slice and another SCHED_OTHER task is running. Task-B on
CPU1 runs at RT priority and asks for the lock owned by task-A. This
results in a priority boost for task-A. Task-B goes to sleep until the
lock has been made available. Task-A is already runnable (but not active),
so it receives no wake up.
The reality now is that task-A gets on the CPU once the scheduler decides
to remove the current task despite the fact that a high priority task is
enqueued and waiting. This may take a long time.
The desired behaviour is that CPU0 immediately reschedules after the
priority boost which made task-A the task with the lowest priority.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: fd7a4bed18 ("sched, rt: Convert switched_{from, to}_rt() prio_changed_rt() to balance callbacks")
Link: http://lkml.kernel.org/r/20170124144006.29821-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
