Here we add a global radix tree to link memcg and blkcg that the user
attach the tasks to when using cgroup v1, which is used for writeback
cgroup.
Signed-off-by: NJiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

It is unwise to take spin locks from the handlers of trace events.
Mainly, because they can introduce lockups, because it introduces locks
in places that are normally not tested. Worse yet, because trace events
are tucked away in the include/trace/events/ directory, locks that are
taken there are forgotten about.

As a general rule, I tell people never to take any locks in a trace
event handler.

Several cgroup trace event handlers call cgroup_path() which eventually
takes the kernfs_rename_lock spinlock. This injects the spinlock in the
code without people realizing it. It also can cause issues for the
PREEMPT_RT patch, as the spinlock becomes a mutex, and the trace event
handlers are called with preemption disabled.

By moving the calculation of the cgroup_path() out of the trace event
handlers and into a macro (surrounded by a
trace_cgroup_##type##_enabled()), then we could place the cgroup_path
into a string, and pass that to the trace event. Not only does this
remove the taking of the spinlock out of the trace event handler, but
it also means that the cgroup_path() only needs to be called once (it
is currently called twice, once to get the length to reserver the
buffer for, and once again to get the path itself. Now it only needs to
be done once.
Reported-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NTejun Heo <tj@kernel.org>

Variants of proc_create{,_data} that directly take a seq_file show
callback and drastically reduces the boilerplate code in the callers.

All trivial callers converted over.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

cgroup_rstat is being generalized so that controllers can use it too.
This patch factors out and exposes the following interface functions.

* cgroup_rstat_updated(): Renamed from cgroup_rstat_cpu_updated() for
  consistency.

* cgroup_rstat_flush_hold/release(): Factored out from base stat
  implementation.

* cgroup_rstat_flush(): Verbatim expose.

While at it, drop assert on cgroup_rstat_mutex in
cgroup_base_stat_flush() as it crosses layers and make a minor comment
update.

v2: Added EXPORT_SYMBOL_GPL(cgroup_rstat_updated) to fix a build bug.
Signed-off-by: NTejun Heo <tj@kernel.org>

Currently, rstat.c has rstat and base stat implementations intermixed.
Collect base stat implementation at the end of the file.  Also,
reorder the prototypes.

This patch doesn't make any functional changes.
Signed-off-by: NTejun Heo <tj@kernel.org>

Base resource stat accounts universial (not specific to any
controller) resource consumptions on top of rstat.  Currently, its
implementation is intermixed with rstat implementation making the code
confusing to follow.

This patch clarifies the distintion by doing the followings.

* Encapsulate base resource stat counters, currently only cputime, in
  struct cgroup_base_stat.

* Move prev_cputime into struct cgroup and initialize it with cgroup.

* Rename the related functions so that they start with cgroup_base_stat.

* Prefix the related variables and field names with b.

This patch doesn't make any functional changes.
Signed-off-by: NTejun Heo <tj@kernel.org>

stat is too generic a name and ends up causing subtle confusions.
It'll be made generic so that controllers can plug into it, which will
make the problem worse.  Let's rename it to something more specific -
cgroup_rstat for cgroup recursive stat.

This patch does the following renames.  No other changes.

* cpu_stat	-> rstat_cpu
* stat		-> rstat
* ?cstat	-> ?rstatc

Note that the renames are selective.  The unrenamed are the ones which
implement basic resource statistics on top of rstat.  This will be
further cleaned up in the following patches.
Signed-off-by: NTejun Heo <tj@kernel.org>

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NPhilippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The basic cpu stat is currently shown with "cpu." prefix in
cgroup.stat, and the same information is duplicated in cpu.stat when
cpu controller is enabled.  This is ugly and not very scalable as we
want to expand the coverage of stat information which is always
available.

This patch makes cgroup core always create "cpu.stat" file and show
the basic cpu stat there and calls the cpu controller to show the
extra stats when enabled.  This ensures that the same information
isn't presented in multiple places and makes future expansion of basic
stats easier.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>

In cgroup1, while cpuacct isn't actually controlling any resources, it
is a separate controller due to combination of two factors -
1. enabling cpu controller has significant side effects, and 2. we
have to pick one of the hierarchies to account CPU usages on.  cpuacct
controller is effectively used to designate a hierarchy to track CPU
usages on.

cgroup2's unified hierarchy removes the second reason and we can
account basic CPU usages by default.  While we can use cpuacct for
this purpose, both its interface and implementation leave a lot to be
desired - it collects and exposes two sources of truth which don't
agree with each other and some of the exposed statistics don't make
much sense.  Also, it propagates all the way up the hierarchy on each
accounting event which is unnecessary.

This patch adds basic resource accounting mechanism to cgroup2's
unified hierarchy and accounts CPU usages using it.

* All accountings are done per-cpu and don't propagate immediately.
  It just bumps the per-cgroup per-cpu counters and links to the
  parent's updated list if not already on it.

* On a read, the per-cpu counters are collected into the global ones
  and then propagated upwards.  Only the per-cpu counters which have
  changed since the last read are propagated.

* CPU usage stats are collected and shown in "cgroup.stat" with "cpu."
  prefix.  Total usage is collected from scheduling events.  User/sys
  breakdown is sourced from tick sampling and adjusted to the usage
  using cputime_adjust().

This keeps the accounting side hot path O(1) and per-cpu and the read
side O(nr_updated_since_last_read).

v2: Minor changes and documentation updates as suggested by Waiman and
    Roman.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Roman Gushchin <guro@fb.com>

Update debug controller so that it prints out debug info about thread
mode.

 1) The relationship between proc_cset and threaded_csets are displayed.
 2) The status of being a thread root or threaded cgroup is displayed.

This patch is extracted from Waiman's larger patch.

v2: - Removed [thread root] / [threaded] from debug.cgroup_css_links
      file as the same information is available from cgroup.type.
      Suggested by Waiman.
    - Threaded marking is moved to the previous patch.
Patch-originally-by: NWaiman Long <longman@redhat.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

This patch implements cgroup v2 thread support.  The goal of the
thread mode is supporting hierarchical accounting and control at
thread granularity while staying inside the resource domain model
which allows coordination across different resource controllers and
handling of anonymous resource consumptions.

A cgroup is always created as a domain and can be made threaded by
writing to the "cgroup.type" file.  When a cgroup becomes threaded, it
becomes a member of a threaded subtree which is anchored at the
closest ancestor which isn't threaded.

The threads of the processes which are in a threaded subtree can be
placed anywhere without being restricted by process granularity or
no-internal-process constraint.  Note that the threads aren't allowed
to escape to a different threaded subtree.  To be used inside a
threaded subtree, a controller should explicitly support threaded mode
and be able to handle internal competition in the way which is
appropriate for the resource.

The root of a threaded subtree, the nearest ancestor which isn't
threaded, is called the threaded domain and serves as the resource
domain for the whole subtree.  This is the last cgroup where domain
controllers are operational and where all the domain-level resource
consumptions in the subtree are accounted.  This allows threaded
controllers to operate at thread granularity when requested while
staying inside the scope of system-level resource distribution.

As the root cgroup is exempt from the no-internal-process constraint,
it can serve as both a threaded domain and a parent to normal cgroups,
so, unlike non-root cgroups, the root cgroup can have both domain and
threaded children.

Internally, in a threaded subtree, each css_set has its ->dom_cset
pointing to a matching css_set which belongs to the threaded domain.
This ensures that thread root level cgroup_subsys_state for all
threaded controllers are readily accessible for domain-level
operations.

This patch enables threaded mode for the pids and perf_events
controllers.  Neither has to worry about domain-level resource
consumptions and it's enough to simply set the flag.

For more details on the interface and behavior of the thread mode,
please refer to the section 2-2-2 in Documentation/cgroup-v2.txt added
by this patch.

v5: - Dropped silly no-op ->dom_cgrp init from cgroup_create().
      Spotted by Waiman.
    - Documentation updated as suggested by Waiman.
    - cgroup.type content slightly reformatted.
    - Mark the debug controller threaded.

v4: - Updated to the general idea of marking specific cgroups
      domain/threaded as suggested by PeterZ.

v3: - Dropped "join" and always make mixed children join the parent's
      threaded subtree.

v2: - After discussions with Waiman, support for mixed thread mode is
      added.  This should address the issue that Peter pointed out
      where any nesting should be avoided for thread subtrees while
      coexisting with other domain cgroups.
    - Enabling / disabling thread mode now piggy backs on the existing
      control mask update mechanism.
    - Bug fixes and cleanup.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>

Currently, writes "cgroup.procs" and "cgroup.tasks" files are all
handled by __cgroup_procs_write() on both v1 and v2.  This patch
reoragnizes the write path so that there are common helper functions
that different write paths use.

While this somewhat increases LOC, the different paths are no longer
intertwined and each path has more flexibility to implement different
behaviors which will be necessary for the planned v2 thread support.

v3: - Restructured so that cgroup_procs_write_permission() takes
      @src_cgrp and @dst_cgrp.

v2: - Rolled in Waiman's task reference count fix.
    - Updated on top of nsdelegate changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>

Subsystem migration methods shouldn't be called for empty migrations.
cgroup_migrate_execute() implements this guarantee by bailing early if
there are no source css_sets.  This used to be correct before
a79a908f ("cgroup: introduce cgroup namespaces"), but no longer
since the commit because css_sets can stay pinned without tasks in
them.

This caused cgroup_migrate_execute() call into cpuset migration
methods with an empty cgroup_taskset.  cpuset migration methods
correctly assume that cgroup_taskset_first() never returns NULL;
however, due to the bug, it can, leading to the following oops.

  Unable to handle kernel paging request for data at address 0x00000960
  Faulting instruction address: 0xc0000000001d6868
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  CPU: 14 PID: 16947 Comm: kworker/14:0 Tainted: G        W
  4.12.0-rc4-next-20170609 #2
  Workqueue: events cpuset_hotplug_workfn
  task: c00000000ca60580 task.stack: c00000000c728000
  NIP: c0000000001d6868 LR: c0000000001d6858 CTR: c0000000001d6810
  REGS: c00000000c72b720 TRAP: 0300   Tainted: GW (4.12.0-rc4-next-20170609)
  MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 44722422  XER: 20000000
  CFAR: c000000000008710 DAR: 0000000000000960 DSISR: 40000000 SOFTE: 1
  GPR00: c0000000001d6858 c00000000c72b9a0 c000000001536e00 0000000000000000
  GPR04: c00000000c72b9c0 0000000000000000 c00000000c72bad0 c000000766367678
  GPR08: c000000766366d10 c00000000c72b958 c000000001736e00 0000000000000000
  GPR12: c0000000001d6810 c00000000e749300 c000000000123ef8 c000000775af4180
  GPR16: 0000000000000000 0000000000000000 c00000075480e9c0 c00000075480e9e0
  GPR20: c00000075480e8c0 0000000000000001 0000000000000000 c00000000c72ba20
  GPR24: c00000000c72baa0 c00000000c72bac0 c000000001407248 c00000000c72ba20
  GPR28: c00000000141fc80 c00000000c72bac0 c00000000c6bc790 0000000000000000
  NIP [c0000000001d6868] cpuset_can_attach+0x58/0x1b0
  LR [c0000000001d6858] cpuset_can_attach+0x48/0x1b0
  Call Trace:
  [c00000000c72b9a0] [c0000000001d6858] cpuset_can_attach+0x48/0x1b0 (unreliable)
  [c00000000c72ba00] [c0000000001cbe80] cgroup_migrate_execute+0xb0/0x450
  [c00000000c72ba80] [c0000000001d3754] cgroup_transfer_tasks+0x1c4/0x360
  [c00000000c72bba0] [c0000000001d923c] cpuset_hotplug_workfn+0x86c/0xa20
  [c00000000c72bca0] [c00000000011aa44] process_one_work+0x1e4/0x580
  [c00000000c72bd30] [c00000000011ae78] worker_thread+0x98/0x5c0
  [c00000000c72bdc0] [c000000000124058] kthread+0x168/0x1b0
  [c00000000c72be30] [c00000000000b2e8] ret_from_kernel_thread+0x5c/0x74
  Instruction dump:
  f821ffa1 7c7d1b78 60000000 60000000 38810020 7fa3eb78 3f42ffed 4bff4c25
  60000000 3b5a0448 3d420020 eb610020 <e9230960> 7f43d378 e9290000 f92af200
  ---[ end trace dcaaf98fb36d9e64 ]---

This patch fixes the bug by adding an explicit nr_tasks counter to
cgroup_taskset and skipping calling the migration methods if the
counter is zero.  While at it, remove the now spurious check on no
source css_sets.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-and-tested-by: NAbdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: stable@vger.kernel.org # v4.6+
Fixes: a79a908f ("cgroup: introduce cgroup namespaces")
Link: http://lkml.kernel.org/r/1497266622.15415.39.camel@abdul.in.ibm.com

The debug cgroup currently resides within cgroup-v1.c and is enabled
only for v1 cgroup. To enable the debug cgroup also for v2, it makes
sense to put the code into its own file as it will no longer be v1
specific. There is no change to the debug cgroup specific code.
Signed-off-by: NWaiman Long <longman@redhat.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Commit bfb0b80d ("cgroup: avoid attaching a cgroup root to two
different superblocks") is broken.  Now we try to fix the race by
delaying the initialization of cgroup root refcnt until a superblock
has been allocated.
Reported-by: NDmitry Vyukov <dvyukov@google.com>
Reported-by: NAndrei Vagin <avagin@virtuozzo.com>
Tested-by: NAndrei Vagin <avagin@virtuozzo.com>
Signed-off-by: NZefan Li <lizefan@huawei.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: NElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: NHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NDavid Windsor <dwindsor@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Currently, subsys->*attach() callbacks are called for all subsystems
which are attached to the hierarchy on which the migration is taking
place.

With cgroup_migrate_prepare_dst() filtering out identity migrations,
v1 hierarchies can avoid spurious ->*attach() callback invocations
where the source and destination csses are identical; however, this
isn't enough on v2 as only a subset of the attached controllers can be
affected on controller enable/disable.

While spurious ->*attach() invocations aren't critically broken,
they're unnecessary overhead and can lead to temporary overcharges on
certain controllers.  Fix it by tracking which subsystems are affected
by a migration and invoking ->*attach() callbacks only on those
subsystems.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>

cgroup migration is performed in four steps - css_set preloading,
addition of target tasks, actual migration, and clean up.  A list
named preloaded_csets is used to track the preloading.  This is a bit
too restricted and the code is already depending on the subtlety that
all source css_sets appear before destination ones.

Let's create struct cgroup_mgctx which keeps track of everything
during migration.  Currently, it has separate preload lists for source
and destination csets and also embeds cgroup_taskset which is used
during the actual migration.  This moves struct cgroup_taskset
definition to cgroup-internal.h.

This patch doesn't cause any functional changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>

get/put_css_set() get exposed in cgroup-internal.h in the process.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Now that v1 functions are separated out, rename some functions for
consistency.

 cgroup_dfl_base_files		-> cgroup_base_files
 cgroup_legacy_base_files	-> cgroup1_base_files
 cgroup_ssid_no_v1()		-> cgroup1_ssid_disabled()
 cgroup_pidlist_destroy_all	-> cgroup1_pidlist_destroy_all()
 cgroup_release_agent()		-> cgroup1_release_agent()
 check_for_release()		-> cgroup1_check_for_release()
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Now that the v1 mount code is split into separate functions, move them
to kernel/cgroup/cgroup-v1.c along with the mount option handling
code.  As this puts all v1-only kernfs_syscall_ops in cgroup-v1.c,
move cgroup1_kf_syscall_ops to cgroup-v1.c too.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Currently, cgroup_kf_syscall_ops is shared by v1 and v2 and the
specific methods test the version and take different actions.  Split
out v1 functions and put them in cgroup1_kf_syscall_ops and remove the
now unnecessary explicit branches in specific methods.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

cgroup.c is getting too unwieldy.  Let's move out cgroup v1 specific
code along with the debug controller into kernel/cgroup/cgroup-v1.c.

v2: cgroup_mutex and css_set_lock made available in cgroup-internal.h
    regardless of CONFIG_PROVE_RCU.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>