The static usage pattern of creating a cgroup, enabling controllers,
and then seeding it with CLONE_INTO_CGROUP doesn't require write
locking cgroup_threadgroup_rwsem and thus doesn't benefit from this
patch.

To avoid affecting other users, the per threadgroup rwsem is only used
when the favordynmods is enabled.

As computer hardware advances, modern systems are typically equipped
with many CPU cores and large amounts of memory, enabling the deployment
of numerous applications. On such systems, container creation and
deletion become frequent operations, making cgroup process migration no
longer a cold path. This leads to noticeable contention with common
process operations such as fork, exec, and exit.

To alleviate the contention between cgroup process migration and
operations like process fork, this patch modifies lock to take the write
lock on signal_struct->group_rwsem when writing pid to
cgroup.procs/threads instead of holding a global write lock.

Cgroup process migration has historically relied on
signal_struct->group_rwsem to protect thread group integrity. In commit
<1ed1328792ff> ("sched, cgroup: replace signal_struct->group_rwsem with
a global percpu_rwsem"), this was changed to a global
cgroup_threadgroup_rwsem. The advantage of using a global lock was
simplified handling of process group migrations. This patch retains the
use of the global lock for protecting process group migration, while
reducing contention by using per thread group lock during
cgroup.procs/threads writes.

The locking behavior is as follows:

write cgroup.procs/threads  | process fork,exec,exit | process group migration
------------------------------------------------------------------------------
cgroup_lock()               | down_read(&g_rwsem)    | cgroup_lock()
down_write(&p_rwsem)        | down_read(&p_rwsem)    | down_write(&g_rwsem)
critical section            | critical section       | critical section
up_write(&p_rwsem)          | up_read(&p_rwsem)      | up_write(&g_rwsem)
cgroup_unlock()             | up_read(&g_rwsem)      | cgroup_unlock()

g_rwsem denotes cgroup_threadgroup_rwsem, p_rwsem denotes
signal_struct->group_rwsem.

This patch eliminates contention between cgroup migration and fork
operations for threads that belong to different thread groups, thereby
reducing the long-tail latency of cgroup migrations and lowering system
load.

With this patch, under heavy fork and exec interference, the long-tail
latency of cgroup migration has been reduced from milliseconds to
microseconds. Under heavy cgroup migration interference, the multi-CPU
score of the spawn test case in UnixBench increased by 9%.

tj: Update comment in cgroup_favor_dynmods() and switch WARN_ONCE() to
    pr_warn_once().

Signed-off-by: Yi Tao <escape@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

To prepare for handling posix timer signals on sigaction(SIG_IGN) properly,
add a list to task::signal.

This list will be used to queue posix timers so their signal can be
requeued when SIG_IGN is lifted later.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.920101900@linutronix.de

Pull sched_ext support from Tejun Heo:
 "This implements a new scheduler class called ‘ext_sched_class’, or
  sched_ext, which allows scheduling policies to be implemented as BPF
  programs.

  The goals of this are:

   - Ease of experimentation and exploration: Enabling rapid iteration
     of new scheduling policies.

   - Customization: Building application-specific schedulers which
     implement policies that are not applicable to general-purpose
     schedulers.

   - Rapid scheduler deployments: Non-disruptive swap outs of scheduling
     policies in production environments"

See individual commits for more documentation, but also the cover letter
for the latest series:

Link: https://lore.kernel.org/all/20240618212056.2833381-1-tj@kernel.org/

* tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (110 commits)
  sched: Move update_other_load_avgs() to kernel/sched/pelt.c
  sched_ext: Don't trigger ops.quiescent/runnable() on migrations
  sched_ext: Synchronize bypass state changes with rq lock
  scx_qmap: Implement highpri boosting
  sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()
  sched_ext: Compact struct bpf_iter_scx_dsq_kern
  sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq()
  sched_ext: Move consume_local_task() upward
  sched_ext: Move sanity check and dsq_mod_nr() into task_unlink_from_dsq()
  sched_ext: Reorder args for consume_local/remote_task()
  sched_ext: Restructure dispatch_to_local_dsq()
  sched_ext: Fix processs_ddsp_deferred_locals() by unifying DTL_INVALID handling
  sched_ext: Make find_dsq_for_dispatch() handle SCX_DSQ_LOCAL_ON
  sched_ext: Refactor consume_remote_task()
  sched_ext: Rename scx_kfunc_set_sleepable to unlocked and relocate
  sched_ext: Add missing static to scx_dump_data
  sched_ext: Add missing static to scx_has_op[]
  sched_ext: Temporarily work around pick_task_scx() being called without balance_scx()
  sched_ext: Add a cgroup scheduler which uses flattened hierarchy
  sched_ext: Add cgroup support
  ...

No requirement for a real list. Spare a few bytes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

struct scx_dsq_node contains two data structure nodes to link the containing
task to a DSQ and a flags field that is protected by the lock of the
associated DSQ. One reason why they are grouped into a struct is to use the
type independently as a cursor node when iterating tasks on a DSQ. However,
when iterating, the cursor only needs to be linked on the FIFO list and the
rb_node part ends up inflating the size of the iterator data structure
unnecessarily making it potentially too expensive to place it on stack.

Take ->priq and ->flags out of scx_dsq_node and put them in sched_ext_entity
as ->dsq_priq and ->dsq_flags, respectively. scx_dsq_node is renamed to
scx_dsq_list_node and the field names are renamed accordingly. This will
help implementing DSQ task iterator that can be allocated on stack.

No functional change intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: David Vernet <void@manifault.com>

Currently, a dsq is always a FIFO. A task which is dispatched earlier gets
consumed or executed earlier. While this is sufficient when dsq's are used
for simple staging areas for tasks which are ready to execute, it'd make
dsq's a lot more useful if they can implement custom ordering.

This patch adds a vtime-ordered priority queue to dsq's. When the BPF
scheduler dispatches a task with the new scx_bpf_dispatch_vtime() helper, it
can specify the vtime tha the task should be inserted at and the task is
inserted into the priority queue in the dsq which is ordered according to
time_before64() comparison of the vtime values.

A DSQ can either be a FIFO or priority queue and automatically switches
between the two depending on whether scx_bpf_dispatch() or
scx_bpf_dispatch_vtime() is used. Using the wrong variant while the DSQ
already has the other type queued is not allowed and triggers an ops error.
Built-in DSQs must always be FIFOs.

This makes it very easy for the BPF schedulers to implement proper vtime
based scheduling within each dsq very easy and efficient at a negligible
cost in terms of code complexity and overhead.

scx_simple and scx_example_flatcg are updated to default to weighted
vtime scheduling (the latter within each cgroup). FIFO scheduling can be
selected with -f option.

v4: - As allowing mixing priority queue and FIFO on the same DSQ sometimes
      led to unexpected starvations, DSQs now error out if both modes are
      used at the same time and the built-in DSQs are no longer allowed to
      be priority queues.

    - Explicit type struct scx_dsq_node added to contain fields needed to be
      linked on DSQs. This will be used to implement stateful iterator.

    - Tasks are now always linked on dsq->list whether the DSQ is in FIFO or
      PRIQ mode. This confines PRIQ related complexities to the enqueue and
      dequeue paths. Other paths only need to look at dsq->list. This will
      also ease implementing BPF iterator.

    - Print p->scx.dsq_flags in debug dump.

v3: - SCX_TASK_DSQ_ON_PRIQ flag is moved from p->scx.flags into its own
      p->scx.dsq_flags. The flag is protected with the dsq lock unlike other
      flags in p->scx.flags. This led to flag corruption in some cases.

    - Add comments explaining the interaction between using consumption of
      p->scx.slice to determine vtime progress and yielding.

v2: - p->scx.dsq_vtime was not initialized on load or across cgroup
      migrations leading to some tasks being stalled for extended period of
      time depending on how saturated the machine is. Fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>

The most common and critical way that a BPF scheduler can misbehave is by
failing to run runnable tasks for too long. This patch implements a
watchdog.

* All tasks record when they become runnable.

* A watchdog work periodically scans all runnable tasks. If any task has
  stayed runnable for too long, the BPF scheduler is aborted.

* scheduler_tick() monitors whether the watchdog itself is stuck. If so, the
  BPF scheduler is aborted.

Because the watchdog only scans the tasks which are currently runnable and
usually very infrequently, the overhead should be negligible.
scx_qmap is updated so that it can be told to stall user and/or
kernel tasks.

A detected task stall looks like the following:

 sched_ext: BPF scheduler "qmap" errored, disabling
 sched_ext: runnable task stall (dbus-daemon[953] failed to run for 6.478s)
    scx_check_timeout_workfn+0x10e/0x1b0
    process_one_work+0x287/0x560
    worker_thread+0x234/0x420
    kthread+0xe9/0x100
    ret_from_fork+0x1f/0x30

A detected watchdog stall:

 sched_ext: BPF scheduler "qmap" errored, disabling
 sched_ext: runnable task stall (watchdog failed to check in for 5.001s)
    scheduler_tick+0x2eb/0x340
    update_process_times+0x7a/0x90
    tick_sched_timer+0xd8/0x130
    __hrtimer_run_queues+0x178/0x3b0
    hrtimer_interrupt+0xfc/0x390
    __sysvec_apic_timer_interrupt+0xb7/0x2b0
    sysvec_apic_timer_interrupt+0x90/0xb0
    asm_sysvec_apic_timer_interrupt+0x1b/0x20
    default_idle+0x14/0x20
    arch_cpu_idle+0xf/0x20
    default_idle_call+0x50/0x90
    do_idle+0xe8/0x240
    cpu_startup_entry+0x1d/0x20
    kernel_init+0x0/0x190
    start_kernel+0x0/0x392
    start_kernel+0x324/0x392
    x86_64_start_reservations+0x2a/0x2c
    x86_64_start_kernel+0x104/0x109
    secondary_startup_64_no_verify+0xce/0xdb

Note that this patch exposes scx_ops_error[_type]() in kernel/sched/ext.h to
inline scx_notify_sched_tick().

v4: - While disabling, cancel_delayed_work_sync(&scx_watchdog_work) was
      being called before forward progress was guaranteed and thus could
      lead to system lockup. Relocated.

    - While enabling, it was comparing msecs against jiffies without
      conversion leading to spurious load failures on lower HZ kernels.
      Fixed.

    - runnable list management is now used by core bypass logic and moved to
      the patch implementing sched_ext core.

v3: - bpf_scx_init_member() was incorrectly comparing ops->timeout_ms
      against SCX_WATCHDOG_MAX_TIMEOUT which is in jiffies without
      conversion leading to spurious load failures in lower HZ kernels.
      Fixed.

v2: - Julia Lawall noticed that the watchdog code was mixing msecs and
      jiffies. Fix by using jiffies for everything.

Signed-off-by: David Vernet <dvernet@meta.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
Cc: Julia Lawall <julia.lawall@inria.fr>

Implement a new scheduler class sched_ext (SCX), which allows scheduling
policies to be implemented as BPF programs to achieve the following:

1. Ease of experimentation and exploration: Enabling rapid iteration of new
   scheduling policies.

2. Customization: Building application-specific schedulers which implement
   policies that are not applicable to general-purpose schedulers.

3. Rapid scheduler deployments: Non-disruptive swap outs of scheduling
   policies in production environments.

sched_ext leverages BPF’s struct_ops feature to define a structure which
exports function callbacks and flags to BPF programs that wish to implement
scheduling policies. The struct_ops structure exported by sched_ext is
struct sched_ext_ops, and is conceptually similar to struct sched_class. The
role of sched_ext is to map the complex sched_class callbacks to the more
simple and ergonomic struct sched_ext_ops callbacks.

For more detailed discussion on the motivations and overview, please refer
to the cover letter.

Later patches will also add several example schedulers and documentation.

This patch implements the minimum core framework to enable implementation of
BPF schedulers. Subsequent patches will gradually add functionalities
including safety guarantee mechanisms, nohz and cgroup support.

include/linux/sched/ext.h defines struct sched_ext_ops. With the comment on
top, each operation should be self-explanatory. The followings are worth
noting:

- Both "sched_ext" and its shorthand "scx" are used. If the identifier
  already has "sched" in it, "ext" is used; otherwise, "scx".

- In sched_ext_ops, only .name is mandatory. Every operation is optional and
  if omitted a simple but functional default behavior is provided.

- A new policy constant SCHED_EXT is added and a task can select sched_ext
  by invoking sched_setscheduler(2) with the new policy constant. However,
  if the BPF scheduler is not loaded, SCHED_EXT is the same as SCHED_NORMAL
  and the task is scheduled by CFS. When the BPF scheduler is loaded, all
  tasks which have the SCHED_EXT policy are switched to sched_ext.

- To bridge the workflow imbalance between the scheduler core and
  sched_ext_ops callbacks, sched_ext uses simple FIFOs called dispatch
  queues (dsq's). By default, there is one global dsq (SCX_DSQ_GLOBAL), and
  one local per-CPU dsq (SCX_DSQ_LOCAL). SCX_DSQ_GLOBAL is provided for
  convenience and need not be used by a scheduler that doesn't require it.
  SCX_DSQ_LOCAL is the per-CPU FIFO that sched_ext pulls from when putting
  the next task on the CPU. The BPF scheduler can manage an arbitrary number
  of dsq's using scx_bpf_create_dsq() and scx_bpf_destroy_dsq().

- sched_ext guarantees system integrity no matter what the BPF scheduler
  does. To enable this, each task's ownership is tracked through
  p->scx.ops_state and all tasks are put on scx_tasks list. The disable path
  can always recover and revert all tasks back to CFS. See p->scx.ops_state
  and scx_tasks.

- A task is not tied to its rq while enqueued. This decouples CPU selection
  from queueing and allows sharing a scheduling queue across an arbitrary
  subset of CPUs. This adds some complexities as a task may need to be
  bounced between rq's right before it starts executing. See
  dispatch_to_local_dsq() and move_task_to_local_dsq().

- One complication that arises from the above weak association between task
  and rq is that synchronizing with dequeue() gets complicated as dequeue()
  may happen anytime while the task is enqueued and the dispatch path might
  need to release the rq lock to transfer the task. Solving this requires a
  bit of complexity. See the logic around p->scx.sticky_cpu and
  p->scx.ops_qseq.

- Both enable and disable paths are a bit complicated. The enable path
  switches all tasks without blocking to avoid issues which can arise from
  partially switched states (e.g. the switching task itself being starved).
  The disable path can't trust the BPF scheduler at all, so it also has to
  guarantee forward progress without blocking. See scx_ops_enable() and
  scx_ops_disable_workfn().

- When sched_ext is disabled, static_branches are used to shut down the
  entry points from hot paths.

v7: - scx_ops_bypass() was incorrectly and unnecessarily trying to grab
      scx_ops_enable_mutex which can lead to deadlocks in the disable path.
      Fixed.

    - Fixed TASK_DEAD handling bug in scx_ops_enable() path which could lead
      to use-after-free.

    - Consolidated per-cpu variable usages and other cleanups.

v6: - SCX_NR_ONLINE_OPS replaced with SCX_OPI_*_BEGIN/END so that multiple
      groups can be expressed. Later CPU hotplug operations are put into
      their own group.

    - SCX_OPS_DISABLING state is replaced with the new bypass mechanism
      which allows temporarily putting the system into simple FIFO
      scheduling mode bypassing the BPF scheduler. In addition to the shut
      down path, this will also be used to isolate the BPF scheduler across
      PM events. Enabling and disabling the bypass mode requires iterating
      all runnable tasks. rq->scx.runnable_list addition is moved from the
      later watchdog patch.

    - ops.prep_enable() is replaced with ops.init_task() and
      ops.enable/disable() are now called whenever the task enters and
      leaves sched_ext instead of when the task becomes schedulable on
      sched_ext and stops being so. A new operation - ops.exit_task() - is
      called when the task stops being schedulable on sched_ext.

    - scx_bpf_dispatch() can now be called from ops.select_cpu() too. This
      removes the need for communicating local dispatch decision made by
      ops.select_cpu() to ops.enqueue() via per-task storage.
      SCX_KF_SELECT_CPU is added to support the change.

    - SCX_TASK_ENQ_LOCAL which told the BPF scheudler that
      scx_select_cpu_dfl() wants the task to be dispatched to the local DSQ
      was removed. Instead, scx_bpf_select_cpu_dfl() now dispatches directly
      if it finds a suitable idle CPU. If such behavior is not desired,
      users can use scx_bpf_select_cpu_dfl() which returns the verdict in a
      bool out param.

    - scx_select_cpu_dfl() was mishandling WAKE_SYNC and could end up
      queueing many tasks on a local DSQ which makes tasks to execute in
      order while other CPUs stay idle which made some hackbench numbers
      really bad. Fixed.

    - The current state of sched_ext can now be monitored through files
      under /sys/sched_ext instead of /sys/kernel/debug/sched/ext. This is
      to enable monitoring on kernels which don't enable debugfs.

    - sched_ext wasn't telling BPF that ops.dispatch()'s @prev argument may
      be NULL and a BPF scheduler which derefs the pointer without checking
      could crash the kernel. Tell BPF. This is currently a bit ugly. A
      better way to annotate this is expected in the future.

    - scx_exit_info updated to carry pointers to message buffers instead of
      embedding them directly. This decouples buffer sizes from API so that
      they can be changed without breaking compatibility.

    - exit_code added to scx_exit_info. This is used to indicate different
      exit conditions on non-error exits and will be used to handle e.g. CPU
      hotplugs.

    - The patch "sched_ext: Allow BPF schedulers to switch all eligible
      tasks into sched_ext" is folded in and the interface is changed so
      that partial switching is indicated with a new ops flag
      %SCX_OPS_SWITCH_PARTIAL. This makes scx_bpf_switch_all() unnecessasry
      and in turn SCX_KF_INIT. ops.init() is now called with
      SCX_KF_SLEEPABLE.

    - Code reorganized so that only the parts necessary to integrate with
      the rest of the kernel are in the header files.

    - Changes to reflect the BPF and other kernel changes including the
      addition of bpf_sched_ext_ops.cfi_stubs.

v5: - To accommodate 32bit configs, p->scx.ops_state is now atomic_long_t
      instead of atomic64_t and scx_dsp_buf_ent.qseq which uses
      load_acquire/store_release is now unsigned long instead of u64.

    - Fix the bug where bpf_scx_btf_struct_access() was allowing write
      access to arbitrary fields.

    - Distinguish kfuncs which can be called from any sched_ext ops and from
      anywhere. e.g. scx_bpf_pick_idle_cpu() can now be called only from
      sched_ext ops.

    - Rename "type" to "kind" in scx_exit_info to make it easier to use on
      languages in which "type" is a reserved keyword.

    - Since cff9b2332ab7 ("kernel/sched: Modify initial boot task idle
      setup"), PF_IDLE is not set on idle tasks which haven't been online
      yet which made scx_task_iter_next_filtered() include those idle tasks
      in iterations leading to oopses. Update scx_task_iter_next_filtered()
      to directly test p->sched_class against idle_sched_class instead of
      using is_idle_task() which tests PF_IDLE.

    - Other updates to match upstream changes such as adding const to
      set_cpumask() param and renaming check_preempt_curr() to
      wakeup_preempt().

v4: - SCHED_CHANGE_BLOCK replaced with the previous
      sched_deq_and_put_task()/sched_enq_and_set_tsak() pair. This is
      because upstream is adaopting a different generic cleanup mechanism.
      Once that lands, the code will be adapted accordingly.

    - task_on_scx() used to test whether a task should be switched into SCX,
      which is confusing. Renamed to task_should_scx(). task_on_scx() now
      tests whether a task is currently on SCX.

    - scx_has_idle_cpus is barely used anymore and replaced with direct
      check on the idle cpumask.

    - SCX_PICK_IDLE_CORE added and scx_pick_idle_cpu() improved to prefer
      fully idle cores.

    - ops.enable() now sees up-to-date p->scx.weight value.

    - ttwu_queue path is disabled for tasks on SCX to avoid confusing BPF
      schedulers expecting ->select_cpu() call.

    - Use cpu_smt_mask() instead of topology_sibling_cpumask() like the rest
      of the scheduler.

v3: - ops.set_weight() added to allow BPF schedulers to track weight changes
      without polling p->scx.weight.

    - move_task_to_local_dsq() was losing SCX-specific enq_flags when
      enqueueing the task on the target dsq because it goes through
      activate_task() which loses the upper 32bit of the flags. Carry the
      flags through rq->scx.extra_enq_flags.

    - scx_bpf_dispatch(), scx_bpf_pick_idle_cpu(), scx_bpf_task_running()
      and scx_bpf_task_cpu() now use the new KF_RCU instead of
      KF_TRUSTED_ARGS to make it easier for BPF schedulers to call them.

    - The kfunc helper access control mechanism implemented through
      sched_ext_entity.kf_mask is improved. Now SCX_CALL_OP*() is always
      used when invoking scx_ops operations.

v2: - balance_scx_on_up() is dropped. Instead, on UP, balance_scx() is
      called from put_prev_taks_scx() and pick_next_task_scx() as necessary.
      To determine whether balance_scx() should be called from
      put_prev_task_scx(), SCX_TASK_DEQD_FOR_SLEEP flag is added. See the
      comment in put_prev_task_scx() for details.

    - sched_deq_and_put_task() / sched_enq_and_set_task() sequences replaced
      with SCHED_CHANGE_BLOCK().

    - Unused all_dsqs list removed. This was a left-over from previous
      iterations.

    - p->scx.kf_mask is added to track and enforce which kfunc helpers are
      allowed. Also, init/exit sequences are updated to make some kfuncs
      always safe to call regardless of the current BPF scheduler state.
      Combined, this should make all the kfuncs safe.

    - BPF now supports sleepable struct_ops operations. Hacky workaround
      removed and operations and kfunc helpers are tagged appropriately.

    - BPF now supports bitmask / cpumask helpers. scx_bpf_get_idle_cpumask()
      and friends are added so that BPF schedulers can use the idle masks
      with the generic helpers. This replaces the hacky kfunc helpers added
      by a separate patch in V1.

    - CONFIG_SCHED_CLASS_EXT can no longer be enabled if SCHED_CORE is
      enabled. This restriction will be removed by a later patch which adds
      core-sched support.

    - Add MAINTAINERS entries and other misc changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Co-authored-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
Cc: Andrea Righi <andrea.righi@canonical.com>

Pull livepatching update from Petr Mladek:

 - Use more informative names for the livepatch transition states

* tag 'livepatching-for-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  livepatch: Rename KLP_* to KLP_TRANSITION_*

The original macros of KLP_* is about the state of the transition.
Rename macros of KLP_* to KLP_TRANSITION_* to fix the confusing
description of klp transition state.

Signed-off-by: Wardenjohn <zhangwarden@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20240507050111.38195-2-zhangwarden@gmail.com
Signed-off-by: Petr Mladek <pmladek@suse.com>