Merge tag 'smp-urgent-2021-09-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug updates from Thomas Gleixner:
 "Updates for the SMP and CPU hotplug:

   - Remove DEFINE_SMP_CALL_CACHE_FUNCTION() which is a left over of the
     original hotplug code and now causing trouble with the ARM64 cache
     topology setup due to the pointless SMP function call.

     It's not longer required as the hotplug callbacks are guaranteed to
     be invoked on the upcoming CPU.

   - Remove the deprecated and now unused CPU hotplug functions

   - Rewrite the CPU hotplug API documentation"

* tag 'smp-urgent-2021-09-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation: core-api/cpuhotplug: Rewrite the API section
  cpu/hotplug: Remove deprecated CPU-hotplug functions.
  thermal: Replace deprecated CPU-hotplug functions.
  drivers: base: cacheinfo: Get rid of DEFINE_SMP_CALL_CACHE_FUNCTION()

1 files changed, 480 insertions, 99 deletions

diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
index b66e3cae1472..c6f4ba2fb32d 100644
--- a/Documentation/core-api/cpu_hotplug.rst
+++ b/Documentation/core-api/cpu_hotplug.rst
@@ -2,12 +2,13 @@
 CPU hotplug in the Kernel
 =========================
 
-:Date: December, 2016
+:Date: September, 2021
 :Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
-          Rusty Russell <rusty@rustcorp.com.au>,
-          Srivatsa Vaddagiri <vatsa@in.ibm.com>,
-          Ashok Raj <ashok.raj@intel.com>,
-          Joel Schopp <jschopp@austin.ibm.com>
+         Rusty Russell <rusty@rustcorp.com.au>,
+         Srivatsa Vaddagiri <vatsa@in.ibm.com>,
+         Ashok Raj <ashok.raj@intel.com>,
+         Joel Schopp <jschopp@austin.ibm.com>,
+	 Thomas Gleixner <tglx@linutronix.de>
 
 Introduction
 ============
@@ -158,100 +159,480 @@ at state ``CPUHP_OFFLINE``. This includes:
 * Once all services are migrated, kernel calls an arch specific routine
   ``__cpu_disable()`` to perform arch specific cleanup.
 
-Using the hotplug API
----------------------
-
-It is possible to receive notifications once a CPU is offline or onlined. This
-might be important to certain drivers which need to perform some kind of setup
-or clean up functions based on the number of available CPUs::
-
-  #include <linux/cpuhotplug.h>
-
-  ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "X/Y:online",
-                          Y_online, Y_prepare_down);
-
-*X* is the subsystem and *Y* the particular driver. The *Y_online* callback
-will be invoked during registration on all online CPUs. If an error
-occurs during the online callback the *Y_prepare_down* callback will be
-invoked on all CPUs on which the online callback was previously invoked.
-After registration completed, the *Y_online* callback will be invoked
-once a CPU is brought online and *Y_prepare_down* will be invoked when a
-CPU is shutdown. All resources which were previously allocated in
-*Y_online* should be released in *Y_prepare_down*.
-The return value *ret* is negative if an error occurred during the
-registration process. Otherwise a positive value is returned which
-contains the allocated hotplug for dynamically allocated states
-(*CPUHP_AP_ONLINE_DYN*). It will return zero for predefined states.
-
-The callback can be remove by invoking ``cpuhp_remove_state()``. In case of a
-dynamically allocated state (*CPUHP_AP_ONLINE_DYN*) use the returned state.
-During the removal of a hotplug state the teardown callback will be invoked.
-
-Multiple instances
-~~~~~~~~~~~~~~~~~~
-
-If a driver has multiple instances and each instance needs to perform the
-callback independently then it is likely that a ''multi-state'' should be used.
-First a multi-state state needs to be registered::
-
-  ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "X/Y:online,
-                                Y_online, Y_prepare_down);
-  Y_hp_online = ret;
-
-The ``cpuhp_setup_state_multi()`` behaves similar to ``cpuhp_setup_state()``
-except it prepares the callbacks for a multi state and does not invoke
-the callbacks. This is a one time setup.
-Once a new instance is allocated, you need to register this new instance::
-
-  ret = cpuhp_state_add_instance(Y_hp_online, &d->node);
-
-This function will add this instance to your previously allocated
-*Y_hp_online* state and invoke the previously registered callback
-(*Y_online*) on all online CPUs. The *node* element is a ``struct
-hlist_node`` member of your per-instance data structure.
-
-On removal of the instance::
-
-  cpuhp_state_remove_instance(Y_hp_online, &d->node)
-
-should be invoked which will invoke the teardown callback on all online
-CPUs.
-
-Manual setup
-~~~~~~~~~~~~
-
-Usually it is handy to invoke setup and teardown callbacks on registration or
-removal of a state because usually the operation needs to performed once a CPU
-goes online (offline) and during initial setup (shutdown) of the driver. However
-each registration and removal function is also available with a ``_nocalls``
-suffix which does not invoke the provided callbacks if the invocation of the
-callbacks is not desired. During the manual setup (or teardown) the functions
-``cpus_read_lock()`` and ``cpus_read_unlock()`` should be used to inhibit CPU
-hotplug operations.
-
-
-The ordering of the events
---------------------------
-
-The hotplug states are defined in ``include/linux/cpuhotplug.h``:
-
-* The states *CPUHP_OFFLINE* … *CPUHP_AP_OFFLINE* are invoked before the
-  CPU is up.
-* The states *CPUHP_AP_OFFLINE* … *CPUHP_AP_ONLINE* are invoked
-  just the after the CPU has been brought up. The interrupts are off and
-  the scheduler is not yet active on this CPU. Starting with *CPUHP_AP_OFFLINE*
-  the callbacks are invoked on the target CPU.
-* The states between *CPUHP_AP_ONLINE_DYN* and *CPUHP_AP_ONLINE_DYN_END* are
-  reserved for the dynamic allocation.
-* The states are invoked in the reverse order on CPU shutdown starting with
-  *CPUHP_ONLINE* and stopping at *CPUHP_OFFLINE*. Here the callbacks are
-  invoked on the CPU that will be shutdown until *CPUHP_AP_OFFLINE*.
-
-A dynamically allocated state via *CPUHP_AP_ONLINE_DYN* is often enough.
-However if an earlier invocation during the bring up or shutdown is required
-then an explicit state should be acquired. An explicit state might also be
-required if the hotplug event requires specific ordering in respect to
-another hotplug event.
+
+The CPU hotplug API
+===================
+
+CPU hotplug state machine
+-------------------------
+
+CPU hotplug uses a trivial state machine with a linear state space from
+CPUHP_OFFLINE to CPUHP_ONLINE. Each state has a startup and a teardown
+callback.
+
+When a CPU is onlined, the startup callbacks are invoked sequentially until
+the state CPUHP_ONLINE is reached. They can also be invoked when the
+callbacks of a state are set up or an instance is added to a multi-instance
+state.
+
+When a CPU is offlined the teardown callbacks are invoked in the reverse
+order sequentially until the state CPUHP_OFFLINE is reached. They can also
+be invoked when the callbacks of a state are removed or an instance is
+removed from a multi-instance state.
+
+If a usage site requires only a callback in one direction of the hotplug
+operations (CPU online or CPU offline) then the other not-required callback
+can be set to NULL when the state is set up.
+
+The state space is divided into three sections:
+
+* The PREPARE section
+
+  The PREPARE section covers the state space from CPUHP_OFFLINE to
+  CPUHP_BRINGUP_CPU.
+
+  The startup callbacks in this section are invoked before the CPU is
+  started during a CPU online operation. The teardown callbacks are invoked
+  after the CPU has become dysfunctional during a CPU offline operation.
+
+  The callbacks are invoked on a control CPU as they can't obviously run on
+  the hotplugged CPU which is either not yet started or has become
+  dysfunctional already.
+
+  The startup callbacks are used to setup resources which are required to
+  bring a CPU successfully online. The teardown callbacks are used to free
+  resources or to move pending work to an online CPU after the hotplugged
+  CPU became dysfunctional.
+
+  The startup callbacks are allowed to fail. If a callback fails, the CPU
+  online operation is aborted and the CPU is brought down to the previous
+  state (usually CPUHP_OFFLINE) again.
+
+  The teardown callbacks in this section are not allowed to fail.
+
+* The STARTING section
+
+  The STARTING section covers the state space between CPUHP_BRINGUP_CPU + 1
+  and CPUHP_AP_ONLINE.
+
+  The startup callbacks in this section are invoked on the hotplugged CPU
+  with interrupts disabled during a CPU online operation in the early CPU
+  setup code. The teardown callbacks are invoked with interrupts disabled
+  on the hotplugged CPU during a CPU offline operation shortly before the
+  CPU is completely shut down.
+
+  The callbacks in this section are not allowed to fail.
+
+  The callbacks are used for low level hardware initialization/shutdown and
+  for core subsystems.
+
+* The ONLINE section
+
+  The ONLINE section covers the state space between CPUHP_AP_ONLINE + 1 and
+  CPUHP_ONLINE.
+
+  The startup callbacks in this section are invoked on the hotplugged CPU
+  during a CPU online operation. The teardown callbacks are invoked on the
+  hotplugged CPU during a CPU offline operation.
+
+  The callbacks are invoked in the context of the per CPU hotplug thread,
+  which is pinned on the hotplugged CPU. The callbacks are invoked with
+  interrupts and preemption enabled.
+
+  The callbacks are allowed to fail. When a callback fails the hotplug
+  operation is aborted and the CPU is brought back to the previous state.
+
+CPU online/offline operations
+-----------------------------
+
+A successful online operation looks like this::
+
+  [CPUHP_OFFLINE]
+  [CPUHP_OFFLINE + 1]->startup()       -> success
+  [CPUHP_OFFLINE + 2]->startup()       -> success
+  [CPUHP_OFFLINE + 3]                  -> skipped because startup == NULL
+  ...
+  [CPUHP_BRINGUP_CPU]->startup()       -> success
+  === End of PREPARE section
+  [CPUHP_BRINGUP_CPU + 1]->startup()   -> success
+  ...
+  [CPUHP_AP_ONLINE]->startup()         -> success
+  === End of STARTUP section
+  [CPUHP_AP_ONLINE + 1]->startup()     -> success
+  ...
+  [CPUHP_ONLINE - 1]->startup()        -> success
+  [CPUHP_ONLINE]
+
+A successful offline operation looks like this::
+
+  [CPUHP_ONLINE]
+  [CPUHP_ONLINE - 1]->teardown()       -> success
+  ...
+  [CPUHP_AP_ONLINE + 1]->teardown()    -> success
+  === Start of STARTUP section
+  [CPUHP_AP_ONLINE]->teardown()        -> success
+  ...
+  [CPUHP_BRINGUP_ONLINE - 1]->teardown()
+  ...
+  === Start of PREPARE section
+  [CPUHP_BRINGUP_CPU]->teardown()
+  [CPUHP_OFFLINE + 3]->teardown()
+  [CPUHP_OFFLINE + 2]                  -> skipped because teardown == NULL
+  [CPUHP_OFFLINE + 1]->teardown()
+  [CPUHP_OFFLINE]
+
+A failed online operation looks like this::
+
+  [CPUHP_OFFLINE]
+  [CPUHP_OFFLINE + 1]->startup()       -> success
+  [CPUHP_OFFLINE + 2]->startup()       -> success
+  [CPUHP_OFFLINE + 3]                  -> skipped because startup == NULL
+  ...
+  [CPUHP_BRINGUP_CPU]->startup()       -> success
+  === End of PREPARE section
+  [CPUHP_BRINGUP_CPU + 1]->startup()   -> success
+  ...
+  [CPUHP_AP_ONLINE]->startup()         -> success
+  === End of STARTUP section
+  [CPUHP_AP_ONLINE + 1]->startup()     -> success
+  ---
+  [CPUHP_AP_ONLINE + N]->startup()     -> fail
+  [CPUHP_AP_ONLINE + (N - 1)]->teardown()
+  ...
+  [CPUHP_AP_ONLINE + 1]->teardown()
+  === Start of STARTUP section
+  [CPUHP_AP_ONLINE]->teardown()
+  ...
+  [CPUHP_BRINGUP_ONLINE - 1]->teardown()
+  ...
+  === Start of PREPARE section
+  [CPUHP_BRINGUP_CPU]->teardown()
+  [CPUHP_OFFLINE + 3]->teardown()
+  [CPUHP_OFFLINE + 2]                  -> skipped because teardown == NULL
+  [CPUHP_OFFLINE + 1]->teardown()
+  [CPUHP_OFFLINE]
+
+A failed offline operation looks like this::
+
+  [CPUHP_ONLINE]
+  [CPUHP_ONLINE - 1]->teardown()       -> success
+  ...
+  [CPUHP_ONLINE - N]->teardown()       -> fail
+  [CPUHP_ONLINE - (N - 1)]->startup()
+  ...
+  [CPUHP_ONLINE - 1]->startup()
+  [CPUHP_ONLINE]
+
+Recursive failures cannot be handled sensibly. Look at the following
+example of a recursive fail due to a failed offline operation: ::
+
+  [CPUHP_ONLINE]
+  [CPUHP_ONLINE - 1]->teardown()       -> success
+  ...
+  [CPUHP_ONLINE - N]->teardown()       -> fail
+  [CPUHP_ONLINE - (N - 1)]->startup()  -> success
+  [CPUHP_ONLINE - (N - 2)]->startup()  -> fail
+
+The CPU hotplug state machine stops right here and does not try to go back
+down again because that would likely result in an endless loop::
+
+  [CPUHP_ONLINE - (N - 1)]->teardown() -> success
+  [CPUHP_ONLINE - N]->teardown()       -> fail
+  [CPUHP_ONLINE - (N - 1)]->startup()  -> success
+  [CPUHP_ONLINE - (N - 2)]->startup()  -> fail
+  [CPUHP_ONLINE - (N - 1)]->teardown() -> success
+  [CPUHP_ONLINE - N]->teardown()       -> fail
+
+Lather, rinse and repeat. In this case the CPU left in state::
+
+  [CPUHP_ONLINE - (N - 1)]
+
+which at least lets the system make progress and gives the user a chance to
+debug or even resolve the situation.
+
+Allocating a state
+------------------
+
+There are two ways to allocate a CPU hotplug state:
+
+* Static allocation
+
+  Static allocation has to be used when the subsystem or driver has
+  ordering requirements versus other CPU hotplug states. E.g. the PERF core
+  startup callback has to be invoked before the PERF driver startup
+  callbacks during a CPU online operation. During a CPU offline operation
+  the driver teardown callbacks have to be invoked before the core teardown
+  callback. The statically allocated states are described by constants in
+  the cpuhp_state enum which can be found in include/linux/cpuhotplug.h.
+
+  Insert the state into the enum at the proper place so the ordering
+  requirements are fulfilled. The state constant has to be used for state
+  setup and removal.
+
+  Static allocation is also required when the state callbacks are not set
+  up at runtime and are part of the initializer of the CPU hotplug state
+  array in kernel/cpu.c.
+
+* Dynamic allocation
+
+  When there are no ordering requirements for the state callbacks then
+  dynamic allocation is the preferred method. The state number is allocated
+  by the setup function and returned to the caller on success.
+
+  Only the PREPARE and ONLINE sections provide a dynamic allocation
+  range. The STARTING section does not as most of the callbacks in that
+  section have explicit ordering requirements.
+
+Setup of a CPU hotplug state
+----------------------------
+
+The core code provides the following functions to setup a state:
+
+* cpuhp_setup_state(state, name, startup, teardown)
+* cpuhp_setup_state_nocalls(state, name, startup, teardown)
+* cpuhp_setup_state_cpuslocked(state, name, startup, teardown)
+* cpuhp_setup_state_nocalls_cpuslocked(state, name, startup, teardown)
+
+For cases where a driver or a subsystem has multiple instances and the same
+CPU hotplug state callbacks need to be invoked for each instance, the CPU
+hotplug core provides multi-instance support. The advantage over driver
+specific instance lists is that the instance related functions are fully
+serialized against CPU hotplug operations and provide the automatic
+invocations of the state callbacks on add and removal. To set up such a
+multi-instance state the following function is available:
+
+* cpuhp_setup_state_multi(state, name, startup, teardown)
+
+The @state argument is either a statically allocated state or one of the
+constants for dynamically allocated states - CPUHP_PREPARE_DYN,
+CPUHP_ONLINE_DYN - depending on the state section (PREPARE, ONLINE) for
+which a dynamic state should be allocated.
+
+The @name argument is used for sysfs output and for instrumentation. The
+naming convention is "subsys:mode" or "subsys/driver:mode",
+e.g. "perf:mode" or "perf/x86:mode". The common mode names are:
+
+======== =======================================================
+prepare  For states in the PREPARE section
+
+dead     For states in the PREPARE section which do not provide
+         a startup callback
+
+starting For states in the STARTING section
+
+dying    For states in the STARTING section which do not provide
+         a startup callback
+
+online   For states in the ONLINE section
+
+offline  For states in the ONLINE section which do not provide
+         a startup callback
+======== =======================================================
+
+As the @name argument is only used for sysfs and instrumentation other mode
+descriptors can be used as well if they describe the nature of the state
+better than the common ones.
+
+Examples for @name arguments: "perf/online", "perf/x86:prepare",
+"RCU/tree:dying", "sched/waitempty"
+
+The @startup argument is a function pointer to the callback which should be
+invoked during a CPU online operation. If the usage site does not require a
+startup callback set the pointer to NULL.
+
+The @teardown argument is a function pointer to the callback which should
+be invoked during a CPU offline operation. If the usage site does not
+require a teardown callback set the pointer to NULL.
+
+The functions differ in the way how the installed callbacks are treated:
+
+  * cpuhp_setup_state_nocalls(), cpuhp_setup_state_nocalls_cpuslocked()
+    and cpuhp_setup_state_multi() only install the callbacks
+
+  * cpuhp_setup_state() and cpuhp_setup_state_cpuslocked() install the
+    callbacks and invoke the @startup callback (if not NULL) for all online
+    CPUs which have currently a state greater than the newly installed
+    state. Depending on the state section the callback is either invoked on
+    the current CPU (PREPARE section) or on each online CPU (ONLINE
+    section) in the context of the CPU's hotplug thread.
+
+    If a callback fails for CPU N then the teardown callback for CPU
+    0 .. N-1 is invoked to rollback the operation. The state setup fails,
+    the callbacks for the state are not installed and in case of dynamic
+    allocation the allocated state is freed.
+
+The state setup and the callback invocations are serialized against CPU
+hotplug operations. If the setup function has to be called from a CPU
+hotplug read locked region, then the _cpuslocked() variants have to be
+used. These functions cannot be used from within CPU hotplug callbacks.
+
+The function return values:
+  ======== ===================================================================
+  0        Statically allocated state was successfully set up
+
+  >0       Dynamically allocated state was successfully set up.
+
+           The returned number is the state number which was allocated. If
+           the state callbacks have to be removed later, e.g. module
+           removal, then this number has to be saved by the caller and used
+           as @state argument for the state remove function. For
+           multi-instance states the dynamically allocated state number is
+           also required as @state argument for the instance add/remove
+           operations.
+
+  <0	   Operation failed
+  ======== ===================================================================
+
+Removal of a CPU hotplug state
+------------------------------
+
+To remove a previously set up state, the following functions are provided:
+
+* cpuhp_remove_state(state)
+* cpuhp_remove_state_nocalls(state)
+* cpuhp_remove_state_nocalls_cpuslocked(state)
+* cpuhp_remove_multi_state(state)
+
+The @state argument is either a statically allocated state or the state
+number which was allocated in the dynamic range by cpuhp_setup_state*(). If
+the state is in the dynamic range, then the state number is freed and
+available for dynamic allocation again.
+
+The functions differ in the way how the installed callbacks are treated:
+
+  * cpuhp_remove_state_nocalls(), cpuhp_remove_state_nocalls_cpuslocked()
+    and cpuhp_remove_multi_state() only remove the callbacks.
+
+  * cpuhp_remove_state() removes the callbacks and invokes the teardown
+    callback (if not NULL) for all online CPUs which have currently a state
+    greater than the removed state. Depending on the state section the
+    callback is either invoked on the current CPU (PREPARE section) or on
+    each online CPU (ONLINE section) in the context of the CPU's hotplug
+    thread.
+
+    In order to complete the removal, the teardown callback should not fail.
+
+The state removal and the callback invocations are serialized against CPU
+hotplug operations. If the remove function has to be called from a CPU
+hotplug read locked region, then the _cpuslocked() variants have to be
+used. These functions cannot be used from within CPU hotplug callbacks.
+
+If a multi-instance state is removed then the caller has to remove all
+instances first.
+
+Multi-Instance state instance management
+----------------------------------------
+
+Once the multi-instance state is set up, instances can be added to the
+state:
+
+  * cpuhp_state_add_instance(state, node)
+  * cpuhp_state_add_instance_nocalls(state, node)
+
+The @state argument is either a statically allocated state or the state
+number which was allocated in the dynamic range by cpuhp_setup_state_multi().
+
+The @node argument is a pointer to an hlist_node which is embedded in the
+instance's data structure. The pointer is handed to the multi-instance
+state callbacks and can be used by the callback to retrieve the instance
+via container_of().
+
+The functions differ in the way how the installed callbacks are treated:
+
+  * cpuhp_state_add_instance_nocalls() and only adds the instance to the
+    multi-instance state's node list.
+
+  * cpuhp_state_add_instance() adds the instance and invokes the startup
+    callback (if not NULL) associated with @state for all online CPUs which
+    have currently a state greater than @state. The callback is only
+    invoked for the to be added instance. Depending on the state section
+    the callback is either invoked on the current CPU (PREPARE section) or
+    on each online CPU (ONLINE section) in the context of the CPU's hotplug
+    thread.
+
+    If a callback fails for CPU N then the teardown callback for CPU
+    0 .. N-1 is invoked to rollback the operation, the function fails and
+    the instance is not added to the node list of the multi-instance state.
+
+To remove an instance from the state's node list these functions are
+available:
+
+  * cpuhp_state_remove_instance(state, node)
+  * cpuhp_state_remove_instance_nocalls(state, node)
+
+The arguments are the same as for the the cpuhp_state_add_instance*()
+variants above.
+
+The functions differ in the way how the installed callbacks are treated:
+
+  * cpuhp_state_remove_instance_nocalls() only removes the instance from the
+    state's node list.
+
+  * cpuhp_state_remove_instance() removes the instance and invokes the
+    teardown callback (if not NULL) associated with @state for all online
+    CPUs which have currently a state greater than @state.  The callback is
+    only invoked for the to be removed instance.  Depending on the state
+    section the callback is either invoked on the current CPU (PREPARE
+    section) or on each online CPU (ONLINE section) in the context of the
+    CPU's hotplug thread.
+
+    In order to complete the removal, the teardown callback should not fail.
+
+The node list add/remove operations and the callback invocations are
+serialized against CPU hotplug operations. These functions cannot be used
+from within CPU hotplug callbacks and CPU hotplug read locked regions.
+
+Examples
+--------
+
+Setup and teardown a statically allocated state in the STARTING section for
+notifications on online and offline operations::
+
+   ret = cpuhp_setup_state(CPUHP_SUBSYS_STARTING, "subsys:starting", subsys_cpu_starting, subsys_cpu_dying);
+   if (ret < 0)
+        return ret;
+   ....
+   cpuhp_remove_state(CPUHP_SUBSYS_STARTING);
+
+Setup and teardown a dynamically allocated state in the ONLINE section
+for notifications on offline operations::
+
+   state = cpuhp_setup_state(CPUHP_ONLINE_DYN, "subsys:offline", NULL, subsys_cpu_offline);
+   if (state < 0)
+       return state;
+   ....
+   cpuhp_remove_state(state);
+
+Setup and teardown a dynamically allocated state in the ONLINE section
+for notifications on online operations without invoking the callbacks::
+
+   state = cpuhp_setup_state_nocalls(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, NULL);
+   if (state < 0)
+       return state;
+   ....
+   cpuhp_remove_state_nocalls(state);
+
+Setup, use and teardown a dynamically allocated multi-instance state in the
+ONLINE section for notifications on online and offline operation::
+
+   state = cpuhp_setup_state_multi(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, subsys_cpu_offline);
+   if (state < 0)
+       return state;
+   ....
+   ret = cpuhp_state_add_instance(state, &inst1->node);
+   if (ret)
+        return ret;
+   ....
+   ret = cpuhp_state_add_instance(state, &inst2->node);
+   if (ret)
+        return ret;
+   ....
+   cpuhp_remove_instance(state, &inst1->node);
+   ....
+   cpuhp_remove_instance(state, &inst2->node);
+   ....
+   remove_multi_state(state);
+
 
 Testing of hotplug states
 =========================