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Documentation: core-api/cpuhotplug: Rewrite the API section 

Dave stumbled over the incomplete and confusing documentation of the CPU
hotplug API.

Rewrite it, add the missing function documentations and correct the
existing ones.

Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210909123212.489059409@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-09-09 14:34:59 +02:00
parent 8c854303ce
commit c9871c800f
2 changed files with 569 additions and 100 deletions
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537
Documentation/core-api/cpu_hotplug.rst
View File

@ -2,12 +2,13 @@
CPU hotplug in the Kernel CPU hotplug in the Kernel
========================= =========================
:Date: December, 2016 :Date: September, 2021
:Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>, :Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Rusty Russell <rusty@rustcorp.com.au>, Rusty Russell <rusty@rustcorp.com.au>,
Srivatsa Vaddagiri <vatsa@in.ibm.com>, Srivatsa Vaddagiri <vatsa@in.ibm.com>,
Ashok Raj <ashok.raj@intel.com>, Ashok Raj <ashok.raj@intel.com>,
Joel Schopp <jschopp@austin.ibm.com> Joel Schopp <jschopp@austin.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>
Introduction Introduction
============ ============
@ -158,100 +159,480 @@ at state ``CPUHP_OFFLINE``. This includes:
* Once all services are migrated, kernel calls an arch specific routine * Once all services are migrated, kernel calls an arch specific routine
``__cpu_disable()`` to perform arch specific cleanup. ``__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 The CPU hotplug API
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> CPU hotplug state machine
-------------------------
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "X/Y:online", CPU hotplug uses a trivial state machine with a linear state space from
Y_online, Y_prepare_down); CPUHP_OFFLINE to CPUHP_ONLINE. Each state has a startup and a teardown
callback.
*X* is the subsystem and *Y* the particular driver. The *Y_online* callback When a CPU is onlined, the startup callbacks are invoked sequentially until
will be invoked during registration on all online CPUs. If an error the state CPUHP_ONLINE is reached. They can also be invoked when the
occurs during the online callback the *Y_prepare_down* callback will be callbacks of a state are set up or an instance is added to a multi-instance
invoked on all CPUs on which the online callback was previously invoked. state.
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 When a CPU is offlined the teardown callbacks are invoked in the reverse
dynamically allocated state (*CPUHP_AP_ONLINE_DYN*) use the returned state. order sequentially until the state CPUHP_OFFLINE is reached. They can also
During the removal of a hotplug state the teardown callback will be invoked. be invoked when the callbacks of a state are removed or an instance is
removed from a multi-instance state.
Multiple instances 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.
If a driver has multiple instances and each instance needs to perform the The state space is divided into three sections:
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, * The PREPARE section
Y_online, Y_prepare_down);
Y_hp_online = ret;
The ``cpuhp_setup_state_multi()`` behaves similar to ``cpuhp_setup_state()`` The PREPARE section covers the state space from CPUHP_OFFLINE to
except it prepares the callbacks for a multi state and does not invoke CPUHP_BRINGUP_CPU.
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); 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.
This function will add this instance to your previously allocated The callbacks are invoked on a control CPU as they can't obviously run on
*Y_hp_online* state and invoke the previously registered callback the hotplugged CPU which is either not yet started or has become
(*Y_online*) on all online CPUs. The *node* element is a ``struct dysfunctional already.
hlist_node`` member of your per-instance data structure.
On removal of the instance:: 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.
cpuhp_state_remove_instance(Y_hp_online, &d->node) 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.
should be invoked which will invoke the teardown callback on all online The teardown callbacks in this section are not allowed to fail.
CPUs.
Manual setup * The STARTING section
~~~~~~~~~~~~
Usually it is handy to invoke setup and teardown callbacks on registration or The STARTING section covers the state space between CPUHP_BRINGUP_CPU + 1
removal of a state because usually the operation needs to performed once a CPU and CPUHP_AP_ONLINE.
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 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 ordering of the events The callbacks in this section are not allowed to fail.
--------------------------
The hotplug states are defined in ``include/linux/cpuhotplug.h``: The callbacks are used for low level hardware initialization/shutdown and
for core subsystems.
* The states *CPUHP_OFFLINE* … *CPUHP_AP_OFFLINE* are invoked before the * The ONLINE section
CPU is up.
* The states *CPUHP_AP_OFFLINE* … *CPUHP_AP_ONLINE* are invoked The ONLINE section covers the state space between CPUHP_AP_ONLINE + 1 and
just the after the CPU has been brought up. The interrupts are off and CPUHP_ONLINE.
the scheduler is not yet active on this CPU. Starting with *CPUHP_AP_OFFLINE*
the callbacks are invoked on the target CPU. The startup callbacks in this section are invoked on the hotplugged CPU
* The states between *CPUHP_AP_ONLINE_DYN* and *CPUHP_AP_ONLINE_DYN_END* are during a CPU online operation. The teardown callbacks are invoked on the
reserved for the dynamic allocation. hotplugged CPU during a CPU offline operation.
* The states are invoked in the reverse order on CPU shutdown starting with
*CPUHP_ONLINE* and stopping at *CPUHP_OFFLINE*. Here the callbacks are The callbacks are invoked in the context of the per CPU hotplug thread,
invoked on the CPU that will be shutdown until *CPUHP_AP_OFFLINE*. 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);
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.
Testing of hotplug states Testing of hotplug states
========================= =========================

132
include/linux/cpuhotplug.h
View File

@ -22,8 +22,42 @@
* AP_ACTIVE AP_ACTIVE * AP_ACTIVE AP_ACTIVE
*/ */
/*
* CPU hotplug states. The state machine invokes the installed state
* startup callbacks sequentially from CPUHP_OFFLINE + 1 to CPUHP_ONLINE
* during a CPU online operation. During a CPU offline operation the
* installed teardown callbacks are invoked in the reverse order from
* CPU_ONLINE - 1 down to CPUHP_OFFLINE.
*
* The state space has three sections: PREPARE, STARTING and ONLINE.
*
* PREPARE: The callbacks are invoked on a control CPU before the
* hotplugged CPU is started up or after the hotplugged CPU has died.
*
* STARTING: The callbacks are invoked on the hotplugged CPU from the low level
* hotplug startup/teardown code with interrupts disabled.
*
* ONLINE: The callbacks are invoked on the hotplugged CPU from the per CPU
* hotplug thread with interrupts and preemption enabled.
*
* Adding explicit states to this enum is only necessary when:
*
* 1) The state is within the STARTING section
*
* 2) The state has ordering constraints vs. other states in the
* same section.
*
* If neither #1 nor #2 apply, please use the dynamic state space when
* setting up a state by using CPUHP_PREPARE_DYN or CPUHP_PREPARE_ONLINE
* for the @state argument of the setup function.
*
* See Documentation/core-api/cpu_hotplug.rst for further information and
* examples.
*/
enum cpuhp_state { enum cpuhp_state {
CPUHP_INVALID = -1, CPUHP_INVALID = -1,
/* PREPARE section invoked on a control CPU */
CPUHP_OFFLINE = 0, CPUHP_OFFLINE = 0,
CPUHP_CREATE_THREADS, CPUHP_CREATE_THREADS,
CPUHP_PERF_PREPARE, CPUHP_PERF_PREPARE,
@ -95,6 +129,11 @@ enum cpuhp_state {
CPUHP_BP_PREPARE_DYN, CPUHP_BP_PREPARE_DYN,
CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20, CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20,
CPUHP_BRINGUP_CPU, CPUHP_BRINGUP_CPU,
/*
* STARTING section invoked on the hotplugged CPU in low level
* bringup and teardown code.
*/
CPUHP_AP_IDLE_DEAD, CPUHP_AP_IDLE_DEAD,
CPUHP_AP_OFFLINE, CPUHP_AP_OFFLINE,
CPUHP_AP_SCHED_STARTING, CPUHP_AP_SCHED_STARTING,
@ -155,6 +194,8 @@ enum cpuhp_state {
CPUHP_AP_ARM_CACHE_B15_RAC_DYING, CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
CPUHP_AP_ONLINE, CPUHP_AP_ONLINE,
CPUHP_TEARDOWN_CPU, CPUHP_TEARDOWN_CPU,
/* Online section invoked on the hotplugged CPU from the hotplug thread */
CPUHP_AP_ONLINE_IDLE, CPUHP_AP_ONLINE_IDLE,
CPUHP_AP_SCHED_WAIT_EMPTY, CPUHP_AP_SCHED_WAIT_EMPTY,
CPUHP_AP_SMPBOOT_THREADS, CPUHP_AP_SMPBOOT_THREADS,
@ -216,14 +257,15 @@ int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state, const char *name,
int (*teardown)(unsigned int cpu), int (*teardown)(unsigned int cpu),
bool multi_instance); bool multi_instance);
/** /**
* cpuhp_setup_state - Setup hotplug state callbacks with calling the callbacks * cpuhp_setup_state - Setup hotplug state callbacks with calling the @startup
* callback
* @state: The state for which the calls are installed * @state: The state for which the calls are installed
* @name: Name of the callback (will be used in debug output) * @name: Name of the callback (will be used in debug output)
* @startup: startup callback function * @startup: startup callback function or NULL if not required
* @teardown: teardown callback function * @teardown: teardown callback function or NULL if not required
* *
* Installs the callback functions and invokes the startup callback on * Installs the callback functions and invokes the @startup callback on
* the present cpus which have already reached the @state. * the online cpus which have already reached the @state.
*/ */
static inline int cpuhp_setup_state(enum cpuhp_state state, static inline int cpuhp_setup_state(enum cpuhp_state state,
const char *name, const char *name,
@ -233,6 +275,18 @@ static inline int cpuhp_setup_state(enum cpuhp_state state,
return __cpuhp_setup_state(state, name, true, startup, teardown, false); return __cpuhp_setup_state(state, name, true, startup, teardown, false);
} }
/**
* cpuhp_setup_state_cpuslocked - Setup hotplug state callbacks with calling
* @startup callback from a cpus_read_lock()
* held region
* @state: The state for which the calls are installed
* @name: Name of the callback (will be used in debug output)
* @startup: startup callback function or NULL if not required
* @teardown: teardown callback function or NULL if not required
*
* Same as cpuhp_setup_state() except that it must be invoked from within a
* cpus_read_lock() held region.
*/
static inline int cpuhp_setup_state_cpuslocked(enum cpuhp_state state, static inline int cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
const char *name, const char *name,
int (*startup)(unsigned int cpu), int (*startup)(unsigned int cpu),
@ -244,14 +298,14 @@ static inline int cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
/** /**
* cpuhp_setup_state_nocalls - Setup hotplug state callbacks without calling the * cpuhp_setup_state_nocalls - Setup hotplug state callbacks without calling the
* callbacks * @startup callback
* @state: The state for which the calls are installed * @state: The state for which the calls are installed
* @name: Name of the callback. * @name: Name of the callback.
* @startup: startup callback function * @startup: startup callback function or NULL if not required
* @teardown: teardown callback function * @teardown: teardown callback function or NULL if not required
* *
* Same as @cpuhp_setup_state except that no calls are executed are invoked * Same as cpuhp_setup_state() except that the @startup callback is not
* during installation of this callback. NOP if SMP=n or HOTPLUG_CPU=n. * invoked during installation. NOP if SMP=n or HOTPLUG_CPU=n.
*/ */
static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state, static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
const char *name, const char *name,
@ -262,6 +316,19 @@ static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
false); false);
} }
/**
* cpuhp_setup_state_nocalls_cpuslocked - Setup hotplug state callbacks without
* invoking the @startup callback from
* a cpus_read_lock() held region
* callbacks
* @state: The state for which the calls are installed
* @name: Name of the callback.
* @startup: startup callback function or NULL if not required
* @teardown: teardown callback function or NULL if not required
*
* Same as cpuhp_setup_state_nocalls() except that it must be invoked from
* within a cpus_read_lock() held region.
*/
static inline int cpuhp_setup_state_nocalls_cpuslocked(enum cpuhp_state state, static inline int cpuhp_setup_state_nocalls_cpuslocked(enum cpuhp_state state,
const char *name, const char *name,
int (*startup)(unsigned int cpu), int (*startup)(unsigned int cpu),
@ -275,13 +342,13 @@ static inline int cpuhp_setup_state_nocalls_cpuslocked(enum cpuhp_state state,
* cpuhp_setup_state_multi - Add callbacks for multi state * cpuhp_setup_state_multi - Add callbacks for multi state
* @state: The state for which the calls are installed * @state: The state for which the calls are installed
* @name: Name of the callback. * @name: Name of the callback.
* @startup: startup callback function * @startup: startup callback function or NULL if not required
* @teardown: teardown callback function * @teardown: teardown callback function or NULL if not required
* *
* Sets the internal multi_instance flag and prepares a state to work as a multi * Sets the internal multi_instance flag and prepares a state to work as a multi
* instance callback. No callbacks are invoked at this point. The callbacks are * instance callback. No callbacks are invoked at this point. The callbacks are
* invoked once an instance for this state are registered via * invoked once an instance for this state are registered via
* @cpuhp_state_add_instance or @cpuhp_state_add_instance_nocalls. * cpuhp_state_add_instance() or cpuhp_state_add_instance_nocalls()
*/ */
static inline int cpuhp_setup_state_multi(enum cpuhp_state state, static inline int cpuhp_setup_state_multi(enum cpuhp_state state,
const char *name, const char *name,
@ -306,9 +373,10 @@ int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
* @state: The state for which the instance is installed * @state: The state for which the instance is installed
* @node: The node for this individual state. * @node: The node for this individual state.
* *
* Installs the instance for the @state and invokes the startup callback on * Installs the instance for the @state and invokes the registered startup
* the present cpus which have already reached the @state. The @state must have * callback on the online cpus which have already reached the @state. The
* been earlier marked as multi-instance by @cpuhp_setup_state_multi. * @state must have been earlier marked as multi-instance by
* cpuhp_setup_state_multi().
*/ */
static inline int cpuhp_state_add_instance(enum cpuhp_state state, static inline int cpuhp_state_add_instance(enum cpuhp_state state,
struct hlist_node *node) struct hlist_node *node)
@ -322,8 +390,9 @@ static inline int cpuhp_state_add_instance(enum cpuhp_state state,
* @state: The state for which the instance is installed * @state: The state for which the instance is installed
* @node: The node for this individual state. * @node: The node for this individual state.
* *
* Installs the instance for the @state The @state must have been earlier * Installs the instance for the @state. The @state must have been earlier
* marked as multi-instance by @cpuhp_setup_state_multi. * marked as multi-instance by cpuhp_setup_state_multi. NOP if SMP=n or
* HOTPLUG_CPU=n.
*/ */
static inline int cpuhp_state_add_instance_nocalls(enum cpuhp_state state, static inline int cpuhp_state_add_instance_nocalls(enum cpuhp_state state,
struct hlist_node *node) struct hlist_node *node)
@ -331,6 +400,17 @@ static inline int cpuhp_state_add_instance_nocalls(enum cpuhp_state state,
return __cpuhp_state_add_instance(state, node, false); return __cpuhp_state_add_instance(state, node, false);
} }
/**
* cpuhp_state_add_instance_nocalls_cpuslocked - Add an instance for a state
* without invoking the startup
* callback from a cpus_read_lock()
* held region.
* @state: The state for which the instance is installed
* @node: The node for this individual state.
*
* Same as cpuhp_state_add_instance_nocalls() except that it must be
* invoked from within a cpus_read_lock() held region.
*/
static inline int static inline int
cpuhp_state_add_instance_nocalls_cpuslocked(enum cpuhp_state state, cpuhp_state_add_instance_nocalls_cpuslocked(enum cpuhp_state state,
struct hlist_node *node) struct hlist_node *node)
@ -346,7 +426,7 @@ void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke);
* @state: The state for which the calls are removed * @state: The state for which the calls are removed
* *
* Removes the callback functions and invokes the teardown callback on * Removes the callback functions and invokes the teardown callback on
* the present cpus which have already reached the @state. * the online cpus which have already reached the @state.
*/ */
static inline void cpuhp_remove_state(enum cpuhp_state state) static inline void cpuhp_remove_state(enum cpuhp_state state)
{ {
@ -355,7 +435,7 @@ static inline void cpuhp_remove_state(enum cpuhp_state state)
/** /**
* cpuhp_remove_state_nocalls - Remove hotplug state callbacks without invoking * cpuhp_remove_state_nocalls - Remove hotplug state callbacks without invoking
* teardown * the teardown callback
* @state: The state for which the calls are removed * @state: The state for which the calls are removed
*/ */
static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state) static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state)
@ -363,6 +443,14 @@ static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state)
__cpuhp_remove_state(state, false); __cpuhp_remove_state(state, false);
} }
/**
* cpuhp_remove_state_nocalls_cpuslocked - Remove hotplug state callbacks without invoking
* teardown from a cpus_read_lock() held region.
* @state: The state for which the calls are removed
*
* Same as cpuhp_remove_state nocalls() except that it must be invoked
* from within a cpus_read_lock() held region.
*/
static inline void cpuhp_remove_state_nocalls_cpuslocked(enum cpuhp_state state) static inline void cpuhp_remove_state_nocalls_cpuslocked(enum cpuhp_state state)
{ {
__cpuhp_remove_state_cpuslocked(state, false); __cpuhp_remove_state_cpuslocked(state, false);
@ -390,8 +478,8 @@ int __cpuhp_state_remove_instance(enum cpuhp_state state,
* @state: The state from which the instance is removed * @state: The state from which the instance is removed
* @node: The node for this individual state. * @node: The node for this individual state.
* *
* Removes the instance and invokes the teardown callback on the present cpus * Removes the instance and invokes the teardown callback on the online cpus
* which have already reached the @state. * which have already reached @state.
*/ */
static inline int cpuhp_state_remove_instance(enum cpuhp_state state, static inline int cpuhp_state_remove_instance(enum cpuhp_state state,
struct hlist_node *node) struct hlist_node *node)