cpuhotplug.h | Explore in Territory

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __CPUHOTPLUG_H
#define __CPUHOTPLUG_H

#include <linux/types.h>

/*
 * CPU-up			CPU-down
 *
 * BP		AP		BP		AP
 *
 * OFFLINE			OFFLINE
 *   |				  ^
 *   v				  |
 * BRINGUP_CPU->AP_OFFLINE	BRINGUP_CPU  <- AP_IDLE_DEAD (idle thread/play_dead)
 *		  |				AP_OFFLINE
 *		  v (IRQ-off)	  ,---------------^
 *		AP_ONLNE	  | (stop_machine)
 *		  |		TEARDOWN_CPU <-	AP_ONLINE_IDLE
 *		  |				  ^
 *		  v				  |
 *              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
 * CPUHP_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_BP_PREPARE_DYN or CPUHP_AP_ONLINE_DYN
 * for the @state argument of the setup function.
 *
 * See Documentation/core-api/cpu_hotplug.rst for further information and
 * examples.
 */
enum cpuhp_state { … };

int __cpuhp_setup_state(enum cpuhp_state state,	const char *name, bool invoke,
			int (*startup)(unsigned int cpu),
			int (*teardown)(unsigned int cpu), bool multi_instance);

int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state, const char *name,
				   bool invoke,
				   int (*startup)(unsigned int cpu),
				   int (*teardown)(unsigned int cpu),
				   bool multi_instance);
/**
 * cpuhp_setup_state - Setup hotplug state callbacks with calling the @startup
 *                     callback
 * @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
 *
 * Installs the callback functions and invokes the @startup callback on
 * the online cpus which have already reached the @state.
 */
static inline int cpuhp_setup_state(enum cpuhp_state state,
				    const char *name,
				    int (*startup)(unsigned int cpu),
				    int (*teardown)(unsigned int cpu))
{ … }

/**
 * 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,
					       const char *name,
					       int (*startup)(unsigned int cpu),
					       int (*teardown)(unsigned int cpu))
{ … }

/**
 * cpuhp_setup_state_nocalls - Setup hotplug state callbacks without calling the
 *			       @startup callback
 * @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() except that the @startup callback is not
 * invoked during installation. NOP if SMP=n or HOTPLUG_CPU=n.
 */
static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
					    const char *name,
					    int (*startup)(unsigned int cpu),
					    int (*teardown)(unsigned int cpu))
{ … }

/**
 * 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,
						     const char *name,
						     int (*startup)(unsigned int cpu),
						     int (*teardown)(unsigned int cpu))
{ … }

/**
 * cpuhp_setup_state_multi - Add callbacks for multi state
 * @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
 *
 * 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
 * invoked once an instance for this state are registered via
 * cpuhp_state_add_instance() or cpuhp_state_add_instance_nocalls()
 */
static inline int cpuhp_setup_state_multi(enum cpuhp_state state,
					  const char *name,
					  int (*startup)(unsigned int cpu,
							 struct hlist_node *node),
					  int (*teardown)(unsigned int cpu,
							  struct hlist_node *node))
{ … }

int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
			       bool invoke);
int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
					  struct hlist_node *node, bool invoke);

/**
 * cpuhp_state_add_instance - Add an instance for a state and invoke startup
 *                            callback.
 * @state:	The state for which the instance is installed
 * @node:	The node for this individual state.
 *
 * Installs the instance for the @state and invokes the registered startup
 * callback on the online cpus which have already reached the @state. The
 * @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,
					   struct hlist_node *node)
{ … }

/**
 * cpuhp_state_add_instance_nocalls - Add an instance for a state without
 *                                    invoking the startup callback.
 * @state:	The state for which the instance is installed
 * @node:	The node for this individual state.
 *
 * Installs the instance for the @state. The @state must have been earlier
 * 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,
						   struct hlist_node *node)
{ … }

/**
 * 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
cpuhp_state_add_instance_nocalls_cpuslocked(enum cpuhp_state state,
					    struct hlist_node *node)
{ … }

void __cpuhp_remove_state(enum cpuhp_state state, bool invoke);
void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke);

/**
 * cpuhp_remove_state - Remove hotplug state callbacks and invoke the teardown
 * @state:	The state for which the calls are removed
 *
 * Removes the callback functions and invokes the teardown callback on
 * the online cpus which have already reached the @state.
 */
static inline void cpuhp_remove_state(enum cpuhp_state state)
{ … }

/**
 * cpuhp_remove_state_nocalls - Remove hotplug state callbacks without invoking
 *				the teardown callback
 * @state:	The state for which the calls are removed
 */
static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state)
{ … }

/**
 * 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)
{ … }

/**
 * cpuhp_remove_multi_state - Remove hotplug multi state callback
 * @state:	The state for which the calls are removed
 *
 * Removes the callback functions from a multi state. This is the reverse of
 * cpuhp_setup_state_multi(). All instances should have been removed before
 * invoking this function.
 */
static inline void cpuhp_remove_multi_state(enum cpuhp_state state)
{ … }

int __cpuhp_state_remove_instance(enum cpuhp_state state,
				  struct hlist_node *node, bool invoke);

/**
 * cpuhp_state_remove_instance - Remove hotplug instance from state and invoke
 *                               the teardown callback
 * @state:	The state from which the instance is removed
 * @node:	The node for this individual state.
 *
 * Removes the instance and invokes the teardown callback on the online cpus
 * which have already reached @state.
 */
static inline int cpuhp_state_remove_instance(enum cpuhp_state state,
					      struct hlist_node *node)
{ … }

/**
 * cpuhp_state_remove_instance_nocalls - Remove hotplug instance from state
 *					 without invoking the teardown callback
 * @state:	The state from which the instance is removed
 * @node:	The node for this individual state.
 *
 * Removes the instance without invoking the teardown callback.
 */
static inline int cpuhp_state_remove_instance_nocalls(enum cpuhp_state state,
						      struct hlist_node *node)
{ … }

#ifdef CONFIG_SMP
void cpuhp_online_idle(enum cpuhp_state state);
#else
static inline void cpuhp_online_idle(enum cpuhp_state state) { }
#endif

struct task_struct;

void cpuhp_ap_sync_alive(void);
void arch_cpuhp_sync_state_poll(void);
void arch_cpuhp_cleanup_kick_cpu(unsigned int cpu);
int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *tidle);
bool arch_cpuhp_init_parallel_bringup(void);

#ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
void cpuhp_ap_report_dead(void);
void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu);
#else
static inline void cpuhp_ap_report_dead(void) { }
static inline void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
#endif

#endif
linux/include/linux/cpuhotplug.h
