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()

Author: torvalds

Documentation/core-api/cpu_hotplug.rst

@@ -43,7 +43,7 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
 	this_leaf->type = type;
 }
 
-static int __init_cache_level(unsigned int cpu)
+int init_cache_level(unsigned int cpu)
 {
 	unsigned int ctype, level, leaves, fw_level;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
@@ -78,7 +78,7 @@ static int __init_cache_level(unsigned int cpu)
 	return 0;
 }
 
-static int __populate_cache_leaves(unsigned int cpu)
+int populate_cache_leaves(unsigned int cpu)
 {
 	unsigned int level, idx;
 	enum cache_type type;
@@ -97,6 +97,3 @@ static int __populate_cache_leaves(unsigned int cpu)
 	}
 	return 0;
 }
-
-DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
-DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)

arch/arm64/kernel/cacheinfo.c

@@ -17,7 +17,7 @@ do {								\
 	leaf++;							\
 } while (0)
 
-static int __init_cache_level(unsigned int cpu)
+int init_cache_level(unsigned int cpu)
 {
 	struct cpuinfo_mips *c = &current_cpu_data;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
@@ -74,7 +74,7 @@ static void fill_cpumask_cluster(int cpu, cpumask_t *cpu_map)
 			cpumask_set_cpu(cpu1, cpu_map);
 }
 
-static int __populate_cache_leaves(unsigned int cpu)
+int populate_cache_leaves(unsigned int cpu)
 {
 	struct cpuinfo_mips *c = &current_cpu_data;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
@@ -114,6 +114,3 @@ static int __populate_cache_leaves(unsigned int cpu)
 
 	return 0;
 }
-
-DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
-DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)

arch/mips/kernel/cacheinfo.c

@@ -113,7 +113,7 @@ static void fill_cacheinfo(struct cacheinfo **this_leaf,
 	}
 }
 
-static int __init_cache_level(unsigned int cpu)
+int init_cache_level(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct device_node *np = of_cpu_device_node_get(cpu);
@@ -155,7 +155,7 @@ static int __init_cache_level(unsigned int cpu)
 	return 0;
 }
 
-static int __populate_cache_leaves(unsigned int cpu)
+int populate_cache_leaves(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct cacheinfo *this_leaf = this_cpu_ci->info_list;
@@ -187,6 +187,3 @@ static int __populate_cache_leaves(unsigned int cpu)
 
 	return 0;
 }
-
-DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
-DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)

arch/riscv/kernel/cacheinfo.c

@@ -985,7 +985,7 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
 	this_leaf->priv = base->nb;
 }
 
-static int __init_cache_level(unsigned int cpu)
+int init_cache_level(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 
@@ -1014,7 +1014,7 @@ static void get_cache_id(int cpu, struct _cpuid4_info_regs *id4_regs)
 	id4_regs->id = c->apicid >> index_msb;
 }
 
-static int __populate_cache_leaves(unsigned int cpu)
+int populate_cache_leaves(unsigned int cpu)
 {
 	unsigned int idx, ret;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
@@ -1033,6 +1033,3 @@ static int __populate_cache_leaves(unsigned int cpu)
 
 	return 0;
 }
-
-DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
-DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)

arch/x86/kernel/cpu/cacheinfo.c

@@ -79,24 +79,6 @@ struct cpu_cacheinfo {
 	bool cpu_map_populated;
 };
 
-/*
- * Helpers to make sure "func" is executed on the cpu whose cache
- * attributes are being detected
- */
-#define DEFINE_SMP_CALL_CACHE_FUNCTION(func)			\
-static inline void _##func(void *ret)				\
-{								\
-	int cpu = smp_processor_id();				\
-	*(int *)ret = __##func(cpu);				\
-}								\
-								\
-int func(unsigned int cpu)					\
-{								\
-	int ret;						\
-	smp_call_function_single(cpu, _##func, &ret, true);	\
-	return ret;						\
-}
-
 struct cpu_cacheinfo *get_cpu_cacheinfo(unsigned int cpu);
 int init_cache_level(unsigned int cpu);
 int populate_cache_leaves(unsigned int cpu);

include/linux/cacheinfo.h

@@ -143,12 +143,6 @@ static inline int remove_cpu(unsigned int cpu) { return -EPERM; }
 static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { }
 #endif	/* !CONFIG_HOTPLUG_CPU */
 
-/* Wrappers which go away once all code is converted */
-static inline void cpu_hotplug_begin(void) { cpus_write_lock(); }
-static inline void cpu_hotplug_done(void) { cpus_write_unlock(); }
-static inline void get_online_cpus(void) { cpus_read_lock(); }
-static inline void put_online_cpus(void) { cpus_read_unlock(); }
-
 #ifdef CONFIG_PM_SLEEP_SMP
 extern int freeze_secondary_cpus(int primary);
 extern void thaw_secondary_cpus(void);

include/linux/cpu.h

@@ -22,8 +22,42 @@
  *              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 {
 	CPUHP_INVALID = -1,
+
+	/* PREPARE section invoked on a control CPU */
 	CPUHP_OFFLINE = 0,
 	CPUHP_CREATE_THREADS,
 	CPUHP_PERF_PREPARE,
@@ -95,6 +129,11 @@ enum cpuhp_state {
 	CPUHP_BP_PREPARE_DYN,
 	CPUHP_BP_PREPARE_DYN_END		= CPUHP_BP_PREPARE_DYN + 20,
 	CPUHP_BRINGUP_CPU,
+
+	/*
+	 * STARTING section invoked on the hotplugged CPU in low level
+	 * bringup and teardown code.
+	 */
 	CPUHP_AP_IDLE_DEAD,
 	CPUHP_AP_OFFLINE,
 	CPUHP_AP_SCHED_STARTING,
@@ -155,6 +194,8 @@ enum cpuhp_state {
 	CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,
+
+	/* Online section invoked on the hotplugged CPU from the hotplug thread */
 	CPUHP_AP_ONLINE_IDLE,
 	CPUHP_AP_SCHED_WAIT_EMPTY,
 	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),
 				   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
  * @name:	Name of the callback (will be used in debug output)
- * @startup:	startup callback function
- * @teardown:	teardown callback function
+ * @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 present cpus which have already reached the @state.
+ * 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,
@@ -233,6 +275,18 @@ static inline int cpuhp_setup_state(enum cpuhp_state state,
 	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,
 					       const char *name,
 					       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
- *			       callbacks
+ *			       @startup callback
  * @state:	The state for which the calls are installed
  * @name:	Name of the callback.
- * @startup:	startup callback function
- * @teardown:	teardown callback function
+ * @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 no calls are executed are invoked
- * during installation of this callback. NOP if SMP=n or HOTPLUG_CPU=n.
+ * 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,
@@ -262,6 +316,19 @@ static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
 				   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,
 						     const char *name,
 						     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
  * @state:	The state for which the calls are installed
  * @name:	Name of the callback.
- * @startup:	startup callback function
- * @teardown:	teardown callback function
+ * @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.
+ * cpuhp_state_add_instance() or cpuhp_state_add_instance_nocalls()
  */
 static inline int cpuhp_setup_state_multi(enum cpuhp_state state,
 					  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
  * @node:	The node for this individual state.
  *
- * Installs the instance for the @state and invokes the startup callback on
- * the present cpus which have already reached the @state. The @state must have
- * been earlier marked as multi-instance by @cpuhp_setup_state_multi.
+ * 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)
@@ -322,15 +390,27 @@ static inline int cpuhp_state_add_instance(enum cpuhp_state state,
  * @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.
+ * 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)
 {
 	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
 cpuhp_state_add_instance_nocalls_cpuslocked(enum cpuhp_state state,
 					    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
  *
  * 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)
 {
@@ -355,14 +435,22 @@ static inline void cpuhp_remove_state(enum cpuhp_state state)
 
 /**
  * cpuhp_remove_state_nocalls - Remove hotplug state callbacks without invoking
- *				teardown
+ *				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(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)
 {
 	__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
  * @node:	The node for this individual state.
  *
- * Removes the instance and invokes the teardown callback on the present cpus
- * which have already reached the @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)