cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions

hotcpu_notifier(), cpu_notifier(), __hotcpu_notifier(), __cpu_notifier(),
register_hotcpu_notifier(), register_cpu_notifier(),
__register_hotcpu_notifier(), __register_cpu_notifier(),
unregister_hotcpu_notifier(), unregister_cpu_notifier(),
__unregister_hotcpu_notifier(), __unregister_cpu_notifier()

are unused now. Remove them and all related code.

Remove also the now pointless cpu notifier error injection mechanism. The
states can be executed step by step and error rollback is the same as cpu
down, so any state transition can be tested w/o requiring the notifier
error injection.

Some CPU hotplug states are kept as they are (ab)used for hotplug state
tracking.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161221192112.005642358@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/cpu.h

@@ -57,9 +57,6 @@ struct notifier_block;
 
 #define CPU_ONLINE		0x0002 /* CPU (unsigned)v is up */
 #define CPU_UP_PREPARE		0x0003 /* CPU (unsigned)v coming up */
-#define CPU_UP_CANCELED		0x0004 /* CPU (unsigned)v NOT coming up */
-#define CPU_DOWN_PREPARE	0x0005 /* CPU (unsigned)v going down */
-#define CPU_DOWN_FAILED		0x0006 /* CPU (unsigned)v NOT going down */
 #define CPU_DEAD		0x0007 /* CPU (unsigned)v dead */
 #define CPU_POST_DEAD		0x0009 /* CPU (unsigned)v dead, cpu_hotplug
 					* lock is dropped */
@@ -80,80 +77,14 @@ struct notifier_block;
 
 #ifdef CONFIG_SMP
 extern bool cpuhp_tasks_frozen;
-/* Need to know about CPUs going up/down? */
-#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
-#define cpu_notifier(fn, pri) {					\
-	static struct notifier_block fn##_nb =			\
-		{ .notifier_call = fn, .priority = pri };	\
-	register_cpu_notifier(&fn##_nb);			\
-}
-
-#define __cpu_notifier(fn, pri) {				\
-	static struct notifier_block fn##_nb =			\
-		{ .notifier_call = fn, .priority = pri };	\
-	__register_cpu_notifier(&fn##_nb);			\
-}
-
-extern int register_cpu_notifier(struct notifier_block *nb);
-extern int __register_cpu_notifier(struct notifier_block *nb);
-extern void unregister_cpu_notifier(struct notifier_block *nb);
-extern void __unregister_cpu_notifier(struct notifier_block *nb);
-
-#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
-#define cpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-#define __cpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-
-static inline int register_cpu_notifier(struct notifier_block *nb)
-{
-	return 0;
-}
-
-static inline int __register_cpu_notifier(struct notifier_block *nb)
-{
-	return 0;
-}
-
-static inline void unregister_cpu_notifier(struct notifier_block *nb)
-{
-}
-
-static inline void __unregister_cpu_notifier(struct notifier_block *nb)
-{
-}
-#endif
-
 int cpu_up(unsigned int cpu);
 void notify_cpu_starting(unsigned int cpu);
 extern void cpu_maps_update_begin(void);
 extern void cpu_maps_update_done(void);
 
-#define cpu_notifier_register_begin	cpu_maps_update_begin
-#define cpu_notifier_register_done	cpu_maps_update_done
-
 #else	/* CONFIG_SMP */
 #define cpuhp_tasks_frozen	0
 
-#define cpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-#define __cpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-
-static inline int register_cpu_notifier(struct notifier_block *nb)
-{
-	return 0;
-}
-
-static inline int __register_cpu_notifier(struct notifier_block *nb)
-{
-	return 0;
-}
-
-static inline void unregister_cpu_notifier(struct notifier_block *nb)
-{
-}
-
-static inline void __unregister_cpu_notifier(struct notifier_block *nb)
-{
-}
-
 static inline void cpu_maps_update_begin(void)
 {
 }
@@ -162,14 +93,6 @@ static inline void cpu_maps_update_done(void)
 {
 }
 
-static inline void cpu_notifier_register_begin(void)
-{
-}
-
-static inline void cpu_notifier_register_done(void)
-{
-}
-
 #endif /* CONFIG_SMP */
 extern struct bus_type cpu_subsys;
 
@@ -182,12 +105,6 @@ extern void get_online_cpus(void);
 extern void put_online_cpus(void);
 extern void cpu_hotplug_disable(void);
 extern void cpu_hotplug_enable(void);
-#define hotcpu_notifier(fn, pri)	cpu_notifier(fn, pri)
-#define __hotcpu_notifier(fn, pri)	__cpu_notifier(fn, pri)
-#define register_hotcpu_notifier(nb)	register_cpu_notifier(nb)
-#define __register_hotcpu_notifier(nb)	__register_cpu_notifier(nb)
-#define unregister_hotcpu_notifier(nb)	unregister_cpu_notifier(nb)
-#define __unregister_hotcpu_notifier(nb)	__unregister_cpu_notifier(nb)
 void clear_tasks_mm_cpumask(int cpu);
 int cpu_down(unsigned int cpu);
 
@@ -199,13 +116,6 @@ static inline void cpu_hotplug_done(void) {}
 #define put_online_cpus()	do { } while (0)
 #define cpu_hotplug_disable()	do { } while (0)
 #define cpu_hotplug_enable()	do { } while (0)
-#define hotcpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-#define __hotcpu_notifier(fn, pri)	do { (void)(fn); } while (0)
-/* These aren't inline functions due to a GCC bug. */
-#define register_hotcpu_notifier(nb)	({ (void)(nb); 0; })
-#define __register_hotcpu_notifier(nb)	({ (void)(nb); 0; })
-#define unregister_hotcpu_notifier(nb)	({ (void)(nb); })
-#define __unregister_hotcpu_notifier(nb)	({ (void)(nb); })
 #endif		/* CONFIG_HOTPLUG_CPU */
 
 #ifdef CONFIG_PM_SLEEP_SMP

include/linux/cpuhotplug.h

@@ -59,7 +59,6 @@ enum cpuhp_state {
 	CPUHP_POWERPC_MMU_CTX_PREPARE,
 	CPUHP_XEN_PREPARE,
 	CPUHP_XEN_EVTCHN_PREPARE,
-	CPUHP_NOTIFY_PREPARE,
 	CPUHP_ARM_SHMOBILE_SCU_PREPARE,
 	CPUHP_SH_SH3X_PREPARE,
 	CPUHP_BLK_MQ_PREPARE,
@@ -74,7 +73,6 @@ enum cpuhp_state {
 	CPUHP_KVM_PPC_BOOK3S_PREPARE,
 	CPUHP_ZCOMP_PREPARE,
 	CPUHP_TIMERS_DEAD,
-	CPUHP_NOTF_ERR_INJ_PREPARE,
 	CPUHP_MIPS_SOC_PREPARE,
 	CPUHP_BRINGUP_CPU,
 	CPUHP_AP_IDLE_DEAD,
@@ -145,7 +143,6 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_L2X0_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
-	CPUHP_AP_NOTIFY_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,
 	CPUHP_AP_X86_HPET_ONLINE,

kernel/cpu.c

@@ -183,23 +183,16 @@ EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 /*
  * The following two APIs (cpu_maps_update_begin/done) must be used when
  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
- * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
- * hotplug callback (un)registration performed using __register_cpu_notifier()
- * or __unregister_cpu_notifier().
  */
 void cpu_maps_update_begin(void)
 {
 	mutex_lock(&cpu_add_remove_lock);
 }
-EXPORT_SYMBOL(cpu_notifier_register_begin);
 
 void cpu_maps_update_done(void)
 {
 	mutex_unlock(&cpu_add_remove_lock);
 }
-EXPORT_SYMBOL(cpu_notifier_register_done);
-
-static RAW_NOTIFIER_HEAD(cpu_chain);
 
 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
  * Should always be manipulated under cpu_add_remove_lock
@@ -349,66 +342,7 @@ void cpu_hotplug_enable(void)
 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 #endif	/* CONFIG_HOTPLUG_CPU */
 
-/* Need to know about CPUs going up/down? */
-int register_cpu_notifier(struct notifier_block *nb)
-{
-	int ret;
-	cpu_maps_update_begin();
-	ret = raw_notifier_chain_register(&cpu_chain, nb);
-	cpu_maps_update_done();
-	return ret;
-}
-
-int __register_cpu_notifier(struct notifier_block *nb)
-{
-	return raw_notifier_chain_register(&cpu_chain, nb);
-}
-
-static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
-			int *nr_calls)
-{
-	unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
-	void *hcpu = (void *)(long)cpu;
-
-	int ret;
-
-	ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
-					nr_calls);
-
-	return notifier_to_errno(ret);
-}
-
-static int cpu_notify(unsigned long val, unsigned int cpu)
-{
-	return __cpu_notify(val, cpu, -1, NULL);
-}
-
-static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
-{
-	BUG_ON(cpu_notify(val, cpu));
-}
-
 /* Notifier wrappers for transitioning to state machine */
-static int notify_prepare(unsigned int cpu)
-{
-	int nr_calls = 0;
-	int ret;
-
-	ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
-	if (ret) {
-		nr_calls--;
-		printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
-				__func__, cpu);
-		__cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
-	}
-	return ret;
-}
-
-static int notify_online(unsigned int cpu)
-{
-	cpu_notify(CPU_ONLINE, cpu);
-	return 0;
-}
 
 static int bringup_wait_for_ap(unsigned int cpu)
 {
@@ -433,10 +367,8 @@ static int bringup_cpu(unsigned int cpu)
 	/* Arch-specific enabling code. */
 	ret = __cpu_up(cpu, idle);
 	irq_unlock_sparse();
-	if (ret) {
+	if (ret)
-		cpu_notify(CPU_UP_CANCELED, cpu);
 		return ret;
-	}
 	ret = bringup_wait_for_ap(cpu);
 	BUG_ON(!cpu_online(cpu));
 	return ret;
@@ -565,11 +497,6 @@ static void cpuhp_thread_fun(unsigned int cpu)
 		BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 
 		undo_cpu_down(cpu, st);
-		/*
-		 * This is a momentary workaround to keep the notifier users
-		 * happy. Will go away once we got rid of the notifiers.
-		 */
-		cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 		st->rollback = false;
 	} else {
 		/* Cannot happen .... */
@@ -659,22 +586,6 @@ void __init cpuhp_threads_init(void)
 	kthread_unpark(this_cpu_read(cpuhp_state.thread));
 }
 
-EXPORT_SYMBOL(register_cpu_notifier);
-EXPORT_SYMBOL(__register_cpu_notifier);
-void unregister_cpu_notifier(struct notifier_block *nb)
-{
-	cpu_maps_update_begin();
-	raw_notifier_chain_unregister(&cpu_chain, nb);
-	cpu_maps_update_done();
-}
-EXPORT_SYMBOL(unregister_cpu_notifier);
-
-void __unregister_cpu_notifier(struct notifier_block *nb)
-{
-	raw_notifier_chain_unregister(&cpu_chain, nb);
-}
-EXPORT_SYMBOL(__unregister_cpu_notifier);
-
 #ifdef CONFIG_HOTPLUG_CPU
 /**
  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
@@ -741,20 +652,6 @@ static inline void check_for_tasks(int dead_cpu)
 	read_unlock(&tasklist_lock);
 }
 
-static int notify_down_prepare(unsigned int cpu)
-{
-	int err, nr_calls = 0;
-
-	err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
-	if (err) {
-		nr_calls--;
-		__cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
-		pr_warn("%s: attempt to take down CPU %u failed\n",
-				__func__, cpu);
-	}
-	return err;
-}
-
 /* Take this CPU down. */
 static int take_cpu_down(void *_param)
 {
@@ -833,13 +730,6 @@ static int takedown_cpu(unsigned int cpu)
 	return 0;
 }
 
-static int notify_dead(unsigned int cpu)
-{
-	cpu_notify_nofail(CPU_DEAD, cpu);
-	check_for_tasks(cpu);
-	return 0;
-}
-
 static void cpuhp_complete_idle_dead(void *arg)
 {
 	struct cpuhp_cpu_state *st = arg;
@@ -863,9 +753,7 @@ void cpuhp_report_idle_dead(void)
 }
 
 #else
-#define notify_down_prepare	NULL
 #define takedown_cpu		NULL
-#define notify_dead		NULL
 #endif
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -924,9 +812,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 	hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
 out:
 	cpu_hotplug_done();
-	/* This post dead nonsense must die */
-	if (!ret && hasdied)
-		cpu_notify_nofail(CPU_POST_DEAD, cpu);
 	return ret;
 }
 
@@ -1291,17 +1176,6 @@ static struct cpuhp_step cpuhp_bp_states[] = {
 		.startup.single		= rcutree_prepare_cpu,
 		.teardown.single	= rcutree_dead_cpu,
 	},
-	/*
-	 * Preparatory and dead notifiers. Will be replaced once the notifiers
-	 * are converted to states.
-	 */
-	[CPUHP_NOTIFY_PREPARE] = {
-		.name			= "notify:prepare",
-		.startup.single		= notify_prepare,
-		.teardown.single	= notify_dead,
-		.skip_onerr		= true,
-		.cant_stop		= true,
-	},
 	/*
 	 * On the tear-down path, timers_dead_cpu() must be invoked
 	 * before blk_mq_queue_reinit_notify() from notify_dead(),
@@ -1391,17 +1265,6 @@ static struct cpuhp_step cpuhp_ap_states[] = {
 		.startup.single		= rcutree_online_cpu,
 		.teardown.single	= rcutree_offline_cpu,
 	},
-
-	/*
-	 * Online/down_prepare notifiers. Will be removed once the notifiers
-	 * are converted to states.
-	 */
-	[CPUHP_AP_NOTIFY_ONLINE] = {
-		.name			= "notify:online",
-		.startup.single		= notify_online,
-		.teardown.single	= notify_down_prepare,
-		.skip_onerr		= true,
-	},
 #endif
 	/*
 	 * The dynamically registered state space is here

lib/Kconfig.debug

@@ -1538,30 +1538,6 @@ config NOTIFIER_ERROR_INJECTION
 
 	  Say N if unsure.
 
-config CPU_NOTIFIER_ERROR_INJECT
-	tristate "CPU notifier error injection module"
-	depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
-	help
-	  This option provides a kernel module that can be used to test
-	  the error handling of the cpu notifiers by injecting artificial
-	  errors to CPU notifier chain callbacks.  It is controlled through
-	  debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
-
-	  If the notifier call chain should be failed with some events
-	  notified, write the error code to "actions/<notifier event>/error".
-
-	  Example: Inject CPU offline error (-1 == -EPERM)
-
-	  # cd /sys/kernel/debug/notifier-error-inject/cpu
-	  # echo -1 > actions/CPU_DOWN_PREPARE/error
-	  # echo 0 > /sys/devices/system/cpu/cpu1/online
-	  bash: echo: write error: Operation not permitted
-
-	  To compile this code as a module, choose M here: the module will
-	  be called cpu-notifier-error-inject.
-
-	  If unsure, say N.
-
 config PM_NOTIFIER_ERROR_INJECT
 	tristate "PM notifier error injection module"
 	depends on PM && NOTIFIER_ERROR_INJECTION

lib/Makefile

@@ -128,7 +128,6 @@ obj-$(CONFIG_SWIOTLB) += swiotlb.o
 obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o iommu-common.o
 obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
 obj-$(CONFIG_NOTIFIER_ERROR_INJECTION) += notifier-error-inject.o
-obj-$(CONFIG_CPU_NOTIFIER_ERROR_INJECT) += cpu-notifier-error-inject.o
 obj-$(CONFIG_PM_NOTIFIER_ERROR_INJECT) += pm-notifier-error-inject.o
 obj-$(CONFIG_NETDEV_NOTIFIER_ERROR_INJECT) += netdev-notifier-error-inject.o
 obj-$(CONFIG_MEMORY_NOTIFIER_ERROR_INJECT) += memory-notifier-error-inject.o

lib/cpu-notifier-error-inject.c

@@ -1,84 +0,0 @@
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/cpu.h>
-
-#include "notifier-error-inject.h"
-
-static int priority;
-module_param(priority, int, 0);
-MODULE_PARM_DESC(priority, "specify cpu notifier priority");
-
-#define UP_PREPARE 0
-#define UP_PREPARE_FROZEN 0
-#define DOWN_PREPARE 0
-#define DOWN_PREPARE_FROZEN 0
-
-static struct notifier_err_inject cpu_notifier_err_inject = {
-	.actions = {
-		{ NOTIFIER_ERR_INJECT_ACTION(UP_PREPARE) },
-		{ NOTIFIER_ERR_INJECT_ACTION(UP_PREPARE_FROZEN) },
-		{ NOTIFIER_ERR_INJECT_ACTION(DOWN_PREPARE) },
-		{ NOTIFIER_ERR_INJECT_ACTION(DOWN_PREPARE_FROZEN) },
-		{}
-	}
-};
-
-static int notf_err_handle(struct notifier_err_inject_action *action)
-{
-	int ret;
-
-	ret = action->error;
-	if (ret)
-		pr_info("Injecting error (%d) to %s\n", ret, action->name);
-	return ret;
-}
-
-static int notf_err_inj_up_prepare(unsigned int cpu)
-{
-	if (!cpuhp_tasks_frozen)
-		return notf_err_handle(&cpu_notifier_err_inject.actions[0]);
-	else
-		return notf_err_handle(&cpu_notifier_err_inject.actions[1]);
-}
-
-static int notf_err_inj_dead(unsigned int cpu)
-{
-	if (!cpuhp_tasks_frozen)
-		return notf_err_handle(&cpu_notifier_err_inject.actions[2]);
-	else
-		return notf_err_handle(&cpu_notifier_err_inject.actions[3]);
-}
-
-static struct dentry *dir;
-
-static int err_inject_init(void)
-{
-	int err;
-
-	dir = notifier_err_inject_init("cpu", notifier_err_inject_dir,
-					&cpu_notifier_err_inject, priority);
-	if (IS_ERR(dir))
-		return PTR_ERR(dir);
-
-	err = cpuhp_setup_state_nocalls(CPUHP_NOTF_ERR_INJ_PREPARE,
-					"cpu-err-notif:prepare",
-					notf_err_inj_up_prepare,
-					notf_err_inj_dead);
-	if (err)
-		debugfs_remove_recursive(dir);
-
-	return err;
-}
-
-static void err_inject_exit(void)
-{
-	cpuhp_remove_state_nocalls(CPUHP_NOTF_ERR_INJ_PREPARE);
-	debugfs_remove_recursive(dir);
-}
-
-module_init(err_inject_init);
-module_exit(err_inject_exit);
-
-MODULE_DESCRIPTION("CPU notifier error injection module");
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");