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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __CPUHOTPLUG_H
3#define __CPUHOTPLUG_H
4
5#include <linux/types.h>
6
7/*
8 * CPU-up CPU-down
9 *
10 * BP AP BP AP
11 *
12 * OFFLINE OFFLINE
13 * | ^
14 * v |
15 * BRINGUP_CPU->AP_OFFLINE BRINGUP_CPU <- AP_IDLE_DEAD (idle thread/play_dead)
16 * | AP_OFFLINE
17 * v (IRQ-off) ,---------------^
18 * AP_ONLNE | (stop_machine)
19 * | TEARDOWN_CPU <- AP_ONLINE_IDLE
20 * | ^
21 * v |
22 * AP_ACTIVE AP_ACTIVE
23 */
24
25/*
26 * CPU hotplug states. The state machine invokes the installed state
27 * startup callbacks sequentially from CPUHP_OFFLINE + 1 to CPUHP_ONLINE
28 * during a CPU online operation. During a CPU offline operation the
29 * installed teardown callbacks are invoked in the reverse order from
30 * CPUHP_ONLINE - 1 down to CPUHP_OFFLINE.
31 *
32 * The state space has three sections: PREPARE, STARTING and ONLINE.
33 *
34 * PREPARE: The callbacks are invoked on a control CPU before the
35 * hotplugged CPU is started up or after the hotplugged CPU has died.
36 *
37 * STARTING: The callbacks are invoked on the hotplugged CPU from the low level
38 * hotplug startup/teardown code with interrupts disabled.
39 *
40 * ONLINE: The callbacks are invoked on the hotplugged CPU from the per CPU
41 * hotplug thread with interrupts and preemption enabled.
42 *
43 * Adding explicit states to this enum is only necessary when:
44 *
45 * 1) The state is within the STARTING section
46 *
47 * 2) The state has ordering constraints vs. other states in the
48 * same section.
49 *
50 * If neither #1 nor #2 apply, please use the dynamic state space when
51 * setting up a state by using CPUHP_BP_PREPARE_DYN or CPUHP_AP_ONLINE_DYN
52 * for the @state argument of the setup function.
53 *
54 * See Documentation/core-api/cpu_hotplug.rst for further information and
55 * examples.
56 */
57enum cpuhp_state {
58 CPUHP_INVALID = -1,
59
60 /* PREPARE section invoked on a control CPU */
61 CPUHP_OFFLINE = 0,
62 CPUHP_CREATE_THREADS,
63 CPUHP_PERF_X86_PREPARE,
64 CPUHP_PERF_X86_AMD_UNCORE_PREP,
65 CPUHP_PERF_POWER,
66 CPUHP_PERF_SUPERH,
67 CPUHP_X86_HPET_DEAD,
68 CPUHP_X86_MCE_DEAD,
69 CPUHP_VIRT_NET_DEAD,
70 CPUHP_IBMVNIC_DEAD,
71 CPUHP_SLUB_DEAD,
72 CPUHP_DEBUG_OBJ_DEAD,
73 CPUHP_MM_WRITEBACK_DEAD,
74 CPUHP_MM_VMSTAT_DEAD,
75 CPUHP_SOFTIRQ_DEAD,
76 CPUHP_NET_MVNETA_DEAD,
77 CPUHP_CPUIDLE_DEAD,
78 CPUHP_ARM64_FPSIMD_DEAD,
79 CPUHP_ARM_OMAP_WAKE_DEAD,
80 CPUHP_IRQ_POLL_DEAD,
81 CPUHP_BLOCK_SOFTIRQ_DEAD,
82 CPUHP_BIO_DEAD,
83 CPUHP_ACPI_CPUDRV_DEAD,
84 CPUHP_S390_PFAULT_DEAD,
85 CPUHP_BLK_MQ_DEAD,
86 CPUHP_FS_BUFF_DEAD,
87 CPUHP_PRINTK_DEAD,
88 CPUHP_MM_MEMCQ_DEAD,
89 CPUHP_PERCPU_CNT_DEAD,
90 CPUHP_RADIX_DEAD,
91 CPUHP_PAGE_ALLOC,
92 CPUHP_NET_DEV_DEAD,
93 CPUHP_IOMMU_IOVA_DEAD,
94 CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
95 CPUHP_PADATA_DEAD,
96 CPUHP_AP_DTPM_CPU_DEAD,
97 CPUHP_RANDOM_PREPARE,
98 CPUHP_WORKQUEUE_PREP,
99 CPUHP_POWER_NUMA_PREPARE,
100 CPUHP_HRTIMERS_PREPARE,
101 CPUHP_X2APIC_PREPARE,
102 CPUHP_SMPCFD_PREPARE,
103 CPUHP_RELAY_PREPARE,
104 CPUHP_MD_RAID5_PREPARE,
105 CPUHP_RCUTREE_PREP,
106 CPUHP_CPUIDLE_COUPLED_PREPARE,
107 CPUHP_POWERPC_PMAC_PREPARE,
108 CPUHP_POWERPC_MMU_CTX_PREPARE,
109 CPUHP_XEN_PREPARE,
110 CPUHP_XEN_EVTCHN_PREPARE,
111 CPUHP_ARM_SHMOBILE_SCU_PREPARE,
112 CPUHP_SH_SH3X_PREPARE,
113 CPUHP_TOPOLOGY_PREPARE,
114 CPUHP_NET_IUCV_PREPARE,
115 CPUHP_ARM_BL_PREPARE,
116 CPUHP_TRACE_RB_PREPARE,
117 CPUHP_MM_ZSWP_POOL_PREPARE,
118 CPUHP_KVM_PPC_BOOK3S_PREPARE,
119 CPUHP_ZCOMP_PREPARE,
120 CPUHP_TIMERS_PREPARE,
121 CPUHP_TMIGR_PREPARE,
122 CPUHP_MIPS_SOC_PREPARE,
123 CPUHP_BP_PREPARE_DYN,
124 CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20,
125 CPUHP_BP_KICK_AP,
126 CPUHP_BRINGUP_CPU,
127
128 /*
129 * STARTING section invoked on the hotplugged CPU in low level
130 * bringup and teardown code.
131 */
132 CPUHP_AP_IDLE_DEAD,
133 CPUHP_AP_OFFLINE,
134 CPUHP_AP_CACHECTRL_STARTING,
135 CPUHP_AP_SCHED_STARTING,
136 CPUHP_AP_RCUTREE_DYING,
137 CPUHP_AP_CPU_PM_STARTING,
138 CPUHP_AP_IRQ_GIC_STARTING,
139 CPUHP_AP_IRQ_HIP04_STARTING,
140 CPUHP_AP_IRQ_APPLE_AIC_STARTING,
141 CPUHP_AP_IRQ_ARMADA_XP_STARTING,
142 CPUHP_AP_IRQ_BCM2836_STARTING,
143 CPUHP_AP_IRQ_MIPS_GIC_STARTING,
144 CPUHP_AP_IRQ_EIOINTC_STARTING,
145 CPUHP_AP_IRQ_AVECINTC_STARTING,
146 CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
147 CPUHP_AP_IRQ_ACLINT_SSWI_STARTING,
148 CPUHP_AP_IRQ_RISCV_IMSIC_STARTING,
149 CPUHP_AP_IRQ_RISCV_SBI_IPI_STARTING,
150 CPUHP_AP_ARM_MVEBU_COHERENCY,
151 CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
152 CPUHP_AP_PERF_X86_STARTING,
153 CPUHP_AP_PERF_X86_AMD_IBS_STARTING,
154 CPUHP_AP_PERF_XTENSA_STARTING,
155 CPUHP_AP_ARM_VFP_STARTING,
156 CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
157 CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
158 CPUHP_AP_PERF_ARM_ACPI_STARTING,
159 CPUHP_AP_PERF_ARM_STARTING,
160 CPUHP_AP_PERF_RISCV_STARTING,
161 CPUHP_AP_ARM_L2X0_STARTING,
162 CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
163 CPUHP_AP_ARM_ARCH_TIMER_STARTING,
164 CPUHP_AP_ARM_ARCH_TIMER_EVTSTRM_STARTING,
165 CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
166 CPUHP_AP_JCORE_TIMER_STARTING,
167 CPUHP_AP_ARM_TWD_STARTING,
168 CPUHP_AP_QCOM_TIMER_STARTING,
169 CPUHP_AP_TEGRA_TIMER_STARTING,
170 CPUHP_AP_ARMADA_TIMER_STARTING,
171 CPUHP_AP_LOONGARCH_ARCH_TIMER_STARTING,
172 CPUHP_AP_MIPS_GIC_TIMER_STARTING,
173 CPUHP_AP_ARC_TIMER_STARTING,
174 CPUHP_AP_REALTEK_TIMER_STARTING,
175 CPUHP_AP_RISCV_TIMER_STARTING,
176 CPUHP_AP_CLINT_TIMER_STARTING,
177 CPUHP_AP_CSKY_TIMER_STARTING,
178 CPUHP_AP_TI_GP_TIMER_STARTING,
179 CPUHP_AP_HYPERV_TIMER_STARTING,
180 /* Must be the last timer callback */
181 CPUHP_AP_DUMMY_TIMER_STARTING,
182 CPUHP_AP_ARM_XEN_STARTING,
183 CPUHP_AP_ARM_XEN_RUNSTATE_STARTING,
184 CPUHP_AP_ARM_CORESIGHT_STARTING,
185 CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
186 CPUHP_AP_ARM64_ISNDEP_STARTING,
187 CPUHP_AP_SMPCFD_DYING,
188 CPUHP_AP_HRTIMERS_DYING,
189 CPUHP_AP_TICK_DYING,
190 CPUHP_AP_X86_TBOOT_DYING,
191 CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
192 CPUHP_AP_ONLINE,
193 CPUHP_TEARDOWN_CPU,
194
195 /* Online section invoked on the hotplugged CPU from the hotplug thread */
196 CPUHP_AP_ONLINE_IDLE,
197 CPUHP_AP_HYPERV_ONLINE,
198 CPUHP_AP_KVM_ONLINE,
199 CPUHP_AP_SCHED_WAIT_EMPTY,
200 CPUHP_AP_SMPBOOT_THREADS,
201 CPUHP_AP_IRQ_AFFINITY_ONLINE,
202 CPUHP_AP_BLK_MQ_ONLINE,
203 CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
204 CPUHP_AP_X86_INTEL_EPB_ONLINE,
205 CPUHP_AP_PERF_ONLINE,
206 CPUHP_AP_PERF_X86_ONLINE,
207 CPUHP_AP_PERF_X86_UNCORE_ONLINE,
208 CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
209 CPUHP_AP_PERF_X86_AMD_POWER_ONLINE,
210 CPUHP_AP_PERF_S390_CF_ONLINE,
211 CPUHP_AP_PERF_S390_SF_ONLINE,
212 CPUHP_AP_PERF_ARM_CCI_ONLINE,
213 CPUHP_AP_PERF_ARM_CCN_ONLINE,
214 CPUHP_AP_PERF_ARM_HISI_CPA_ONLINE,
215 CPUHP_AP_PERF_ARM_HISI_DDRC_ONLINE,
216 CPUHP_AP_PERF_ARM_HISI_HHA_ONLINE,
217 CPUHP_AP_PERF_ARM_HISI_L3_ONLINE,
218 CPUHP_AP_PERF_ARM_HISI_PA_ONLINE,
219 CPUHP_AP_PERF_ARM_HISI_SLLC_ONLINE,
220 CPUHP_AP_PERF_ARM_HISI_PCIE_PMU_ONLINE,
221 CPUHP_AP_PERF_ARM_HNS3_PMU_ONLINE,
222 CPUHP_AP_PERF_ARM_L2X0_ONLINE,
223 CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
224 CPUHP_AP_PERF_ARM_QCOM_L3_ONLINE,
225 CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
226 CPUHP_AP_PERF_ARM_CAVIUM_TX2_UNCORE_ONLINE,
227 CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
228 CPUHP_AP_PERF_ARM_MRVL_PEM_ONLINE,
229 CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
230 CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
231 CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
232 CPUHP_AP_PERF_POWERPC_TRACE_IMC_ONLINE,
233 CPUHP_AP_PERF_POWERPC_HV_24x7_ONLINE,
234 CPUHP_AP_PERF_POWERPC_HV_GPCI_ONLINE,
235 CPUHP_AP_PERF_CSKY_ONLINE,
236 CPUHP_AP_TMIGR_ONLINE,
237 CPUHP_AP_WATCHDOG_ONLINE,
238 CPUHP_AP_WORKQUEUE_ONLINE,
239 CPUHP_AP_RANDOM_ONLINE,
240 CPUHP_AP_RCUTREE_ONLINE,
241 CPUHP_AP_KTHREADS_ONLINE,
242 CPUHP_AP_BASE_CACHEINFO_ONLINE,
243 CPUHP_AP_ONLINE_DYN,
244 CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 40,
245 CPUHP_AP_X86_HPET_ONLINE,
246 CPUHP_AP_X86_KVM_CLK_ONLINE,
247 CPUHP_AP_ACTIVE,
248 CPUHP_ONLINE,
249};
250
251int __cpuhp_setup_state(enum cpuhp_state state, const char *name, bool invoke,
252 int (*startup)(unsigned int cpu),
253 int (*teardown)(unsigned int cpu), bool multi_instance);
254
255int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state, const char *name,
256 bool invoke,
257 int (*startup)(unsigned int cpu),
258 int (*teardown)(unsigned int cpu),
259 bool multi_instance);
260/**
261 * cpuhp_setup_state - Setup hotplug state callbacks with calling the @startup
262 * callback
263 * @state: The state for which the calls are installed
264 * @name: Name of the callback (will be used in debug output)
265 * @startup: startup callback function or NULL if not required
266 * @teardown: teardown callback function or NULL if not required
267 *
268 * Installs the callback functions and invokes the @startup callback on
269 * the online cpus which have already reached the @state.
270 */
271static inline int cpuhp_setup_state(enum cpuhp_state state,
272 const char *name,
273 int (*startup)(unsigned int cpu),
274 int (*teardown)(unsigned int cpu))
275{
276 return __cpuhp_setup_state(state, name, invoke: true, startup, teardown, multi_instance: false);
277}
278
279/**
280 * cpuhp_setup_state_cpuslocked - Setup hotplug state callbacks with calling
281 * @startup callback from a cpus_read_lock()
282 * held region
283 * @state: The state for which the calls are installed
284 * @name: Name of the callback (will be used in debug output)
285 * @startup: startup callback function or NULL if not required
286 * @teardown: teardown callback function or NULL if not required
287 *
288 * Same as cpuhp_setup_state() except that it must be invoked from within a
289 * cpus_read_lock() held region.
290 */
291static inline int cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
292 const char *name,
293 int (*startup)(unsigned int cpu),
294 int (*teardown)(unsigned int cpu))
295{
296 return __cpuhp_setup_state_cpuslocked(state, name, invoke: true, startup,
297 teardown, multi_instance: false);
298}
299
300/**
301 * cpuhp_setup_state_nocalls - Setup hotplug state callbacks without calling the
302 * @startup callback
303 * @state: The state for which the calls are installed
304 * @name: Name of the callback.
305 * @startup: startup callback function or NULL if not required
306 * @teardown: teardown callback function or NULL if not required
307 *
308 * Same as cpuhp_setup_state() except that the @startup callback is not
309 * invoked during installation. NOP if SMP=n or HOTPLUG_CPU=n.
310 */
311static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
312 const char *name,
313 int (*startup)(unsigned int cpu),
314 int (*teardown)(unsigned int cpu))
315{
316 return __cpuhp_setup_state(state, name, invoke: false, startup, teardown,
317 multi_instance: false);
318}
319
320/**
321 * cpuhp_setup_state_nocalls_cpuslocked - Setup hotplug state callbacks without
322 * invoking the @startup callback from
323 * a cpus_read_lock() held region
324 * callbacks
325 * @state: The state for which the calls are installed
326 * @name: Name of the callback.
327 * @startup: startup callback function or NULL if not required
328 * @teardown: teardown callback function or NULL if not required
329 *
330 * Same as cpuhp_setup_state_nocalls() except that it must be invoked from
331 * within a cpus_read_lock() held region.
332 */
333static inline int cpuhp_setup_state_nocalls_cpuslocked(enum cpuhp_state state,
334 const char *name,
335 int (*startup)(unsigned int cpu),
336 int (*teardown)(unsigned int cpu))
337{
338 return __cpuhp_setup_state_cpuslocked(state, name, invoke: false, startup,
339 teardown, multi_instance: false);
340}
341
342/**
343 * cpuhp_setup_state_multi - Add callbacks for multi state
344 * @state: The state for which the calls are installed
345 * @name: Name of the callback.
346 * @startup: startup callback function or NULL if not required
347 * @teardown: teardown callback function or NULL if not required
348 *
349 * Sets the internal multi_instance flag and prepares a state to work as a multi
350 * instance callback. No callbacks are invoked at this point. The callbacks are
351 * invoked once an instance for this state are registered via
352 * cpuhp_state_add_instance() or cpuhp_state_add_instance_nocalls()
353 */
354static inline int cpuhp_setup_state_multi(enum cpuhp_state state,
355 const char *name,
356 int (*startup)(unsigned int cpu,
357 struct hlist_node *node),
358 int (*teardown)(unsigned int cpu,
359 struct hlist_node *node))
360{
361 return __cpuhp_setup_state(state, name, invoke: false,
362 startup: (void *) startup,
363 teardown: (void *) teardown, multi_instance: true);
364}
365
366int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
367 bool invoke);
368int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
369 struct hlist_node *node, bool invoke);
370
371/**
372 * cpuhp_state_add_instance - Add an instance for a state and invoke startup
373 * callback.
374 * @state: The state for which the instance is installed
375 * @node: The node for this individual state.
376 *
377 * Installs the instance for the @state and invokes the registered startup
378 * callback on the online cpus which have already reached the @state. The
379 * @state must have been earlier marked as multi-instance by
380 * cpuhp_setup_state_multi().
381 */
382static inline int cpuhp_state_add_instance(enum cpuhp_state state,
383 struct hlist_node *node)
384{
385 return __cpuhp_state_add_instance(state, node, invoke: true);
386}
387
388/**
389 * cpuhp_state_add_instance_nocalls - Add an instance for a state without
390 * invoking the startup callback.
391 * @state: The state for which the instance is installed
392 * @node: The node for this individual state.
393 *
394 * Installs the instance for the @state. The @state must have been earlier
395 * marked as multi-instance by cpuhp_setup_state_multi. NOP if SMP=n or
396 * HOTPLUG_CPU=n.
397 */
398static inline int cpuhp_state_add_instance_nocalls(enum cpuhp_state state,
399 struct hlist_node *node)
400{
401 return __cpuhp_state_add_instance(state, node, invoke: false);
402}
403
404/**
405 * cpuhp_state_add_instance_nocalls_cpuslocked - Add an instance for a state
406 * without invoking the startup
407 * callback from a cpus_read_lock()
408 * held region.
409 * @state: The state for which the instance is installed
410 * @node: The node for this individual state.
411 *
412 * Same as cpuhp_state_add_instance_nocalls() except that it must be
413 * invoked from within a cpus_read_lock() held region.
414 */
415static inline int
416cpuhp_state_add_instance_nocalls_cpuslocked(enum cpuhp_state state,
417 struct hlist_node *node)
418{
419 return __cpuhp_state_add_instance_cpuslocked(state, node, invoke: false);
420}
421
422void __cpuhp_remove_state(enum cpuhp_state state, bool invoke);
423void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke);
424
425/**
426 * cpuhp_remove_state - Remove hotplug state callbacks and invoke the teardown
427 * @state: The state for which the calls are removed
428 *
429 * Removes the callback functions and invokes the teardown callback on
430 * the online cpus which have already reached the @state.
431 */
432static inline void cpuhp_remove_state(enum cpuhp_state state)
433{
434 __cpuhp_remove_state(state, invoke: true);
435}
436
437/**
438 * cpuhp_remove_state_nocalls - Remove hotplug state callbacks without invoking
439 * the teardown callback
440 * @state: The state for which the calls are removed
441 */
442static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state)
443{
444 __cpuhp_remove_state(state, invoke: false);
445}
446
447/**
448 * cpuhp_remove_state_nocalls_cpuslocked - Remove hotplug state callbacks without invoking
449 * teardown from a cpus_read_lock() held region.
450 * @state: The state for which the calls are removed
451 *
452 * Same as cpuhp_remove_state nocalls() except that it must be invoked
453 * from within a cpus_read_lock() held region.
454 */
455static inline void cpuhp_remove_state_nocalls_cpuslocked(enum cpuhp_state state)
456{
457 __cpuhp_remove_state_cpuslocked(state, invoke: false);
458}
459
460/**
461 * cpuhp_remove_multi_state - Remove hotplug multi state callback
462 * @state: The state for which the calls are removed
463 *
464 * Removes the callback functions from a multi state. This is the reverse of
465 * cpuhp_setup_state_multi(). All instances should have been removed before
466 * invoking this function.
467 */
468static inline void cpuhp_remove_multi_state(enum cpuhp_state state)
469{
470 __cpuhp_remove_state(state, invoke: false);
471}
472
473int __cpuhp_state_remove_instance(enum cpuhp_state state,
474 struct hlist_node *node, bool invoke);
475
476/**
477 * cpuhp_state_remove_instance - Remove hotplug instance from state and invoke
478 * the teardown callback
479 * @state: The state from which the instance is removed
480 * @node: The node for this individual state.
481 *
482 * Removes the instance and invokes the teardown callback on the online cpus
483 * which have already reached @state.
484 */
485static inline int cpuhp_state_remove_instance(enum cpuhp_state state,
486 struct hlist_node *node)
487{
488 return __cpuhp_state_remove_instance(state, node, invoke: true);
489}
490
491/**
492 * cpuhp_state_remove_instance_nocalls - Remove hotplug instance from state
493 * without invoking the teardown callback
494 * @state: The state from which the instance is removed
495 * @node: The node for this individual state.
496 *
497 * Removes the instance without invoking the teardown callback.
498 */
499static inline int cpuhp_state_remove_instance_nocalls(enum cpuhp_state state,
500 struct hlist_node *node)
501{
502 return __cpuhp_state_remove_instance(state, node, invoke: false);
503}
504
505#ifdef CONFIG_SMP
506void cpuhp_online_idle(enum cpuhp_state state);
507#else
508static inline void cpuhp_online_idle(enum cpuhp_state state) { }
509#endif
510
511struct task_struct;
512
513void cpuhp_ap_sync_alive(void);
514void arch_cpuhp_sync_state_poll(void);
515void arch_cpuhp_cleanup_kick_cpu(unsigned int cpu);
516int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *tidle);
517bool arch_cpuhp_init_parallel_bringup(void);
518
519#ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
520void cpuhp_ap_report_dead(void);
521void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu);
522#else
523static inline void cpuhp_ap_report_dead(void) { }
524static inline void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
525#endif
526
527#endif
528

source code of linux/include/linux/cpuhotplug.h