1 // SPDX-License-Identifier: GPL-2.0-only 1 // SPDX-License-Identifier: GPL-2.0-only
2 /* 2 /*
3 * Common SMP CPU bringup/teardown functions 3 * Common SMP CPU bringup/teardown functions
4 */ 4 */
5 #include <linux/cpu.h> 5 #include <linux/cpu.h>
6 #include <linux/err.h> 6 #include <linux/err.h>
7 #include <linux/smp.h> 7 #include <linux/smp.h>
8 #include <linux/delay.h> 8 #include <linux/delay.h>
9 #include <linux/init.h> 9 #include <linux/init.h>
10 #include <linux/list.h> 10 #include <linux/list.h>
11 #include <linux/slab.h> 11 #include <linux/slab.h>
12 #include <linux/sched.h> 12 #include <linux/sched.h>
13 #include <linux/sched/task.h> 13 #include <linux/sched/task.h>
14 #include <linux/export.h> 14 #include <linux/export.h>
15 #include <linux/percpu.h> 15 #include <linux/percpu.h>
16 #include <linux/kthread.h> 16 #include <linux/kthread.h>
17 #include <linux/smpboot.h> 17 #include <linux/smpboot.h>
18 18
19 #include "smpboot.h" 19 #include "smpboot.h"
20 20
21 #ifdef CONFIG_SMP 21 #ifdef CONFIG_SMP
22 22
23 #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD 23 #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
24 /* 24 /*
25 * For the hotplug case we keep the task struc 25 * For the hotplug case we keep the task structs around and reuse
26 * them. 26 * them.
27 */ 27 */
28 static DEFINE_PER_CPU(struct task_struct *, id 28 static DEFINE_PER_CPU(struct task_struct *, idle_threads);
29 29
30 struct task_struct *idle_thread_get(unsigned i 30 struct task_struct *idle_thread_get(unsigned int cpu)
31 { 31 {
32 struct task_struct *tsk = per_cpu(idle 32 struct task_struct *tsk = per_cpu(idle_threads, cpu);
33 33
34 if (!tsk) 34 if (!tsk)
35 return ERR_PTR(-ENOMEM); 35 return ERR_PTR(-ENOMEM);
36 return tsk; 36 return tsk;
37 } 37 }
38 38
39 void __init idle_thread_set_boot_cpu(void) 39 void __init idle_thread_set_boot_cpu(void)
40 { 40 {
41 per_cpu(idle_threads, smp_processor_id 41 per_cpu(idle_threads, smp_processor_id()) = current;
42 } 42 }
43 43
44 /** 44 /**
45 * idle_init - Initialize the idle thread for 45 * idle_init - Initialize the idle thread for a cpu
46 * @cpu: The cpu for which the idle thr 46 * @cpu: The cpu for which the idle thread should be initialized
47 * 47 *
48 * Creates the thread if it does not exist. 48 * Creates the thread if it does not exist.
49 */ 49 */
50 static __always_inline void idle_init(unsigned 50 static __always_inline void idle_init(unsigned int cpu)
51 { 51 {
52 struct task_struct *tsk = per_cpu(idle 52 struct task_struct *tsk = per_cpu(idle_threads, cpu);
53 53
54 if (!tsk) { 54 if (!tsk) {
55 tsk = fork_idle(cpu); 55 tsk = fork_idle(cpu);
56 if (IS_ERR(tsk)) 56 if (IS_ERR(tsk))
57 pr_err("SMP: fork_idle 57 pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
58 else 58 else
59 per_cpu(idle_threads, 59 per_cpu(idle_threads, cpu) = tsk;
60 } 60 }
61 } 61 }
62 62
63 /** 63 /**
64 * idle_threads_init - Initialize idle threads 64 * idle_threads_init - Initialize idle threads for all cpus
65 */ 65 */
66 void __init idle_threads_init(void) 66 void __init idle_threads_init(void)
67 { 67 {
68 unsigned int cpu, boot_cpu; 68 unsigned int cpu, boot_cpu;
69 69
70 boot_cpu = smp_processor_id(); 70 boot_cpu = smp_processor_id();
71 71
72 for_each_possible_cpu(cpu) { 72 for_each_possible_cpu(cpu) {
73 if (cpu != boot_cpu) 73 if (cpu != boot_cpu)
74 idle_init(cpu); 74 idle_init(cpu);
75 } 75 }
76 } 76 }
77 #endif 77 #endif
78 78
79 #endif /* #ifdef CONFIG_SMP */ 79 #endif /* #ifdef CONFIG_SMP */
80 80
81 static LIST_HEAD(hotplug_threads); 81 static LIST_HEAD(hotplug_threads);
82 static DEFINE_MUTEX(smpboot_threads_lock); 82 static DEFINE_MUTEX(smpboot_threads_lock);
83 83
84 struct smpboot_thread_data { 84 struct smpboot_thread_data {
85 unsigned int cpu; 85 unsigned int cpu;
86 unsigned int status 86 unsigned int status;
87 struct smp_hotplug_thread *ht; 87 struct smp_hotplug_thread *ht;
88 }; 88 };
89 89
90 enum { 90 enum {
91 HP_THREAD_NONE = 0, 91 HP_THREAD_NONE = 0,
92 HP_THREAD_ACTIVE, 92 HP_THREAD_ACTIVE,
93 HP_THREAD_PARKED, 93 HP_THREAD_PARKED,
94 }; 94 };
95 95
96 /** 96 /**
97 * smpboot_thread_fn - percpu hotplug thread l 97 * smpboot_thread_fn - percpu hotplug thread loop function
98 * @data: thread data pointer 98 * @data: thread data pointer
99 * 99 *
100 * Checks for thread stop and park conditions. 100 * Checks for thread stop and park conditions. Calls the necessary
101 * setup, cleanup, park and unpark functions f 101 * setup, cleanup, park and unpark functions for the registered
102 * thread. 102 * thread.
103 * 103 *
104 * Returns 1 when the thread should exit, 0 ot 104 * Returns 1 when the thread should exit, 0 otherwise.
105 */ 105 */
106 static int smpboot_thread_fn(void *data) 106 static int smpboot_thread_fn(void *data)
107 { 107 {
108 struct smpboot_thread_data *td = data; 108 struct smpboot_thread_data *td = data;
109 struct smp_hotplug_thread *ht = td->ht 109 struct smp_hotplug_thread *ht = td->ht;
110 110
111 while (1) { 111 while (1) {
112 set_current_state(TASK_INTERRU 112 set_current_state(TASK_INTERRUPTIBLE);
113 preempt_disable(); 113 preempt_disable();
114 if (kthread_should_stop()) { 114 if (kthread_should_stop()) {
115 __set_current_state(TA 115 __set_current_state(TASK_RUNNING);
116 preempt_enable(); 116 preempt_enable();
117 /* cleanup must mirror 117 /* cleanup must mirror setup */
118 if (ht->cleanup && td- 118 if (ht->cleanup && td->status != HP_THREAD_NONE)
119 ht->cleanup(td 119 ht->cleanup(td->cpu, cpu_online(td->cpu));
120 kfree(td); 120 kfree(td);
121 return 0; 121 return 0;
122 } 122 }
123 123
124 if (kthread_should_park()) { 124 if (kthread_should_park()) {
125 __set_current_state(TA 125 __set_current_state(TASK_RUNNING);
126 preempt_enable(); 126 preempt_enable();
127 if (ht->park && td->st 127 if (ht->park && td->status == HP_THREAD_ACTIVE) {
128 BUG_ON(td->cpu 128 BUG_ON(td->cpu != smp_processor_id());
129 ht->park(td->c 129 ht->park(td->cpu);
130 td->status = H 130 td->status = HP_THREAD_PARKED;
131 } 131 }
132 kthread_parkme(); 132 kthread_parkme();
133 /* We might have been 133 /* We might have been woken for stop */
134 continue; 134 continue;
135 } 135 }
136 136
137 BUG_ON(td->cpu != smp_processo 137 BUG_ON(td->cpu != smp_processor_id());
138 138
139 /* Check for state change setu 139 /* Check for state change setup */
140 switch (td->status) { 140 switch (td->status) {
141 case HP_THREAD_NONE: 141 case HP_THREAD_NONE:
142 __set_current_state(TA 142 __set_current_state(TASK_RUNNING);
143 preempt_enable(); 143 preempt_enable();
144 if (ht->setup) 144 if (ht->setup)
145 ht->setup(td-> 145 ht->setup(td->cpu);
146 td->status = HP_THREAD 146 td->status = HP_THREAD_ACTIVE;
147 continue; 147 continue;
148 148
149 case HP_THREAD_PARKED: 149 case HP_THREAD_PARKED:
150 __set_current_state(TA 150 __set_current_state(TASK_RUNNING);
151 preempt_enable(); 151 preempt_enable();
152 if (ht->unpark) 152 if (ht->unpark)
153 ht->unpark(td- 153 ht->unpark(td->cpu);
154 td->status = HP_THREAD 154 td->status = HP_THREAD_ACTIVE;
155 continue; 155 continue;
156 } 156 }
157 157
158 if (!ht->thread_should_run(td- 158 if (!ht->thread_should_run(td->cpu)) {
159 preempt_enable_no_resc 159 preempt_enable_no_resched();
160 schedule(); 160 schedule();
161 } else { 161 } else {
162 __set_current_state(TA 162 __set_current_state(TASK_RUNNING);
163 preempt_enable(); 163 preempt_enable();
164 ht->thread_fn(td->cpu) 164 ht->thread_fn(td->cpu);
165 } 165 }
166 } 166 }
167 } 167 }
168 168
169 static int 169 static int
170 __smpboot_create_thread(struct smp_hotplug_thr 170 __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
171 { 171 {
172 struct task_struct *tsk = *per_cpu_ptr 172 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
173 struct smpboot_thread_data *td; 173 struct smpboot_thread_data *td;
174 174
175 if (tsk) 175 if (tsk)
176 return 0; 176 return 0;
177 177
178 td = kzalloc_node(sizeof(*td), GFP_KER 178 td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
179 if (!td) 179 if (!td)
180 return -ENOMEM; 180 return -ENOMEM;
181 td->cpu = cpu; 181 td->cpu = cpu;
182 td->ht = ht; 182 td->ht = ht;
183 183
184 tsk = kthread_create_on_cpu(smpboot_th 184 tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
185 ht->thread 185 ht->thread_comm);
186 if (IS_ERR(tsk)) { 186 if (IS_ERR(tsk)) {
187 kfree(td); 187 kfree(td);
188 return PTR_ERR(tsk); 188 return PTR_ERR(tsk);
189 } 189 }
190 kthread_set_per_cpu(tsk, cpu); 190 kthread_set_per_cpu(tsk, cpu);
191 /* 191 /*
192 * Park the thread so that it could st 192 * Park the thread so that it could start right on the CPU
193 * when it is available. 193 * when it is available.
194 */ 194 */
195 kthread_park(tsk); 195 kthread_park(tsk);
196 get_task_struct(tsk); 196 get_task_struct(tsk);
197 *per_cpu_ptr(ht->store, cpu) = tsk; 197 *per_cpu_ptr(ht->store, cpu) = tsk;
198 if (ht->create) { 198 if (ht->create) {
199 /* 199 /*
200 * Make sure that the task has 200 * Make sure that the task has actually scheduled out
201 * into park position, before 201 * into park position, before calling the create
202 * callback. At least the migr 202 * callback. At least the migration thread callback
203 * requires that the task is o 203 * requires that the task is off the runqueue.
204 */ 204 */
205 if (!wait_task_inactive(tsk, T 205 if (!wait_task_inactive(tsk, TASK_PARKED))
206 WARN_ON(1); 206 WARN_ON(1);
207 else 207 else
208 ht->create(cpu); 208 ht->create(cpu);
209 } 209 }
210 return 0; 210 return 0;
211 } 211 }
212 212
213 int smpboot_create_threads(unsigned int cpu) 213 int smpboot_create_threads(unsigned int cpu)
214 { 214 {
215 struct smp_hotplug_thread *cur; 215 struct smp_hotplug_thread *cur;
216 int ret = 0; 216 int ret = 0;
217 217
218 mutex_lock(&smpboot_threads_lock); 218 mutex_lock(&smpboot_threads_lock);
219 list_for_each_entry(cur, &hotplug_thre 219 list_for_each_entry(cur, &hotplug_threads, list) {
220 ret = __smpboot_create_thread( 220 ret = __smpboot_create_thread(cur, cpu);
221 if (ret) 221 if (ret)
222 break; 222 break;
223 } 223 }
224 mutex_unlock(&smpboot_threads_lock); 224 mutex_unlock(&smpboot_threads_lock);
225 return ret; 225 return ret;
226 } 226 }
227 227
228 static void smpboot_unpark_thread(struct smp_h 228 static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
229 { 229 {
230 struct task_struct *tsk = *per_cpu_ptr 230 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
231 231
232 if (!ht->selfparking) 232 if (!ht->selfparking)
233 kthread_unpark(tsk); 233 kthread_unpark(tsk);
234 } 234 }
235 235
236 int smpboot_unpark_threads(unsigned int cpu) 236 int smpboot_unpark_threads(unsigned int cpu)
237 { 237 {
238 struct smp_hotplug_thread *cur; 238 struct smp_hotplug_thread *cur;
239 239
240 mutex_lock(&smpboot_threads_lock); 240 mutex_lock(&smpboot_threads_lock);
241 list_for_each_entry(cur, &hotplug_thre 241 list_for_each_entry(cur, &hotplug_threads, list)
242 smpboot_unpark_thread(cur, cpu 242 smpboot_unpark_thread(cur, cpu);
243 mutex_unlock(&smpboot_threads_lock); 243 mutex_unlock(&smpboot_threads_lock);
244 return 0; 244 return 0;
245 } 245 }
246 246
247 static void smpboot_park_thread(struct smp_hot 247 static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
248 { 248 {
249 struct task_struct *tsk = *per_cpu_ptr 249 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
250 250
251 if (tsk && !ht->selfparking) 251 if (tsk && !ht->selfparking)
252 kthread_park(tsk); 252 kthread_park(tsk);
253 } 253 }
254 254
255 int smpboot_park_threads(unsigned int cpu) 255 int smpboot_park_threads(unsigned int cpu)
256 { 256 {
257 struct smp_hotplug_thread *cur; 257 struct smp_hotplug_thread *cur;
258 258
259 mutex_lock(&smpboot_threads_lock); 259 mutex_lock(&smpboot_threads_lock);
260 list_for_each_entry_reverse(cur, &hotp 260 list_for_each_entry_reverse(cur, &hotplug_threads, list)
261 smpboot_park_thread(cur, cpu); 261 smpboot_park_thread(cur, cpu);
262 mutex_unlock(&smpboot_threads_lock); 262 mutex_unlock(&smpboot_threads_lock);
263 return 0; 263 return 0;
264 } 264 }
265 265
266 static void smpboot_destroy_threads(struct smp 266 static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
267 { 267 {
268 unsigned int cpu; 268 unsigned int cpu;
269 269
270 /* We need to destroy also the parked 270 /* We need to destroy also the parked threads of offline cpus */
271 for_each_possible_cpu(cpu) { 271 for_each_possible_cpu(cpu) {
272 struct task_struct *tsk = *per 272 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
273 273
274 if (tsk) { 274 if (tsk) {
275 kthread_stop_put(tsk); !! 275 kthread_stop(tsk);
>> 276 put_task_struct(tsk);
276 *per_cpu_ptr(ht->store 277 *per_cpu_ptr(ht->store, cpu) = NULL;
277 } 278 }
278 } 279 }
279 } 280 }
280 281
281 /** 282 /**
282 * smpboot_register_percpu_thread - Register a 283 * smpboot_register_percpu_thread - Register a per_cpu thread related
283 * to 284 * to hotplug
284 * @plug_thread: Hotplug thread descrip 285 * @plug_thread: Hotplug thread descriptor
285 * 286 *
286 * Creates and starts the threads on all onlin 287 * Creates and starts the threads on all online cpus.
287 */ 288 */
288 int smpboot_register_percpu_thread(struct smp_ 289 int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
289 { 290 {
290 unsigned int cpu; 291 unsigned int cpu;
291 int ret = 0; 292 int ret = 0;
292 293
293 cpus_read_lock(); 294 cpus_read_lock();
294 mutex_lock(&smpboot_threads_lock); 295 mutex_lock(&smpboot_threads_lock);
295 for_each_online_cpu(cpu) { 296 for_each_online_cpu(cpu) {
296 ret = __smpboot_create_thread( 297 ret = __smpboot_create_thread(plug_thread, cpu);
297 if (ret) { 298 if (ret) {
298 smpboot_destroy_thread 299 smpboot_destroy_threads(plug_thread);
299 goto out; 300 goto out;
300 } 301 }
301 smpboot_unpark_thread(plug_thr 302 smpboot_unpark_thread(plug_thread, cpu);
302 } 303 }
303 list_add(&plug_thread->list, &hotplug_ 304 list_add(&plug_thread->list, &hotplug_threads);
304 out: 305 out:
305 mutex_unlock(&smpboot_threads_lock); 306 mutex_unlock(&smpboot_threads_lock);
306 cpus_read_unlock(); 307 cpus_read_unlock();
307 return ret; 308 return ret;
308 } 309 }
309 EXPORT_SYMBOL_GPL(smpboot_register_percpu_thre 310 EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
310 311
311 /** 312 /**
312 * smpboot_unregister_percpu_thread - Unregist 313 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
313 * @plug_thread: Hotplug thread descrip 314 * @plug_thread: Hotplug thread descriptor
314 * 315 *
315 * Stops all threads on all possible cpus. 316 * Stops all threads on all possible cpus.
316 */ 317 */
317 void smpboot_unregister_percpu_thread(struct s 318 void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
318 { 319 {
319 cpus_read_lock(); 320 cpus_read_lock();
320 mutex_lock(&smpboot_threads_lock); 321 mutex_lock(&smpboot_threads_lock);
321 list_del(&plug_thread->list); 322 list_del(&plug_thread->list);
322 smpboot_destroy_threads(plug_thread); 323 smpboot_destroy_threads(plug_thread);
323 mutex_unlock(&smpboot_threads_lock); 324 mutex_unlock(&smpboot_threads_lock);
324 cpus_read_unlock(); 325 cpus_read_unlock();
325 } 326 }
326 EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_th 327 EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
>> 328
>> 329 static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
>> 330
>> 331 /*
>> 332 * Called to poll specified CPU's state, for example, when waiting for
>> 333 * a CPU to come online.
>> 334 */
>> 335 int cpu_report_state(int cpu)
>> 336 {
>> 337 return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
>> 338 }
>> 339
>> 340 /*
>> 341 * If CPU has died properly, set its state to CPU_UP_PREPARE and
>> 342 * return success. Otherwise, return -EBUSY if the CPU died after
>> 343 * cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
>> 344 * if cpu_wait_death() timed out and the CPU still hasn't gotten around
>> 345 * to dying. In the latter two cases, the CPU might not be set up
>> 346 * properly, but it is up to the arch-specific code to decide.
>> 347 * Finally, -EIO indicates an unanticipated problem.
>> 348 *
>> 349 * Note that it is permissible to omit this call entirely, as is
>> 350 * done in architectures that do no CPU-hotplug error checking.
>> 351 */
>> 352 int cpu_check_up_prepare(int cpu)
>> 353 {
>> 354 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>> 355 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
>> 356 return 0;
>> 357 }
>> 358
>> 359 switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
>> 360
>> 361 case CPU_POST_DEAD:
>> 362
>> 363 /* The CPU died properly, so just start it up again. */
>> 364 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
>> 365 return 0;
>> 366
>> 367 case CPU_DEAD_FROZEN:
>> 368
>> 369 /*
>> 370 * Timeout during CPU death, so let caller know.
>> 371 * The outgoing CPU completed its processing, but after
>> 372 * cpu_wait_death() timed out and reported the error. The
>> 373 * caller is free to proceed, in which case the state
>> 374 * will be reset properly by cpu_set_state_online().
>> 375 * Proceeding despite this -EBUSY return makes sense
>> 376 * for systems where the outgoing CPUs take themselves
>> 377 * offline, with no post-death manipulation required from
>> 378 * a surviving CPU.
>> 379 */
>> 380 return -EBUSY;
>> 381
>> 382 case CPU_BROKEN:
>> 383
>> 384 /*
>> 385 * The most likely reason we got here is that there was
>> 386 * a timeout during CPU death, and the outgoing CPU never
>> 387 * did complete its processing. This could happen on
>> 388 * a virtualized system if the outgoing VCPU gets preempted
>> 389 * for more than five seconds, and the user attempts to
>> 390 * immediately online that same CPU. Trying again later
>> 391 * might return -EBUSY above, hence -EAGAIN.
>> 392 */
>> 393 return -EAGAIN;
>> 394
>> 395 default:
>> 396
>> 397 /* Should not happen. Famous last words. */
>> 398 return -EIO;
>> 399 }
>> 400 }
>> 401
>> 402 /*
>> 403 * Mark the specified CPU online.
>> 404 *
>> 405 * Note that it is permissible to omit this call entirely, as is
>> 406 * done in architectures that do no CPU-hotplug error checking.
>> 407 */
>> 408 void cpu_set_state_online(int cpu)
>> 409 {
>> 410 (void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
>> 411 }
>> 412
>> 413 #ifdef CONFIG_HOTPLUG_CPU
>> 414
>> 415 /*
>> 416 * Wait for the specified CPU to exit the idle loop and die.
>> 417 */
>> 418 bool cpu_wait_death(unsigned int cpu, int seconds)
>> 419 {
>> 420 int jf_left = seconds * HZ;
>> 421 int oldstate;
>> 422 bool ret = true;
>> 423 int sleep_jf = 1;
>> 424
>> 425 might_sleep();
>> 426
>> 427 /* The outgoing CPU will normally get done quite quickly. */
>> 428 if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
>> 429 goto update_state;
>> 430 udelay(5);
>> 431
>> 432 /* But if the outgoing CPU dawdles, wait increasingly long times. */
>> 433 while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
>> 434 schedule_timeout_uninterruptible(sleep_jf);
>> 435 jf_left -= sleep_jf;
>> 436 if (jf_left <= 0)
>> 437 break;
>> 438 sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
>> 439 }
>> 440 update_state:
>> 441 oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
>> 442 if (oldstate == CPU_DEAD) {
>> 443 /* Outgoing CPU died normally, update state. */
>> 444 smp_mb(); /* atomic_read() before update. */
>> 445 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
>> 446 } else {
>> 447 /* Outgoing CPU still hasn't died, set state accordingly. */
>> 448 if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
>> 449 oldstate, CPU_BROKEN) != oldstate)
>> 450 goto update_state;
>> 451 ret = false;
>> 452 }
>> 453 return ret;
>> 454 }
>> 455
>> 456 /*
>> 457 * Called by the outgoing CPU to report its successful death. Return
>> 458 * false if this report follows the surviving CPU's timing out.
>> 459 *
>> 460 * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
>> 461 * timed out. This approach allows architectures to omit calls to
>> 462 * cpu_check_up_prepare() and cpu_set_state_online() without defeating
>> 463 * the next cpu_wait_death()'s polling loop.
>> 464 */
>> 465 bool cpu_report_death(void)
>> 466 {
>> 467 int oldstate;
>> 468 int newstate;
>> 469 int cpu = smp_processor_id();
>> 470
>> 471 do {
>> 472 oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
>> 473 if (oldstate != CPU_BROKEN)
>> 474 newstate = CPU_DEAD;
>> 475 else
>> 476 newstate = CPU_DEAD_FROZEN;
>> 477 } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
>> 478 oldstate, newstate) != oldstate);
>> 479 return newstate == CPU_DEAD;
>> 480 }
>> 481
>> 482 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
327 483
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