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267f685b PB |
1 | /* |
2 | * CPU thread main loop - common bits for user and system mode emulation | |
3 | * | |
4 | * Copyright (c) 2003-2005 Fabrice Bellard | |
5 | * | |
6 | * This library is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU Lesser General Public | |
8 | * License as published by the Free Software Foundation; either | |
d6ea4236 | 9 | * version 2.1 of the License, or (at your option) any later version. |
267f685b PB |
10 | * |
11 | * This library is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * Lesser General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU Lesser General Public | |
17 | * License along with this library; if not, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | #include "qemu/osdep.h" | |
53f5ed95 | 21 | #include "qemu/main-loop.h" |
267f685b | 22 | #include "exec/cpu-common.h" |
2e5b09fd | 23 | #include "hw/core/cpu.h" |
267f685b | 24 | #include "sysemu/cpus.h" |
6e8a355d | 25 | #include "qemu/lockable.h" |
267f685b PB |
26 | |
27 | static QemuMutex qemu_cpu_list_lock; | |
ab129972 PB |
28 | static QemuCond exclusive_cond; |
29 | static QemuCond exclusive_resume; | |
d148d90e | 30 | static QemuCond qemu_work_cond; |
267f685b | 31 | |
c265e976 PB |
32 | /* >= 1 if a thread is inside start_exclusive/end_exclusive. Written |
33 | * under qemu_cpu_list_lock, read with atomic operations. | |
34 | */ | |
ab129972 PB |
35 | static int pending_cpus; |
36 | ||
267f685b PB |
37 | void qemu_init_cpu_list(void) |
38 | { | |
ab129972 PB |
39 | /* This is needed because qemu_init_cpu_list is also called by the |
40 | * child process in a fork. */ | |
41 | pending_cpus = 0; | |
42 | ||
267f685b | 43 | qemu_mutex_init(&qemu_cpu_list_lock); |
ab129972 PB |
44 | qemu_cond_init(&exclusive_cond); |
45 | qemu_cond_init(&exclusive_resume); | |
d148d90e | 46 | qemu_cond_init(&qemu_work_cond); |
267f685b PB |
47 | } |
48 | ||
49 | void cpu_list_lock(void) | |
50 | { | |
51 | qemu_mutex_lock(&qemu_cpu_list_lock); | |
52 | } | |
53 | ||
54 | void cpu_list_unlock(void) | |
55 | { | |
56 | qemu_mutex_unlock(&qemu_cpu_list_lock); | |
57 | } | |
58 | ||
59 | static bool cpu_index_auto_assigned; | |
60 | ||
61 | static int cpu_get_free_index(void) | |
62 | { | |
63 | CPUState *some_cpu; | |
716386e3 | 64 | int max_cpu_index = 0; |
267f685b PB |
65 | |
66 | cpu_index_auto_assigned = true; | |
67 | CPU_FOREACH(some_cpu) { | |
716386e3 AB |
68 | if (some_cpu->cpu_index >= max_cpu_index) { |
69 | max_cpu_index = some_cpu->cpu_index + 1; | |
70 | } | |
267f685b | 71 | } |
716386e3 | 72 | return max_cpu_index; |
267f685b PB |
73 | } |
74 | ||
421a75e2 PMD |
75 | CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus); |
76 | ||
267f685b PB |
77 | void cpu_list_add(CPUState *cpu) |
78 | { | |
6e8a355d | 79 | QEMU_LOCK_GUARD(&qemu_cpu_list_lock); |
267f685b PB |
80 | if (cpu->cpu_index == UNASSIGNED_CPU_INDEX) { |
81 | cpu->cpu_index = cpu_get_free_index(); | |
82 | assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX); | |
83 | } else { | |
84 | assert(!cpu_index_auto_assigned); | |
85 | } | |
068a5ea0 | 86 | QTAILQ_INSERT_TAIL_RCU(&cpus, cpu, node); |
267f685b PB |
87 | } |
88 | ||
89 | void cpu_list_remove(CPUState *cpu) | |
90 | { | |
6e8a355d | 91 | QEMU_LOCK_GUARD(&qemu_cpu_list_lock); |
267f685b PB |
92 | if (!QTAILQ_IN_USE(cpu, node)) { |
93 | /* there is nothing to undo since cpu_exec_init() hasn't been called */ | |
267f685b PB |
94 | return; |
95 | } | |
96 | ||
068a5ea0 | 97 | QTAILQ_REMOVE_RCU(&cpus, cpu, node); |
267f685b | 98 | cpu->cpu_index = UNASSIGNED_CPU_INDEX; |
267f685b | 99 | } |
d148d90e | 100 | |
421a75e2 PMD |
101 | CPUState *qemu_get_cpu(int index) |
102 | { | |
103 | CPUState *cpu; | |
104 | ||
105 | CPU_FOREACH(cpu) { | |
106 | if (cpu->cpu_index == index) { | |
107 | return cpu; | |
108 | } | |
109 | } | |
110 | ||
111 | return NULL; | |
112 | } | |
113 | ||
114 | /* current CPU in the current thread. It is only valid inside cpu_exec() */ | |
115 | __thread CPUState *current_cpu; | |
116 | ||
d148d90e | 117 | struct qemu_work_item { |
0c0fcc20 | 118 | QSIMPLEQ_ENTRY(qemu_work_item) node; |
d148d90e | 119 | run_on_cpu_func func; |
14e6fe12 | 120 | run_on_cpu_data data; |
53f5ed95 | 121 | bool free, exclusive, done; |
d148d90e SF |
122 | }; |
123 | ||
124 | static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi) | |
125 | { | |
126 | qemu_mutex_lock(&cpu->work_mutex); | |
0c0fcc20 | 127 | QSIMPLEQ_INSERT_TAIL(&cpu->work_list, wi, node); |
d148d90e SF |
128 | wi->done = false; |
129 | qemu_mutex_unlock(&cpu->work_mutex); | |
130 | ||
131 | qemu_cpu_kick(cpu); | |
132 | } | |
133 | ||
14e6fe12 | 134 | void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data, |
d148d90e SF |
135 | QemuMutex *mutex) |
136 | { | |
137 | struct qemu_work_item wi; | |
138 | ||
139 | if (qemu_cpu_is_self(cpu)) { | |
140 | func(cpu, data); | |
141 | return; | |
142 | } | |
143 | ||
144 | wi.func = func; | |
145 | wi.data = data; | |
0e55539c | 146 | wi.done = false; |
d148d90e | 147 | wi.free = false; |
53f5ed95 | 148 | wi.exclusive = false; |
d148d90e SF |
149 | |
150 | queue_work_on_cpu(cpu, &wi); | |
d73415a3 | 151 | while (!qatomic_mb_read(&wi.done)) { |
d148d90e SF |
152 | CPUState *self_cpu = current_cpu; |
153 | ||
154 | qemu_cond_wait(&qemu_work_cond, mutex); | |
155 | current_cpu = self_cpu; | |
156 | } | |
157 | } | |
158 | ||
14e6fe12 | 159 | void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data) |
d148d90e SF |
160 | { |
161 | struct qemu_work_item *wi; | |
162 | ||
d148d90e SF |
163 | wi = g_malloc0(sizeof(struct qemu_work_item)); |
164 | wi->func = func; | |
165 | wi->data = data; | |
166 | wi->free = true; | |
167 | ||
168 | queue_work_on_cpu(cpu, wi); | |
169 | } | |
170 | ||
ab129972 PB |
171 | /* Wait for pending exclusive operations to complete. The CPU list lock |
172 | must be held. */ | |
173 | static inline void exclusive_idle(void) | |
174 | { | |
175 | while (pending_cpus) { | |
176 | qemu_cond_wait(&exclusive_resume, &qemu_cpu_list_lock); | |
177 | } | |
178 | } | |
179 | ||
180 | /* Start an exclusive operation. | |
758e1b2b | 181 | Must only be called from outside cpu_exec. */ |
ab129972 PB |
182 | void start_exclusive(void) |
183 | { | |
184 | CPUState *other_cpu; | |
c265e976 | 185 | int running_cpus; |
ab129972 PB |
186 | |
187 | qemu_mutex_lock(&qemu_cpu_list_lock); | |
188 | exclusive_idle(); | |
189 | ||
190 | /* Make all other cpus stop executing. */ | |
d73415a3 | 191 | qatomic_set(&pending_cpus, 1); |
c265e976 PB |
192 | |
193 | /* Write pending_cpus before reading other_cpu->running. */ | |
194 | smp_mb(); | |
195 | running_cpus = 0; | |
ab129972 | 196 | CPU_FOREACH(other_cpu) { |
d73415a3 | 197 | if (qatomic_read(&other_cpu->running)) { |
c265e976 PB |
198 | other_cpu->has_waiter = true; |
199 | running_cpus++; | |
ab129972 PB |
200 | qemu_cpu_kick(other_cpu); |
201 | } | |
202 | } | |
c265e976 | 203 | |
d73415a3 | 204 | qatomic_set(&pending_cpus, running_cpus + 1); |
ab129972 PB |
205 | while (pending_cpus > 1) { |
206 | qemu_cond_wait(&exclusive_cond, &qemu_cpu_list_lock); | |
207 | } | |
758e1b2b PB |
208 | |
209 | /* Can release mutex, no one will enter another exclusive | |
210 | * section until end_exclusive resets pending_cpus to 0. | |
211 | */ | |
212 | qemu_mutex_unlock(&qemu_cpu_list_lock); | |
cfbc3c60 EC |
213 | |
214 | current_cpu->in_exclusive_context = true; | |
ab129972 PB |
215 | } |
216 | ||
758e1b2b | 217 | /* Finish an exclusive operation. */ |
ab129972 PB |
218 | void end_exclusive(void) |
219 | { | |
cfbc3c60 EC |
220 | current_cpu->in_exclusive_context = false; |
221 | ||
758e1b2b | 222 | qemu_mutex_lock(&qemu_cpu_list_lock); |
d73415a3 | 223 | qatomic_set(&pending_cpus, 0); |
ab129972 PB |
224 | qemu_cond_broadcast(&exclusive_resume); |
225 | qemu_mutex_unlock(&qemu_cpu_list_lock); | |
226 | } | |
227 | ||
228 | /* Wait for exclusive ops to finish, and begin cpu execution. */ | |
229 | void cpu_exec_start(CPUState *cpu) | |
230 | { | |
d73415a3 | 231 | qatomic_set(&cpu->running, true); |
c265e976 PB |
232 | |
233 | /* Write cpu->running before reading pending_cpus. */ | |
234 | smp_mb(); | |
235 | ||
236 | /* 1. start_exclusive saw cpu->running == true and pending_cpus >= 1. | |
237 | * After taking the lock we'll see cpu->has_waiter == true and run---not | |
238 | * for long because start_exclusive kicked us. cpu_exec_end will | |
239 | * decrement pending_cpus and signal the waiter. | |
240 | * | |
241 | * 2. start_exclusive saw cpu->running == false but pending_cpus >= 1. | |
242 | * This includes the case when an exclusive item is running now. | |
243 | * Then we'll see cpu->has_waiter == false and wait for the item to | |
244 | * complete. | |
245 | * | |
246 | * 3. pending_cpus == 0. Then start_exclusive is definitely going to | |
247 | * see cpu->running == true, and it will kick the CPU. | |
248 | */ | |
d73415a3 | 249 | if (unlikely(qatomic_read(&pending_cpus))) { |
6e8a355d | 250 | QEMU_LOCK_GUARD(&qemu_cpu_list_lock); |
c265e976 PB |
251 | if (!cpu->has_waiter) { |
252 | /* Not counted in pending_cpus, let the exclusive item | |
253 | * run. Since we have the lock, just set cpu->running to true | |
254 | * while holding it; no need to check pending_cpus again. | |
255 | */ | |
d73415a3 | 256 | qatomic_set(&cpu->running, false); |
c265e976 PB |
257 | exclusive_idle(); |
258 | /* Now pending_cpus is zero. */ | |
d73415a3 | 259 | qatomic_set(&cpu->running, true); |
c265e976 PB |
260 | } else { |
261 | /* Counted in pending_cpus, go ahead and release the | |
262 | * waiter at cpu_exec_end. | |
263 | */ | |
264 | } | |
c265e976 | 265 | } |
ab129972 PB |
266 | } |
267 | ||
268 | /* Mark cpu as not executing, and release pending exclusive ops. */ | |
269 | void cpu_exec_end(CPUState *cpu) | |
270 | { | |
d73415a3 | 271 | qatomic_set(&cpu->running, false); |
c265e976 PB |
272 | |
273 | /* Write cpu->running before reading pending_cpus. */ | |
274 | smp_mb(); | |
275 | ||
276 | /* 1. start_exclusive saw cpu->running == true. Then it will increment | |
277 | * pending_cpus and wait for exclusive_cond. After taking the lock | |
278 | * we'll see cpu->has_waiter == true. | |
279 | * | |
280 | * 2. start_exclusive saw cpu->running == false but here pending_cpus >= 1. | |
281 | * This includes the case when an exclusive item started after setting | |
282 | * cpu->running to false and before we read pending_cpus. Then we'll see | |
283 | * cpu->has_waiter == false and not touch pending_cpus. The next call to | |
284 | * cpu_exec_start will run exclusive_idle if still necessary, thus waiting | |
285 | * for the item to complete. | |
286 | * | |
287 | * 3. pending_cpus == 0. Then start_exclusive is definitely going to | |
288 | * see cpu->running == false, and it can ignore this CPU until the | |
289 | * next cpu_exec_start. | |
290 | */ | |
d73415a3 | 291 | if (unlikely(qatomic_read(&pending_cpus))) { |
6e8a355d | 292 | QEMU_LOCK_GUARD(&qemu_cpu_list_lock); |
c265e976 PB |
293 | if (cpu->has_waiter) { |
294 | cpu->has_waiter = false; | |
d73415a3 | 295 | qatomic_set(&pending_cpus, pending_cpus - 1); |
c265e976 PB |
296 | if (pending_cpus == 1) { |
297 | qemu_cond_signal(&exclusive_cond); | |
298 | } | |
ab129972 PB |
299 | } |
300 | } | |
ab129972 PB |
301 | } |
302 | ||
14e6fe12 PB |
303 | void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, |
304 | run_on_cpu_data data) | |
53f5ed95 PB |
305 | { |
306 | struct qemu_work_item *wi; | |
307 | ||
308 | wi = g_malloc0(sizeof(struct qemu_work_item)); | |
309 | wi->func = func; | |
310 | wi->data = data; | |
311 | wi->free = true; | |
312 | wi->exclusive = true; | |
313 | ||
314 | queue_work_on_cpu(cpu, wi); | |
315 | } | |
316 | ||
d148d90e SF |
317 | void process_queued_cpu_work(CPUState *cpu) |
318 | { | |
319 | struct qemu_work_item *wi; | |
320 | ||
0c0fcc20 EC |
321 | qemu_mutex_lock(&cpu->work_mutex); |
322 | if (QSIMPLEQ_EMPTY(&cpu->work_list)) { | |
323 | qemu_mutex_unlock(&cpu->work_mutex); | |
d148d90e SF |
324 | return; |
325 | } | |
0c0fcc20 EC |
326 | while (!QSIMPLEQ_EMPTY(&cpu->work_list)) { |
327 | wi = QSIMPLEQ_FIRST(&cpu->work_list); | |
328 | QSIMPLEQ_REMOVE_HEAD(&cpu->work_list, node); | |
d148d90e | 329 | qemu_mutex_unlock(&cpu->work_mutex); |
53f5ed95 PB |
330 | if (wi->exclusive) { |
331 | /* Running work items outside the BQL avoids the following deadlock: | |
332 | * 1) start_exclusive() is called with the BQL taken while another | |
333 | * CPU is running; 2) cpu_exec in the other CPU tries to takes the | |
334 | * BQL, so it goes to sleep; start_exclusive() is sleeping too, so | |
335 | * neither CPU can proceed. | |
336 | */ | |
337 | qemu_mutex_unlock_iothread(); | |
338 | start_exclusive(); | |
339 | wi->func(cpu, wi->data); | |
340 | end_exclusive(); | |
341 | qemu_mutex_lock_iothread(); | |
342 | } else { | |
343 | wi->func(cpu, wi->data); | |
344 | } | |
d148d90e SF |
345 | qemu_mutex_lock(&cpu->work_mutex); |
346 | if (wi->free) { | |
347 | g_free(wi); | |
348 | } else { | |
d73415a3 | 349 | qatomic_mb_set(&wi->done, true); |
d148d90e SF |
350 | } |
351 | } | |
352 | qemu_mutex_unlock(&cpu->work_mutex); | |
353 | qemu_cond_broadcast(&qemu_work_cond); | |
354 | } |