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1 | /* | |
2 | * QEMU System Emulator | |
3 | * | |
4 | * Copyright (c) 2003-2008 Fabrice Bellard | |
5 | * | |
6 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
7 | * of this software and associated documentation files (the "Software"), to deal | |
8 | * in the Software without restriction, including without limitation the rights | |
9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
10 | * copies of the Software, and to permit persons to whom the Software is | |
11 | * furnished to do so, subject to the following conditions: | |
12 | * | |
13 | * The above copyright notice and this permission notice shall be included in | |
14 | * all copies or substantial portions of the Software. | |
15 | * | |
16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
19 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
22 | * THE SOFTWARE. | |
23 | */ | |
24 | ||
25 | #include "qemu/osdep.h" | |
26 | #include "qapi/error.h" | |
27 | #include "qemu-common.h" | |
28 | #include "block/aio.h" | |
29 | #include "block/thread-pool.h" | |
30 | #include "qemu/main-loop.h" | |
31 | #include "qemu/atomic.h" | |
32 | #include "block/raw-aio.h" | |
33 | ||
34 | /***********************************************************/ | |
35 | /* bottom halves (can be seen as timers which expire ASAP) */ | |
36 | ||
37 | struct QEMUBH { | |
38 | AioContext *ctx; | |
39 | QEMUBHFunc *cb; | |
40 | void *opaque; | |
41 | QEMUBH *next; | |
42 | bool scheduled; | |
43 | bool idle; | |
44 | bool deleted; | |
45 | }; | |
46 | ||
47 | QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque) | |
48 | { | |
49 | QEMUBH *bh; | |
50 | bh = g_new(QEMUBH, 1); | |
51 | *bh = (QEMUBH){ | |
52 | .ctx = ctx, | |
53 | .cb = cb, | |
54 | .opaque = opaque, | |
55 | }; | |
56 | qemu_mutex_lock(&ctx->bh_lock); | |
57 | bh->next = ctx->first_bh; | |
58 | /* Make sure that the members are ready before putting bh into list */ | |
59 | smp_wmb(); | |
60 | ctx->first_bh = bh; | |
61 | qemu_mutex_unlock(&ctx->bh_lock); | |
62 | return bh; | |
63 | } | |
64 | ||
65 | void aio_bh_call(QEMUBH *bh) | |
66 | { | |
67 | bh->cb(bh->opaque); | |
68 | } | |
69 | ||
70 | /* Multiple occurrences of aio_bh_poll cannot be called concurrently */ | |
71 | int aio_bh_poll(AioContext *ctx) | |
72 | { | |
73 | QEMUBH *bh, **bhp, *next; | |
74 | int ret; | |
75 | ||
76 | ctx->walking_bh++; | |
77 | ||
78 | ret = 0; | |
79 | for (bh = ctx->first_bh; bh; bh = next) { | |
80 | /* Make sure that fetching bh happens before accessing its members */ | |
81 | smp_read_barrier_depends(); | |
82 | next = bh->next; | |
83 | /* The atomic_xchg is paired with the one in qemu_bh_schedule. The | |
84 | * implicit memory barrier ensures that the callback sees all writes | |
85 | * done by the scheduling thread. It also ensures that the scheduling | |
86 | * thread sees the zero before bh->cb has run, and thus will call | |
87 | * aio_notify again if necessary. | |
88 | */ | |
89 | if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) { | |
90 | /* Idle BHs and the notify BH don't count as progress */ | |
91 | if (!bh->idle && bh != ctx->notify_dummy_bh) { | |
92 | ret = 1; | |
93 | } | |
94 | bh->idle = 0; | |
95 | aio_bh_call(bh); | |
96 | } | |
97 | } | |
98 | ||
99 | ctx->walking_bh--; | |
100 | ||
101 | /* remove deleted bhs */ | |
102 | if (!ctx->walking_bh) { | |
103 | qemu_mutex_lock(&ctx->bh_lock); | |
104 | bhp = &ctx->first_bh; | |
105 | while (*bhp) { | |
106 | bh = *bhp; | |
107 | if (bh->deleted) { | |
108 | *bhp = bh->next; | |
109 | g_free(bh); | |
110 | } else { | |
111 | bhp = &bh->next; | |
112 | } | |
113 | } | |
114 | qemu_mutex_unlock(&ctx->bh_lock); | |
115 | } | |
116 | ||
117 | return ret; | |
118 | } | |
119 | ||
120 | void qemu_bh_schedule_idle(QEMUBH *bh) | |
121 | { | |
122 | bh->idle = 1; | |
123 | /* Make sure that idle & any writes needed by the callback are done | |
124 | * before the locations are read in the aio_bh_poll. | |
125 | */ | |
126 | atomic_mb_set(&bh->scheduled, 1); | |
127 | } | |
128 | ||
129 | void qemu_bh_schedule(QEMUBH *bh) | |
130 | { | |
131 | AioContext *ctx; | |
132 | ||
133 | ctx = bh->ctx; | |
134 | bh->idle = 0; | |
135 | /* The memory barrier implicit in atomic_xchg makes sure that: | |
136 | * 1. idle & any writes needed by the callback are done before the | |
137 | * locations are read in the aio_bh_poll. | |
138 | * 2. ctx is loaded before scheduled is set and the callback has a chance | |
139 | * to execute. | |
140 | */ | |
141 | if (atomic_xchg(&bh->scheduled, 1) == 0) { | |
142 | aio_notify(ctx); | |
143 | } | |
144 | } | |
145 | ||
146 | ||
147 | /* This func is async. | |
148 | */ | |
149 | void qemu_bh_cancel(QEMUBH *bh) | |
150 | { | |
151 | bh->scheduled = 0; | |
152 | } | |
153 | ||
154 | /* This func is async.The bottom half will do the delete action at the finial | |
155 | * end. | |
156 | */ | |
157 | void qemu_bh_delete(QEMUBH *bh) | |
158 | { | |
159 | bh->scheduled = 0; | |
160 | bh->deleted = 1; | |
161 | } | |
162 | ||
163 | int64_t | |
164 | aio_compute_timeout(AioContext *ctx) | |
165 | { | |
166 | int64_t deadline; | |
167 | int timeout = -1; | |
168 | QEMUBH *bh; | |
169 | ||
170 | for (bh = ctx->first_bh; bh; bh = bh->next) { | |
171 | if (!bh->deleted && bh->scheduled) { | |
172 | if (bh->idle) { | |
173 | /* idle bottom halves will be polled at least | |
174 | * every 10ms */ | |
175 | timeout = 10000000; | |
176 | } else { | |
177 | /* non-idle bottom halves will be executed | |
178 | * immediately */ | |
179 | return 0; | |
180 | } | |
181 | } | |
182 | } | |
183 | ||
184 | deadline = timerlistgroup_deadline_ns(&ctx->tlg); | |
185 | if (deadline == 0) { | |
186 | return 0; | |
187 | } else { | |
188 | return qemu_soonest_timeout(timeout, deadline); | |
189 | } | |
190 | } | |
191 | ||
192 | static gboolean | |
193 | aio_ctx_prepare(GSource *source, gint *timeout) | |
194 | { | |
195 | AioContext *ctx = (AioContext *) source; | |
196 | ||
197 | atomic_or(&ctx->notify_me, 1); | |
198 | ||
199 | /* We assume there is no timeout already supplied */ | |
200 | *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)); | |
201 | ||
202 | if (aio_prepare(ctx)) { | |
203 | *timeout = 0; | |
204 | } | |
205 | ||
206 | return *timeout == 0; | |
207 | } | |
208 | ||
209 | static gboolean | |
210 | aio_ctx_check(GSource *source) | |
211 | { | |
212 | AioContext *ctx = (AioContext *) source; | |
213 | QEMUBH *bh; | |
214 | ||
215 | atomic_and(&ctx->notify_me, ~1); | |
216 | aio_notify_accept(ctx); | |
217 | ||
218 | for (bh = ctx->first_bh; bh; bh = bh->next) { | |
219 | if (!bh->deleted && bh->scheduled) { | |
220 | return true; | |
221 | } | |
222 | } | |
223 | return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0); | |
224 | } | |
225 | ||
226 | static gboolean | |
227 | aio_ctx_dispatch(GSource *source, | |
228 | GSourceFunc callback, | |
229 | gpointer user_data) | |
230 | { | |
231 | AioContext *ctx = (AioContext *) source; | |
232 | ||
233 | assert(callback == NULL); | |
234 | aio_dispatch(ctx); | |
235 | return true; | |
236 | } | |
237 | ||
238 | static void | |
239 | aio_ctx_finalize(GSource *source) | |
240 | { | |
241 | AioContext *ctx = (AioContext *) source; | |
242 | ||
243 | qemu_bh_delete(ctx->notify_dummy_bh); | |
244 | thread_pool_free(ctx->thread_pool); | |
245 | ||
246 | #ifdef CONFIG_LINUX_AIO | |
247 | if (ctx->linux_aio) { | |
248 | laio_detach_aio_context(ctx->linux_aio, ctx); | |
249 | laio_cleanup(ctx->linux_aio); | |
250 | ctx->linux_aio = NULL; | |
251 | } | |
252 | #endif | |
253 | ||
254 | qemu_mutex_lock(&ctx->bh_lock); | |
255 | while (ctx->first_bh) { | |
256 | QEMUBH *next = ctx->first_bh->next; | |
257 | ||
258 | /* qemu_bh_delete() must have been called on BHs in this AioContext */ | |
259 | assert(ctx->first_bh->deleted); | |
260 | ||
261 | g_free(ctx->first_bh); | |
262 | ctx->first_bh = next; | |
263 | } | |
264 | qemu_mutex_unlock(&ctx->bh_lock); | |
265 | ||
266 | aio_set_event_notifier(ctx, &ctx->notifier, false, NULL); | |
267 | event_notifier_cleanup(&ctx->notifier); | |
268 | rfifolock_destroy(&ctx->lock); | |
269 | qemu_mutex_destroy(&ctx->bh_lock); | |
270 | timerlistgroup_deinit(&ctx->tlg); | |
271 | } | |
272 | ||
273 | static GSourceFuncs aio_source_funcs = { | |
274 | aio_ctx_prepare, | |
275 | aio_ctx_check, | |
276 | aio_ctx_dispatch, | |
277 | aio_ctx_finalize | |
278 | }; | |
279 | ||
280 | GSource *aio_get_g_source(AioContext *ctx) | |
281 | { | |
282 | g_source_ref(&ctx->source); | |
283 | return &ctx->source; | |
284 | } | |
285 | ||
286 | ThreadPool *aio_get_thread_pool(AioContext *ctx) | |
287 | { | |
288 | if (!ctx->thread_pool) { | |
289 | ctx->thread_pool = thread_pool_new(ctx); | |
290 | } | |
291 | return ctx->thread_pool; | |
292 | } | |
293 | ||
294 | #ifdef CONFIG_LINUX_AIO | |
295 | LinuxAioState *aio_get_linux_aio(AioContext *ctx) | |
296 | { | |
297 | if (!ctx->linux_aio) { | |
298 | ctx->linux_aio = laio_init(); | |
299 | laio_attach_aio_context(ctx->linux_aio, ctx); | |
300 | } | |
301 | return ctx->linux_aio; | |
302 | } | |
303 | #endif | |
304 | ||
305 | void aio_notify(AioContext *ctx) | |
306 | { | |
307 | /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs | |
308 | * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll. | |
309 | */ | |
310 | smp_mb(); | |
311 | if (ctx->notify_me) { | |
312 | event_notifier_set(&ctx->notifier); | |
313 | atomic_mb_set(&ctx->notified, true); | |
314 | } | |
315 | } | |
316 | ||
317 | void aio_notify_accept(AioContext *ctx) | |
318 | { | |
319 | if (atomic_xchg(&ctx->notified, false)) { | |
320 | event_notifier_test_and_clear(&ctx->notifier); | |
321 | } | |
322 | } | |
323 | ||
324 | static void aio_timerlist_notify(void *opaque) | |
325 | { | |
326 | aio_notify(opaque); | |
327 | } | |
328 | ||
329 | static void aio_rfifolock_cb(void *opaque) | |
330 | { | |
331 | AioContext *ctx = opaque; | |
332 | ||
333 | /* Kick owner thread in case they are blocked in aio_poll() */ | |
334 | qemu_bh_schedule(ctx->notify_dummy_bh); | |
335 | } | |
336 | ||
337 | static void notify_dummy_bh(void *opaque) | |
338 | { | |
339 | /* Do nothing, we were invoked just to force the event loop to iterate */ | |
340 | } | |
341 | ||
342 | static void event_notifier_dummy_cb(EventNotifier *e) | |
343 | { | |
344 | } | |
345 | ||
346 | AioContext *aio_context_new(Error **errp) | |
347 | { | |
348 | int ret; | |
349 | AioContext *ctx; | |
350 | ||
351 | ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext)); | |
352 | aio_context_setup(ctx); | |
353 | ||
354 | ret = event_notifier_init(&ctx->notifier, false); | |
355 | if (ret < 0) { | |
356 | error_setg_errno(errp, -ret, "Failed to initialize event notifier"); | |
357 | goto fail; | |
358 | } | |
359 | g_source_set_can_recurse(&ctx->source, true); | |
360 | aio_set_event_notifier(ctx, &ctx->notifier, | |
361 | false, | |
362 | (EventNotifierHandler *) | |
363 | event_notifier_dummy_cb); | |
364 | #ifdef CONFIG_LINUX_AIO | |
365 | ctx->linux_aio = NULL; | |
366 | #endif | |
367 | ctx->thread_pool = NULL; | |
368 | qemu_mutex_init(&ctx->bh_lock); | |
369 | rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx); | |
370 | timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx); | |
371 | ||
372 | ctx->notify_dummy_bh = aio_bh_new(ctx, notify_dummy_bh, NULL); | |
373 | ||
374 | return ctx; | |
375 | fail: | |
376 | g_source_destroy(&ctx->source); | |
377 | return NULL; | |
378 | } | |
379 | ||
380 | void aio_context_ref(AioContext *ctx) | |
381 | { | |
382 | g_source_ref(&ctx->source); | |
383 | } | |
384 | ||
385 | void aio_context_unref(AioContext *ctx) | |
386 | { | |
387 | g_source_unref(&ctx->source); | |
388 | } | |
389 | ||
390 | void aio_context_acquire(AioContext *ctx) | |
391 | { | |
392 | rfifolock_lock(&ctx->lock); | |
393 | } | |
394 | ||
395 | void aio_context_release(AioContext *ctx) | |
396 | { | |
397 | rfifolock_unlock(&ctx->lock); | |
398 | } |