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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-common.h" | |
26 | #include "block/aio.h" | |
27 | #include "block/thread-pool.h" | |
28 | #include "qemu/main-loop.h" | |
29 | #include "qemu/atomic.h" | |
30 | ||
31 | /***********************************************************/ | |
32 | /* bottom halves (can be seen as timers which expire ASAP) */ | |
33 | ||
34 | struct QEMUBH { | |
35 | AioContext *ctx; | |
36 | QEMUBHFunc *cb; | |
37 | void *opaque; | |
38 | QEMUBH *next; | |
39 | bool scheduled; | |
40 | bool idle; | |
41 | bool deleted; | |
42 | }; | |
43 | ||
44 | QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque) | |
45 | { | |
46 | QEMUBH *bh; | |
47 | bh = g_new(QEMUBH, 1); | |
48 | *bh = (QEMUBH){ | |
49 | .ctx = ctx, | |
50 | .cb = cb, | |
51 | .opaque = opaque, | |
52 | }; | |
53 | qemu_mutex_lock(&ctx->bh_lock); | |
54 | bh->next = ctx->first_bh; | |
55 | /* Make sure that the members are ready before putting bh into list */ | |
56 | smp_wmb(); | |
57 | ctx->first_bh = bh; | |
58 | qemu_mutex_unlock(&ctx->bh_lock); | |
59 | return bh; | |
60 | } | |
61 | ||
62 | /* Multiple occurrences of aio_bh_poll cannot be called concurrently */ | |
63 | int aio_bh_poll(AioContext *ctx) | |
64 | { | |
65 | QEMUBH *bh, **bhp, *next; | |
66 | int ret; | |
67 | ||
68 | ctx->walking_bh++; | |
69 | ||
70 | ret = 0; | |
71 | for (bh = ctx->first_bh; bh; bh = next) { | |
72 | /* Make sure that fetching bh happens before accessing its members */ | |
73 | smp_read_barrier_depends(); | |
74 | next = bh->next; | |
75 | /* The atomic_xchg is paired with the one in qemu_bh_schedule. The | |
76 | * implicit memory barrier ensures that the callback sees all writes | |
77 | * done by the scheduling thread. It also ensures that the scheduling | |
78 | * thread sees the zero before bh->cb has run, and thus will call | |
79 | * aio_notify again if necessary. | |
80 | */ | |
81 | if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) { | |
82 | if (!bh->idle) | |
83 | ret = 1; | |
84 | bh->idle = 0; | |
85 | bh->cb(bh->opaque); | |
86 | } | |
87 | } | |
88 | ||
89 | ctx->walking_bh--; | |
90 | ||
91 | /* remove deleted bhs */ | |
92 | if (!ctx->walking_bh) { | |
93 | qemu_mutex_lock(&ctx->bh_lock); | |
94 | bhp = &ctx->first_bh; | |
95 | while (*bhp) { | |
96 | bh = *bhp; | |
97 | if (bh->deleted) { | |
98 | *bhp = bh->next; | |
99 | g_free(bh); | |
100 | } else { | |
101 | bhp = &bh->next; | |
102 | } | |
103 | } | |
104 | qemu_mutex_unlock(&ctx->bh_lock); | |
105 | } | |
106 | ||
107 | return ret; | |
108 | } | |
109 | ||
110 | void qemu_bh_schedule_idle(QEMUBH *bh) | |
111 | { | |
112 | bh->idle = 1; | |
113 | /* Make sure that idle & any writes needed by the callback are done | |
114 | * before the locations are read in the aio_bh_poll. | |
115 | */ | |
116 | atomic_mb_set(&bh->scheduled, 1); | |
117 | } | |
118 | ||
119 | void qemu_bh_schedule(QEMUBH *bh) | |
120 | { | |
121 | AioContext *ctx; | |
122 | ||
123 | ctx = bh->ctx; | |
124 | bh->idle = 0; | |
125 | /* The memory barrier implicit in atomic_xchg makes sure that: | |
126 | * 1. idle & any writes needed by the callback are done before the | |
127 | * locations are read in the aio_bh_poll. | |
128 | * 2. ctx is loaded before scheduled is set and the callback has a chance | |
129 | * to execute. | |
130 | */ | |
131 | if (atomic_xchg(&bh->scheduled, 1) == 0) { | |
132 | aio_notify(ctx); | |
133 | } | |
134 | } | |
135 | ||
136 | ||
137 | /* This func is async. | |
138 | */ | |
139 | void qemu_bh_cancel(QEMUBH *bh) | |
140 | { | |
141 | bh->scheduled = 0; | |
142 | } | |
143 | ||
144 | /* This func is async.The bottom half will do the delete action at the finial | |
145 | * end. | |
146 | */ | |
147 | void qemu_bh_delete(QEMUBH *bh) | |
148 | { | |
149 | bh->scheduled = 0; | |
150 | bh->deleted = 1; | |
151 | } | |
152 | ||
153 | int64_t | |
154 | aio_compute_timeout(AioContext *ctx) | |
155 | { | |
156 | int64_t deadline; | |
157 | int timeout = -1; | |
158 | QEMUBH *bh; | |
159 | ||
160 | for (bh = ctx->first_bh; bh; bh = bh->next) { | |
161 | if (!bh->deleted && bh->scheduled) { | |
162 | if (bh->idle) { | |
163 | /* idle bottom halves will be polled at least | |
164 | * every 10ms */ | |
165 | timeout = 10000000; | |
166 | } else { | |
167 | /* non-idle bottom halves will be executed | |
168 | * immediately */ | |
169 | return 0; | |
170 | } | |
171 | } | |
172 | } | |
173 | ||
174 | deadline = timerlistgroup_deadline_ns(&ctx->tlg); | |
175 | if (deadline == 0) { | |
176 | return 0; | |
177 | } else { | |
178 | return qemu_soonest_timeout(timeout, deadline); | |
179 | } | |
180 | } | |
181 | ||
182 | static gboolean | |
183 | aio_ctx_prepare(GSource *source, gint *timeout) | |
184 | { | |
185 | AioContext *ctx = (AioContext *) source; | |
186 | ||
187 | atomic_or(&ctx->notify_me, 1); | |
188 | ||
189 | /* We assume there is no timeout already supplied */ | |
190 | *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)); | |
191 | ||
192 | if (aio_prepare(ctx)) { | |
193 | *timeout = 0; | |
194 | } | |
195 | ||
196 | return *timeout == 0; | |
197 | } | |
198 | ||
199 | static gboolean | |
200 | aio_ctx_check(GSource *source) | |
201 | { | |
202 | AioContext *ctx = (AioContext *) source; | |
203 | QEMUBH *bh; | |
204 | ||
205 | atomic_and(&ctx->notify_me, ~1); | |
206 | aio_notify_accept(ctx); | |
207 | ||
208 | for (bh = ctx->first_bh; bh; bh = bh->next) { | |
209 | if (!bh->deleted && bh->scheduled) { | |
210 | return true; | |
211 | } | |
212 | } | |
213 | return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0); | |
214 | } | |
215 | ||
216 | static gboolean | |
217 | aio_ctx_dispatch(GSource *source, | |
218 | GSourceFunc callback, | |
219 | gpointer user_data) | |
220 | { | |
221 | AioContext *ctx = (AioContext *) source; | |
222 | ||
223 | assert(callback == NULL); | |
224 | aio_dispatch(ctx); | |
225 | return true; | |
226 | } | |
227 | ||
228 | static void | |
229 | aio_ctx_finalize(GSource *source) | |
230 | { | |
231 | AioContext *ctx = (AioContext *) source; | |
232 | ||
233 | thread_pool_free(ctx->thread_pool); | |
234 | ||
235 | qemu_mutex_lock(&ctx->bh_lock); | |
236 | while (ctx->first_bh) { | |
237 | QEMUBH *next = ctx->first_bh->next; | |
238 | ||
239 | /* qemu_bh_delete() must have been called on BHs in this AioContext */ | |
240 | assert(ctx->first_bh->deleted); | |
241 | ||
242 | g_free(ctx->first_bh); | |
243 | ctx->first_bh = next; | |
244 | } | |
245 | qemu_mutex_unlock(&ctx->bh_lock); | |
246 | ||
247 | aio_set_event_notifier(ctx, &ctx->notifier, NULL); | |
248 | event_notifier_cleanup(&ctx->notifier); | |
249 | rfifolock_destroy(&ctx->lock); | |
250 | qemu_mutex_destroy(&ctx->bh_lock); | |
251 | timerlistgroup_deinit(&ctx->tlg); | |
252 | } | |
253 | ||
254 | static GSourceFuncs aio_source_funcs = { | |
255 | aio_ctx_prepare, | |
256 | aio_ctx_check, | |
257 | aio_ctx_dispatch, | |
258 | aio_ctx_finalize | |
259 | }; | |
260 | ||
261 | GSource *aio_get_g_source(AioContext *ctx) | |
262 | { | |
263 | g_source_ref(&ctx->source); | |
264 | return &ctx->source; | |
265 | } | |
266 | ||
267 | ThreadPool *aio_get_thread_pool(AioContext *ctx) | |
268 | { | |
269 | if (!ctx->thread_pool) { | |
270 | ctx->thread_pool = thread_pool_new(ctx); | |
271 | } | |
272 | return ctx->thread_pool; | |
273 | } | |
274 | ||
275 | void aio_notify(AioContext *ctx) | |
276 | { | |
277 | /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs | |
278 | * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll. | |
279 | */ | |
280 | smp_mb(); | |
281 | if (ctx->notify_me) { | |
282 | event_notifier_set(&ctx->notifier); | |
283 | atomic_mb_set(&ctx->notified, true); | |
284 | } | |
285 | } | |
286 | ||
287 | void aio_notify_accept(AioContext *ctx) | |
288 | { | |
289 | if (atomic_xchg(&ctx->notified, false)) { | |
290 | event_notifier_test_and_clear(&ctx->notifier); | |
291 | } | |
292 | } | |
293 | ||
294 | static void aio_timerlist_notify(void *opaque) | |
295 | { | |
296 | aio_notify(opaque); | |
297 | } | |
298 | ||
299 | static void aio_rfifolock_cb(void *opaque) | |
300 | { | |
301 | /* Kick owner thread in case they are blocked in aio_poll() */ | |
302 | aio_notify(opaque); | |
303 | } | |
304 | ||
305 | static void event_notifier_dummy_cb(EventNotifier *e) | |
306 | { | |
307 | } | |
308 | ||
309 | AioContext *aio_context_new(Error **errp) | |
310 | { | |
311 | int ret; | |
312 | AioContext *ctx; | |
313 | ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext)); | |
314 | ret = event_notifier_init(&ctx->notifier, false); | |
315 | if (ret < 0) { | |
316 | g_source_destroy(&ctx->source); | |
317 | error_setg_errno(errp, -ret, "Failed to initialize event notifier"); | |
318 | return NULL; | |
319 | } | |
320 | g_source_set_can_recurse(&ctx->source, true); | |
321 | aio_set_event_notifier(ctx, &ctx->notifier, | |
322 | (EventNotifierHandler *) | |
323 | event_notifier_dummy_cb); | |
324 | ctx->thread_pool = NULL; | |
325 | qemu_mutex_init(&ctx->bh_lock); | |
326 | rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx); | |
327 | timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx); | |
328 | ||
329 | return ctx; | |
330 | } | |
331 | ||
332 | void aio_context_ref(AioContext *ctx) | |
333 | { | |
334 | g_source_ref(&ctx->source); | |
335 | } | |
336 | ||
337 | void aio_context_unref(AioContext *ctx) | |
338 | { | |
339 | g_source_unref(&ctx->source); | |
340 | } | |
341 | ||
342 | void aio_context_acquire(AioContext *ctx) | |
343 | { | |
344 | rfifolock_lock(&ctx->lock); | |
345 | } | |
346 | ||
347 | void aio_context_release(AioContext *ctx) | |
348 | { | |
349 | rfifolock_unlock(&ctx->lock); | |
350 | } |