1 /* 2 * QEMU aio implementation 3 * 4 * Copyright IBM Corp., 2008 5 * Copyright Red Hat Inc., 2012 6 * 7 * Authors: 8 * Anthony Liguori <aliguori@us.ibm.com> 9 * Paolo Bonzini <pbonzini@redhat.com> 10 * 11 * This work is licensed under the terms of the GNU GPL, version 2. See 12 * the COPYING file in the top-level directory. 13 * 14 * Contributions after 2012-01-13 are licensed under the terms of the 15 * GNU GPL, version 2 or (at your option) any later version. 16 */ 17 18 #include "qemu/osdep.h" 19 #include "qemu-common.h" 20 #include "block/block.h" 21 #include "qemu/main-loop.h" 22 #include "qemu/queue.h" 23 #include "qemu/sockets.h" 24 #include "qapi/error.h" 25 #include "qemu/rcu_queue.h" 26 27 struct AioHandler { 28 EventNotifier *e; 29 IOHandler *io_read; 30 IOHandler *io_write; 31 EventNotifierHandler *io_notify; 32 GPollFD pfd; 33 int deleted; 34 void *opaque; 35 bool is_external; 36 QLIST_ENTRY(AioHandler) node; 37 }; 38 39 static void aio_remove_fd_handler(AioContext *ctx, AioHandler *node) 40 { 41 /* 42 * If the GSource is in the process of being destroyed then 43 * g_source_remove_poll() causes an assertion failure. Skip 44 * removal in that case, because glib cleans up its state during 45 * destruction anyway. 46 */ 47 if (!g_source_is_destroyed(&ctx->source)) { 48 g_source_remove_poll(&ctx->source, &node->pfd); 49 } 50 51 /* If aio_poll is in progress, just mark the node as deleted */ 52 if (qemu_lockcnt_count(&ctx->list_lock)) { 53 node->deleted = 1; 54 node->pfd.revents = 0; 55 } else { 56 /* Otherwise, delete it for real. We can't just mark it as 57 * deleted because deleted nodes are only cleaned up after 58 * releasing the list_lock. 59 */ 60 QLIST_REMOVE(node, node); 61 g_free(node); 62 } 63 } 64 65 void aio_set_fd_handler(AioContext *ctx, 66 int fd, 67 bool is_external, 68 IOHandler *io_read, 69 IOHandler *io_write, 70 AioPollFn *io_poll, 71 void *opaque) 72 { 73 /* fd is a SOCKET in our case */ 74 AioHandler *old_node; 75 AioHandler *node = NULL; 76 77 qemu_lockcnt_lock(&ctx->list_lock); 78 QLIST_FOREACH(old_node, &ctx->aio_handlers, node) { 79 if (old_node->pfd.fd == fd && !old_node->deleted) { 80 break; 81 } 82 } 83 84 if (io_read || io_write) { 85 HANDLE event; 86 long bitmask = 0; 87 88 /* Alloc and insert if it's not already there */ 89 node = g_new0(AioHandler, 1); 90 node->pfd.fd = fd; 91 92 node->pfd.events = 0; 93 if (node->io_read) { 94 node->pfd.events |= G_IO_IN; 95 } 96 if (node->io_write) { 97 node->pfd.events |= G_IO_OUT; 98 } 99 100 node->e = &ctx->notifier; 101 102 /* Update handler with latest information */ 103 node->opaque = opaque; 104 node->io_read = io_read; 105 node->io_write = io_write; 106 node->is_external = is_external; 107 108 if (io_read) { 109 bitmask |= FD_READ | FD_ACCEPT | FD_CLOSE; 110 } 111 112 if (io_write) { 113 bitmask |= FD_WRITE | FD_CONNECT; 114 } 115 116 QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, node, node); 117 event = event_notifier_get_handle(&ctx->notifier); 118 WSAEventSelect(node->pfd.fd, event, bitmask); 119 } 120 if (old_node) { 121 aio_remove_fd_handler(ctx, old_node); 122 } 123 124 qemu_lockcnt_unlock(&ctx->list_lock); 125 aio_notify(ctx); 126 } 127 128 void aio_set_fd_poll(AioContext *ctx, int fd, 129 IOHandler *io_poll_begin, 130 IOHandler *io_poll_end) 131 { 132 /* Not implemented */ 133 } 134 135 void aio_set_event_notifier(AioContext *ctx, 136 EventNotifier *e, 137 bool is_external, 138 EventNotifierHandler *io_notify, 139 AioPollFn *io_poll) 140 { 141 AioHandler *node; 142 143 qemu_lockcnt_lock(&ctx->list_lock); 144 QLIST_FOREACH(node, &ctx->aio_handlers, node) { 145 if (node->e == e && !node->deleted) { 146 break; 147 } 148 } 149 150 /* Are we deleting the fd handler? */ 151 if (!io_notify) { 152 if (node) { 153 aio_remove_fd_handler(ctx, node); 154 } 155 } else { 156 if (node == NULL) { 157 /* Alloc and insert if it's not already there */ 158 node = g_new0(AioHandler, 1); 159 node->e = e; 160 node->pfd.fd = (uintptr_t)event_notifier_get_handle(e); 161 node->pfd.events = G_IO_IN; 162 node->is_external = is_external; 163 QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, node, node); 164 165 g_source_add_poll(&ctx->source, &node->pfd); 166 } 167 /* Update handler with latest information */ 168 node->io_notify = io_notify; 169 } 170 171 qemu_lockcnt_unlock(&ctx->list_lock); 172 aio_notify(ctx); 173 } 174 175 void aio_set_event_notifier_poll(AioContext *ctx, 176 EventNotifier *notifier, 177 EventNotifierHandler *io_poll_begin, 178 EventNotifierHandler *io_poll_end) 179 { 180 /* Not implemented */ 181 } 182 183 bool aio_prepare(AioContext *ctx) 184 { 185 static struct timeval tv0; 186 AioHandler *node; 187 bool have_select_revents = false; 188 fd_set rfds, wfds; 189 190 /* 191 * We have to walk very carefully in case aio_set_fd_handler is 192 * called while we're walking. 193 */ 194 qemu_lockcnt_inc(&ctx->list_lock); 195 196 /* fill fd sets */ 197 FD_ZERO(&rfds); 198 FD_ZERO(&wfds); 199 QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { 200 if (node->io_read) { 201 FD_SET ((SOCKET)node->pfd.fd, &rfds); 202 } 203 if (node->io_write) { 204 FD_SET ((SOCKET)node->pfd.fd, &wfds); 205 } 206 } 207 208 if (select(0, &rfds, &wfds, NULL, &tv0) > 0) { 209 QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { 210 node->pfd.revents = 0; 211 if (FD_ISSET(node->pfd.fd, &rfds)) { 212 node->pfd.revents |= G_IO_IN; 213 have_select_revents = true; 214 } 215 216 if (FD_ISSET(node->pfd.fd, &wfds)) { 217 node->pfd.revents |= G_IO_OUT; 218 have_select_revents = true; 219 } 220 } 221 } 222 223 qemu_lockcnt_dec(&ctx->list_lock); 224 return have_select_revents; 225 } 226 227 bool aio_pending(AioContext *ctx) 228 { 229 AioHandler *node; 230 bool result = false; 231 232 /* 233 * We have to walk very carefully in case aio_set_fd_handler is 234 * called while we're walking. 235 */ 236 qemu_lockcnt_inc(&ctx->list_lock); 237 QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { 238 if (node->pfd.revents && node->io_notify) { 239 result = true; 240 break; 241 } 242 243 if ((node->pfd.revents & G_IO_IN) && node->io_read) { 244 result = true; 245 break; 246 } 247 if ((node->pfd.revents & G_IO_OUT) && node->io_write) { 248 result = true; 249 break; 250 } 251 } 252 253 qemu_lockcnt_dec(&ctx->list_lock); 254 return result; 255 } 256 257 static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event) 258 { 259 AioHandler *node; 260 bool progress = false; 261 AioHandler *tmp; 262 263 /* 264 * We have to walk very carefully in case aio_set_fd_handler is 265 * called while we're walking. 266 */ 267 QLIST_FOREACH_SAFE_RCU(node, &ctx->aio_handlers, node, tmp) { 268 int revents = node->pfd.revents; 269 270 if (!node->deleted && 271 (revents || event_notifier_get_handle(node->e) == event) && 272 node->io_notify) { 273 node->pfd.revents = 0; 274 node->io_notify(node->e); 275 276 /* aio_notify() does not count as progress */ 277 if (node->e != &ctx->notifier) { 278 progress = true; 279 } 280 } 281 282 if (!node->deleted && 283 (node->io_read || node->io_write)) { 284 node->pfd.revents = 0; 285 if ((revents & G_IO_IN) && node->io_read) { 286 node->io_read(node->opaque); 287 progress = true; 288 } 289 if ((revents & G_IO_OUT) && node->io_write) { 290 node->io_write(node->opaque); 291 progress = true; 292 } 293 294 /* if the next select() will return an event, we have progressed */ 295 if (event == event_notifier_get_handle(&ctx->notifier)) { 296 WSANETWORKEVENTS ev; 297 WSAEnumNetworkEvents(node->pfd.fd, event, &ev); 298 if (ev.lNetworkEvents) { 299 progress = true; 300 } 301 } 302 } 303 304 if (node->deleted) { 305 if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) { 306 QLIST_REMOVE(node, node); 307 g_free(node); 308 qemu_lockcnt_inc_and_unlock(&ctx->list_lock); 309 } 310 } 311 } 312 313 return progress; 314 } 315 316 void aio_dispatch(AioContext *ctx) 317 { 318 qemu_lockcnt_inc(&ctx->list_lock); 319 aio_bh_poll(ctx); 320 aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE); 321 qemu_lockcnt_dec(&ctx->list_lock); 322 timerlistgroup_run_timers(&ctx->tlg); 323 } 324 325 bool aio_poll(AioContext *ctx, bool blocking) 326 { 327 AioHandler *node; 328 HANDLE events[MAXIMUM_WAIT_OBJECTS + 1]; 329 bool progress, have_select_revents, first; 330 int count; 331 int timeout; 332 333 /* 334 * There cannot be two concurrent aio_poll calls for the same AioContext (or 335 * an aio_poll concurrent with a GSource prepare/check/dispatch callback). 336 * We rely on this below to avoid slow locked accesses to ctx->notify_me. 337 * 338 * aio_poll() may only be called in the AioContext's thread. iohandler_ctx 339 * is special in that it runs in the main thread, but that thread's context 340 * is qemu_aio_context. 341 */ 342 assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ? 343 qemu_get_aio_context() : ctx)); 344 progress = false; 345 346 /* aio_notify can avoid the expensive event_notifier_set if 347 * everything (file descriptors, bottom halves, timers) will 348 * be re-evaluated before the next blocking poll(). This is 349 * already true when aio_poll is called with blocking == false; 350 * if blocking == true, it is only true after poll() returns, 351 * so disable the optimization now. 352 */ 353 if (blocking) { 354 qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) + 2); 355 /* 356 * Write ctx->notify_me before computing the timeout 357 * (reading bottom half flags, etc.). Pairs with 358 * smp_mb in aio_notify(). 359 */ 360 smp_mb(); 361 } 362 363 qemu_lockcnt_inc(&ctx->list_lock); 364 have_select_revents = aio_prepare(ctx); 365 366 /* fill fd sets */ 367 count = 0; 368 QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { 369 if (!node->deleted && node->io_notify 370 && aio_node_check(ctx, node->is_external)) { 371 events[count++] = event_notifier_get_handle(node->e); 372 } 373 } 374 375 first = true; 376 377 /* ctx->notifier is always registered. */ 378 assert(count > 0); 379 380 /* Multiple iterations, all of them non-blocking except the first, 381 * may be necessary to process all pending events. After the first 382 * WaitForMultipleObjects call ctx->notify_me will be decremented. 383 */ 384 do { 385 HANDLE event; 386 int ret; 387 388 timeout = blocking && !have_select_revents 389 ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0; 390 ret = WaitForMultipleObjects(count, events, FALSE, timeout); 391 if (blocking) { 392 assert(first); 393 qatomic_store_release(&ctx->notify_me, 394 qatomic_read(&ctx->notify_me) - 2); 395 aio_notify_accept(ctx); 396 } 397 398 if (first) { 399 progress |= aio_bh_poll(ctx); 400 first = false; 401 } 402 403 /* if we have any signaled events, dispatch event */ 404 event = NULL; 405 if ((DWORD) (ret - WAIT_OBJECT_0) < count) { 406 event = events[ret - WAIT_OBJECT_0]; 407 events[ret - WAIT_OBJECT_0] = events[--count]; 408 } else if (!have_select_revents) { 409 break; 410 } 411 412 have_select_revents = false; 413 blocking = false; 414 415 progress |= aio_dispatch_handlers(ctx, event); 416 } while (count > 0); 417 418 qemu_lockcnt_dec(&ctx->list_lock); 419 420 progress |= timerlistgroup_run_timers(&ctx->tlg); 421 return progress; 422 } 423 424 void aio_context_setup(AioContext *ctx) 425 { 426 } 427 428 void aio_context_destroy(AioContext *ctx) 429 { 430 } 431 432 void aio_context_use_g_source(AioContext *ctx) 433 { 434 } 435 436 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, 437 int64_t grow, int64_t shrink, Error **errp) 438 { 439 if (max_ns) { 440 error_setg(errp, "AioContext polling is not implemented on Windows"); 441 } 442 } 443