1 /* 2 * AioContext wait support 3 * 4 * Copyright (C) 2018 Red Hat, Inc. 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 "qemu/main-loop.h" 27 #include "block/aio-wait.h" 28 29 AioWait global_aio_wait; 30 31 static void dummy_bh_cb(void *opaque) 32 { 33 /* The point is to make AIO_WAIT_WHILE()'s aio_poll() return */ 34 } 35 36 void aio_wait_kick(void) 37 { 38 /* 39 * Paired with smp_mb in AIO_WAIT_WHILE. Here we have: 40 * write(condition); 41 * aio_wait_kick() { 42 * smp_mb(); 43 * read(num_waiters); 44 * } 45 * 46 * And in AIO_WAIT_WHILE: 47 * write(num_waiters); 48 * smp_mb(); 49 * read(condition); 50 */ 51 smp_mb(); 52 53 if (qatomic_read(&global_aio_wait.num_waiters)) { 54 aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL); 55 } 56 } 57 58 typedef struct { 59 bool done; 60 QEMUBHFunc *cb; 61 void *opaque; 62 } AioWaitBHData; 63 64 /* Context: BH in IOThread */ 65 static void aio_wait_bh(void *opaque) 66 { 67 AioWaitBHData *data = opaque; 68 69 data->cb(data->opaque); 70 71 data->done = true; 72 aio_wait_kick(); 73 } 74 75 void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) 76 { 77 AioWaitBHData data = { 78 .cb = cb, 79 .opaque = opaque, 80 }; 81 82 assert(qemu_get_current_aio_context() == qemu_get_aio_context()); 83 84 aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data); 85 AIO_WAIT_WHILE(ctx, !data.done); 86 } 87