qemu

FORK: QEMU emulator
git clone https://git.neptards.moe/neptards/qemu.git
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aio-wait.c (2425B)

      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 }