async.c

   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 "qemu-aio.h"
  27 #include "main-loop.h"
  28
  29 /***********************************************************/
  30 /* bottom halves (can be seen as timers which expire ASAP) */
  31
  32 struct QEMUBH {
  33     QEMUBHFunc *cb;
  34     void *opaque;
  35     QEMUBH *next;
  36     bool scheduled;
  37     bool idle;
  38     bool deleted;
  39 };
  40
  41 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
  42 {
  43     QEMUBH *bh;
  44     bh = g_malloc0(sizeof(QEMUBH));
  45     bh->cb = cb;
  46     bh->opaque = opaque;
  47     bh->next = ctx->first_bh;
  48     ctx->first_bh = bh;
  49     return bh;
  50 }
  51
  52 int aio_bh_poll(AioContext *ctx)
  53 {
  54     QEMUBH *bh, **bhp, *next;
  55     int ret;
  56
  57     ctx->walking_bh++;
  58
  59     ret = 0;
  60     for (bh = ctx->first_bh; bh; bh = next) {
  61         next = bh->next;
  62         if (!bh->deleted && bh->scheduled) {
  63             bh->scheduled = 0;
  64             if (!bh->idle)
  65                 ret = 1;
  66             bh->idle = 0;
  67             bh->cb(bh->opaque);
  68         }
  69     }
  70
  71     ctx->walking_bh--;
  72
  73     /* remove deleted bhs */
  74     if (!ctx->walking_bh) {
  75         bhp = &ctx->first_bh;
  76         while (*bhp) {
  77             bh = *bhp;
  78             if (bh->deleted) {
  79                 *bhp = bh->next;
  80                 g_free(bh);
  81             } else {
  82                 bhp = &bh->next;
  83             }
  84         }
  85     }
  86
  87     return ret;
  88 }
  89
  90 void qemu_bh_schedule_idle(QEMUBH *bh)
  91 {
  92     if (bh->scheduled)
  93         return;
  94     bh->scheduled = 1;
  95     bh->idle = 1;
  96 }
  97
  98 void qemu_bh_schedule(QEMUBH *bh)
  99 {
 100     if (bh->scheduled)
 101         return;
 102     bh->scheduled = 1;
 103     bh->idle = 0;
 104     /* stop the currently executing CPU to execute the BH ASAP */
 105     qemu_notify_event();
 106 }
 107
 108 void qemu_bh_cancel(QEMUBH *bh)
 109 {
 110     bh->scheduled = 0;
 111 }
 112
 113 void qemu_bh_delete(QEMUBH *bh)
 114 {
 115     bh->scheduled = 0;
 116     bh->deleted = 1;
 117 }
 118
 119 void aio_bh_update_timeout(AioContext *ctx, uint32_t *timeout)
 120 {
 121     QEMUBH *bh;
 122
 123     for (bh = ctx->first_bh; bh; bh = bh->next) {
 124         if (!bh->deleted && bh->scheduled) {
 125             if (bh->idle) {
 126                 /* idle bottom halves will be polled at least
 127                  * every 10ms */
 128                 *timeout = MIN(10, *timeout);
 129             } else {
 130                 /* non-idle bottom halves will be executed
 131                  * immediately */
 132                 *timeout = 0;
 133                 break;
 134             }
 135         }
 136     }
 137 }
 138
 139
 140 AioContext *aio_context_new(void)
 141 {
 142     return g_new0(AioContext, 1);
 143 }
 144
 145 void aio_flush(AioContext *ctx)
 146 {
 147     while (aio_poll(ctx, true));
 148 }