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