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     AioContext *ctx;
  34     QEMUBHFunc *cb;
  35     void *opaque;
  36     QEMUBH *next;
  37     bool scheduled;
  38     bool idle;
  39     bool deleted;
  40 };
  41
  42 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
  43 {
  44     QEMUBH *bh;
  45     bh = g_malloc0(sizeof(QEMUBH));
  46     bh->ctx = ctx;
  47     bh->cb = cb;
  48     bh->opaque = opaque;
  49     bh->next = ctx->first_bh;
  50     ctx->first_bh = bh;
  51     return bh;
  52 }
  53
  54 int aio_bh_poll(AioContext *ctx)
  55 {
  56     QEMUBH *bh, **bhp, *next;
  57     int ret;
  58
  59     ctx->walking_bh++;
  60
  61     ret = 0;
  62     for (bh = ctx->first_bh; bh; bh = next) {
  63         next = bh->next;
  64         if (!bh->deleted && bh->scheduled) {
  65             bh->scheduled = 0;
  66             if (!bh->idle)
  67                 ret = 1;
  68             bh->idle = 0;
  69             bh->cb(bh->opaque);
  70         }
  71     }
  72
  73     ctx->walking_bh--;
  74
  75     /* remove deleted bhs */
  76     if (!ctx->walking_bh) {
  77         bhp = &ctx->first_bh;
  78         while (*bhp) {
  79             bh = *bhp;
  80             if (bh->deleted) {
  81                 *bhp = bh->next;
  82                 g_free(bh);
  83             } else {
  84                 bhp = &bh->next;
  85             }
  86         }
  87     }
  88
  89     return ret;
  90 }
  91
  92 void qemu_bh_schedule_idle(QEMUBH *bh)
  93 {
  94     if (bh->scheduled)
  95         return;
  96     bh->scheduled = 1;
  97     bh->idle = 1;
  98 }
  99
 100 void qemu_bh_schedule(QEMUBH *bh)
 101 {
 102     if (bh->scheduled)
 103         return;
 104     bh->scheduled = 1;
 105     bh->idle = 0;
 106     aio_notify(bh->ctx);
 107 }
 108
 109 void qemu_bh_cancel(QEMUBH *bh)
 110 {
 111     bh->scheduled = 0;
 112 }
 113
 114 void qemu_bh_delete(QEMUBH *bh)
 115 {
 116     bh->scheduled = 0;
 117     bh->deleted = 1;
 118 }
 119
 120 static gboolean
 121 aio_ctx_prepare(GSource *source, gint    *timeout)
 122 {
 123     AioContext *ctx = (AioContext *) source;
 124     QEMUBH *bh;
 125     bool scheduled = false;
 126
 127     for (bh = ctx->first_bh; bh; bh = bh->next) {
 128         if (!bh->deleted && bh->scheduled) {
 129             scheduled = true;
 130             if (bh->idle) {
 131                 /* idle bottom halves will be polled at least
 132                  * every 10ms */
 133                 *timeout = 10;
 134             } else {
 135                 /* non-idle bottom halves will be executed
 136                  * immediately */
 137                 *timeout = 0;
 138                 break;
 139             }
 140         }
 141     }
 142
 143     return scheduled;
 144 }
 145
 146 static gboolean
 147 aio_ctx_check(GSource *source)
 148 {
 149     AioContext *ctx = (AioContext *) source;
 150     QEMUBH *bh;
 151
 152     for (bh = ctx->first_bh; bh; bh = bh->next) {
 153         if (!bh->deleted && bh->scheduled) {
 154             return true;
 155         }
 156     }
 157     return aio_pending(ctx);
 158 }
 159
 160 static gboolean
 161 aio_ctx_dispatch(GSource     *source,
 162                  GSourceFunc  callback,
 163                  gpointer     user_data)
 164 {
 165     AioContext *ctx = (AioContext *) source;
 166
 167     assert(callback == NULL);
 168     aio_poll(ctx, false);
 169     return true;
 170 }
 171
 172 static void
 173 aio_ctx_finalize(GSource     *source)
 174 {
 175     AioContext *ctx = (AioContext *) source;
 176
 177     aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
 178     event_notifier_cleanup(&ctx->notifier);
 179 }
 180
 181 static GSourceFuncs aio_source_funcs = {
 182     aio_ctx_prepare,
 183     aio_ctx_check,
 184     aio_ctx_dispatch,
 185     aio_ctx_finalize
 186 };
 187
 188 GSource *aio_get_g_source(AioContext *ctx)
 189 {
 190     g_source_ref(&ctx->source);
 191     return &ctx->source;
 192 }
 193
 194 void aio_notify(AioContext *ctx)
 195 {
 196     event_notifier_set(&ctx->notifier);
 197 }
 198
 199 AioContext *aio_context_new(void)
 200 {
 201     AioContext *ctx;
 202     ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
 203     event_notifier_init(&ctx->notifier, false);
 204     aio_set_event_notifier(ctx, &ctx->notifier,
 205                            (EventNotifierHandler *)
 206                            event_notifier_test_and_clear, NULL);
 207
 208     return ctx;
 209 }
 210
 211 void aio_context_ref(AioContext *ctx)
 212 {
 213     g_source_ref(&ctx->source);
 214 }
 215
 216 void aio_context_unref(AioContext *ctx)
 217 {
 218     g_source_unref(&ctx->source);
 219 }
 220
 221 void aio_flush(AioContext *ctx)
 222 {
 223     while (aio_poll(ctx, true));
 224 }