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 "block/aio.h"
  27 #include "qemu/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
 126     for (bh = ctx->first_bh; bh; bh = bh->next) {
 127         if (!bh->deleted && bh->scheduled) {
 128             if (bh->idle) {
 129                 /* idle bottom halves will be polled at least
 130                  * every 10ms */
 131                 *timeout = 10;
 132             } else {
 133                 /* non-idle bottom halves will be executed
 134                  * immediately */
 135                 *timeout = 0;
 136                 return true;
 137             }
 138         }
 139     }
 140
 141     return false;
 142 }
 143
 144 static gboolean
 145 aio_ctx_check(GSource *source)
 146 {
 147     AioContext *ctx = (AioContext *) source;
 148     QEMUBH *bh;
 149
 150     for (bh = ctx->first_bh; bh; bh = bh->next) {
 151         if (!bh->deleted && bh->scheduled) {
 152             return true;
 153         }
 154     }
 155     return aio_pending(ctx);
 156 }
 157
 158 static gboolean
 159 aio_ctx_dispatch(GSource     *source,
 160                  GSourceFunc  callback,
 161                  gpointer     user_data)
 162 {
 163     AioContext *ctx = (AioContext *) source;
 164
 165     assert(callback == NULL);
 166     aio_poll(ctx, false);
 167     return true;
 168 }
 169
 170 static void
 171 aio_ctx_finalize(GSource     *source)
 172 {
 173     AioContext *ctx = (AioContext *) source;
 174
 175     aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
 176     event_notifier_cleanup(&ctx->notifier);
 177     g_array_free(ctx->pollfds, TRUE);
 178 }
 179
 180 static GSourceFuncs aio_source_funcs = {
 181     aio_ctx_prepare,
 182     aio_ctx_check,
 183     aio_ctx_dispatch,
 184     aio_ctx_finalize
 185 };
 186
 187 GSource *aio_get_g_source(AioContext *ctx)
 188 {
 189     g_source_ref(&ctx->source);
 190     return &ctx->source;
 191 }
 192
 193 void aio_notify(AioContext *ctx)
 194 {
 195     event_notifier_set(&ctx->notifier);
 196 }
 197
 198 AioContext *aio_context_new(void)
 199 {
 200     AioContext *ctx;
 201     ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
 202     ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
 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 }