aio-win32.c

   1 /*
   2  * QEMU aio implementation
   3  *
   4  * Copyright IBM Corp., 2008
   5  * Copyright Red Hat Inc., 2012
   6  *
   7  * Authors:
   8  *  Anthony Liguori   <aliguori@us.ibm.com>
   9  *  Paolo Bonzini     <pbonzini@redhat.com>
  10  *
  11  * This work is licensed under the terms of the GNU GPL, version 2.  See
  12  * the COPYING file in the top-level directory.
  13  *
  14  * Contributions after 2012-01-13 are licensed under the terms of the
  15  * GNU GPL, version 2 or (at your option) any later version.
  16  */
  17
  18 #include "qemu-common.h"
  19 #include "block/block.h"
  20 #include "qemu/queue.h"
  21 #include "qemu/sockets.h"
  22
  23 struct AioHandler {
  24     EventNotifier *e;
  25     EventNotifierHandler *io_notify;
  26     GPollFD pfd;
  27     int deleted;
  28     QLIST_ENTRY(AioHandler) node;
  29 };
  30
  31 void aio_set_event_notifier(AioContext *ctx,
  32                             EventNotifier *e,
  33                             EventNotifierHandler *io_notify)
  34 {
  35     AioHandler *node;
  36
  37     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
  38         if (node->e == e && !node->deleted) {
  39             break;
  40         }
  41     }
  42
  43     /* Are we deleting the fd handler? */
  44     if (!io_notify) {
  45         if (node) {
  46             g_source_remove_poll(&ctx->source, &node->pfd);
  47
  48             /* If the lock is held, just mark the node as deleted */
  49             if (ctx->walking_handlers) {
  50                 node->deleted = 1;
  51                 node->pfd.revents = 0;
  52             } else {
  53                 /* Otherwise, delete it for real.  We can't just mark it as
  54                  * deleted because deleted nodes are only cleaned up after
  55                  * releasing the walking_handlers lock.
  56                  */
  57                 QLIST_REMOVE(node, node);
  58                 g_free(node);
  59             }
  60         }
  61     } else {
  62         if (node == NULL) {
  63             /* Alloc and insert if it's not already there */
  64             node = g_malloc0(sizeof(AioHandler));
  65             node->e = e;
  66             node->pfd.fd = (uintptr_t)event_notifier_get_handle(e);
  67             node->pfd.events = G_IO_IN;
  68             QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
  69
  70             g_source_add_poll(&ctx->source, &node->pfd);
  71         }
  72         /* Update handler with latest information */
  73         node->io_notify = io_notify;
  74     }
  75
  76     aio_notify(ctx);
  77 }
  78
  79 bool aio_pending(AioContext *ctx)
  80 {
  81     AioHandler *node;
  82
  83     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
  84         if (node->pfd.revents && node->io_notify) {
  85             return true;
  86         }
  87     }
  88
  89     return false;
  90 }
  91
  92 bool aio_poll(AioContext *ctx, bool blocking)
  93 {
  94     AioHandler *node;
  95     HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
  96     bool progress;
  97     int count;
  98
  99     progress = false;
 100
 101     /*
 102      * If there are callbacks left that have been queued, we need to call then.
 103      * Do not call select in this case, because it is possible that the caller
 104      * does not need a complete flush (as is the case for qemu_aio_wait loops).
 105      */
 106     if (aio_bh_poll(ctx)) {
 107         blocking = false;
 108         progress = true;
 109     }
 110
 111     /*
 112      * Then dispatch any pending callbacks from the GSource.
 113      *
 114      * We have to walk very carefully in case qemu_aio_set_fd_handler is
 115      * called while we're walking.
 116      */
 117     node = QLIST_FIRST(&ctx->aio_handlers);
 118     while (node) {
 119         AioHandler *tmp;
 120
 121         ctx->walking_handlers++;
 122
 123         if (node->pfd.revents && node->io_notify) {
 124             node->pfd.revents = 0;
 125             node->io_notify(node->e);
 126
 127             /* aio_notify() does not count as progress */
 128             if (node->opaque != &ctx->notifier) {
 129                 progress = true;
 130             }
 131         }
 132
 133         tmp = node;
 134         node = QLIST_NEXT(node, node);
 135
 136         ctx->walking_handlers--;
 137
 138         if (!ctx->walking_handlers && tmp->deleted) {
 139             QLIST_REMOVE(tmp, node);
 140             g_free(tmp);
 141         }
 142     }
 143
 144     if (progress && !blocking) {
 145         return true;
 146     }
 147
 148     ctx->walking_handlers++;
 149
 150     /* fill fd sets */
 151     count = 0;
 152     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
 153         if (!node->deleted && node->io_notify) {
 154             events[count++] = event_notifier_get_handle(node->e);
 155         }
 156     }
 157
 158     ctx->walking_handlers--;
 159
 160     /* early return if we only have the aio_notify() fd */
 161     if (count == 1) {
 162         return progress;
 163     }
 164
 165     /* wait until next event */
 166     while (count > 0) {
 167         int timeout = blocking ? INFINITE : 0;
 168         int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 169
 170         /* if we have any signaled events, dispatch event */
 171         if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
 172             break;
 173         }
 174
 175         blocking = false;
 176
 177         /* we have to walk very carefully in case
 178          * qemu_aio_set_fd_handler is called while we're walking */
 179         node = QLIST_FIRST(&ctx->aio_handlers);
 180         while (node) {
 181             AioHandler *tmp;
 182
 183             ctx->walking_handlers++;
 184
 185             if (!node->deleted &&
 186                 event_notifier_get_handle(node->e) == events[ret - WAIT_OBJECT_0] &&
 187                 node->io_notify) {
 188                 node->io_notify(node->e);
 189
 190                 /* aio_notify() does not count as progress */
 191                 if (node->opaque != &ctx->notifier) {
 192                     progress = true;
 193                 }
 194             }
 195
 196             tmp = node;
 197             node = QLIST_NEXT(node, node);
 198
 199             ctx->walking_handlers--;
 200
 201             if (!ctx->walking_handlers && tmp->deleted) {
 202                 QLIST_REMOVE(tmp, node);
 203                 g_free(tmp);
 204             }
 205         }
 206
 207         /* Try again, but only call each handler once.  */
 208         events[ret - WAIT_OBJECT_0] = events[--count];
 209     }
 210
 211     return progress;
 212 }