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.h"
  20 #include "qemu-queue.h"
  21 #include "qemu_socket.h"
  22
  23 struct AioHandler {
  24     EventNotifier *e;
  25     EventNotifierHandler *io_notify;
  26     AioFlushEventNotifierHandler *io_flush;
  27     GPollFD pfd;
  28     int deleted;
  29     QLIST_ENTRY(AioHandler) node;
  30 };
  31
  32 void aio_set_event_notifier(AioContext *ctx,
  33                             EventNotifier *e,
  34                             EventNotifierHandler *io_notify,
  35                             AioFlushEventNotifierHandler *io_flush)
  36 {
  37     AioHandler *node;
  38
  39     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
  40         if (node->e == e && !node->deleted) {
  41             break;
  42         }
  43     }
  44
  45     /* Are we deleting the fd handler? */
  46     if (!io_notify) {
  47         if (node) {
  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         /* Update handler with latest information */
  71         node->io_notify = io_notify;
  72         node->io_flush = io_flush;
  73     }
  74 }
  75
  76 bool aio_pending(AioContext *ctx)
  77 {
  78     AioHandler *node;
  79
  80     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
  81         if (node->pfd.revents && node->io_notify) {
  82             return true;
  83         }
  84     }
  85
  86     return false;
  87 }
  88
  89 bool aio_poll(AioContext *ctx, bool blocking)
  90 {
  91     AioHandler *node;
  92     HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
  93     bool busy, progress;
  94     int count;
  95
  96     progress = false;
  97
  98     /*
  99      * If there are callbacks left that have been queued, we need to call then.
 100      * Do not call select in this case, because it is possible that the caller
 101      * does not need a complete flush (as is the case for qemu_aio_wait loops).
 102      */
 103     if (aio_bh_poll(ctx)) {
 104         blocking = false;
 105         progress = true;
 106     }
 107
 108     /*
 109      * Then dispatch any pending callbacks from the GSource.
 110      *
 111      * We have to walk very carefully in case qemu_aio_set_fd_handler is
 112      * called while we're walking.
 113      */
 114     node = QLIST_FIRST(&ctx->aio_handlers);
 115     while (node) {
 116         AioHandler *tmp;
 117
 118         ctx->walking_handlers++;
 119
 120         if (node->pfd.revents && node->io_notify) {
 121             node->pfd.revents = 0;
 122             node->io_notify(node->e);
 123             progress = true;
 124         }
 125
 126         tmp = node;
 127         node = QLIST_NEXT(node, node);
 128
 129         ctx->walking_handlers--;
 130
 131         if (!ctx->walking_handlers && tmp->deleted) {
 132             QLIST_REMOVE(tmp, node);
 133             g_free(tmp);
 134         }
 135     }
 136
 137     if (progress && !blocking) {
 138         return true;
 139     }
 140
 141     ctx->walking_handlers++;
 142
 143     /* fill fd sets */
 144     busy = false;
 145     count = 0;
 146     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
 147         /* If there aren't pending AIO operations, don't invoke callbacks.
 148          * Otherwise, if there are no AIO requests, qemu_aio_wait() would
 149          * wait indefinitely.
 150          */
 151         if (!node->deleted && node->io_flush) {
 152             if (node->io_flush(node->e) == 0) {
 153                 continue;
 154             }
 155             busy = true;
 156         }
 157         if (!node->deleted && node->io_notify) {
 158             events[count++] = event_notifier_get_handle(node->e);
 159         }
 160     }
 161
 162     ctx->walking_handlers--;
 163
 164     /* No AIO operations?  Get us out of here */
 165     if (!busy) {
 166         return progress;
 167     }
 168
 169     /* wait until next event */
 170     for (;;) {
 171         int timeout = blocking ? INFINITE : 0;
 172         int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 173
 174         /* if we have any signaled events, dispatch event */
 175         if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
 176             break;
 177         }
 178
 179         blocking = false;
 180
 181         /* we have to walk very carefully in case
 182          * qemu_aio_set_fd_handler is called while we're walking */
 183         node = QLIST_FIRST(&ctx->aio_handlers);
 184         while (node) {
 185             AioHandler *tmp;
 186
 187             ctx->walking_handlers++;
 188
 189             if (!node->deleted &&
 190                 event_notifier_get_handle(node->e) == events[ret - WAIT_OBJECT_0] &&
 191                 node->io_notify) {
 192                 node->io_notify(node->e);
 193                 progress = true;
 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
 208     return progress;
 209 }