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 static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event)
  93 {
  94     AioHandler *node;
  95     bool progress = false;
  96
  97     /*
  98      * We have to walk very carefully in case aio_set_fd_handler is
  99      * called while we're walking.
 100      */
 101     node = QLIST_FIRST(&ctx->aio_handlers);
 102     while (node) {
 103         AioHandler *tmp;
 104
 105         ctx->walking_handlers++;
 106
 107         if (!node->deleted &&
 108             (node->pfd.revents || event_notifier_get_handle(node->e) == event) &&
 109             node->io_notify) {
 110             node->pfd.revents = 0;
 111             node->io_notify(node->e);
 112
 113             /* aio_notify() does not count as progress */
 114             if (node->e != &ctx->notifier) {
 115                 progress = true;
 116             }
 117         }
 118
 119         tmp = node;
 120         node = QLIST_NEXT(node, node);
 121
 122         ctx->walking_handlers--;
 123
 124         if (!ctx->walking_handlers && tmp->deleted) {
 125             QLIST_REMOVE(tmp, node);
 126             g_free(tmp);
 127         }
 128     }
 129
 130     return progress;
 131 }
 132
 133 bool aio_dispatch(AioContext *ctx)
 134 {
 135     bool progress;
 136
 137     progress = aio_bh_poll(ctx);
 138     progress |= aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE);
 139     progress |= timerlistgroup_run_timers(&ctx->tlg);
 140     return progress;
 141 }
 142
 143 bool aio_poll(AioContext *ctx, bool blocking)
 144 {
 145     AioHandler *node;
 146     HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
 147     bool was_dispatching, progress, first;
 148     int count;
 149     int timeout;
 150
 151     was_dispatching = ctx->dispatching;
 152     progress = false;
 153
 154     /* aio_notify can avoid the expensive event_notifier_set if
 155      * everything (file descriptors, bottom halves, timers) will
 156      * be re-evaluated before the next blocking poll().  This is
 157      * already true when aio_poll is called with blocking == false;
 158      * if blocking == true, it is only true after poll() returns.
 159      *
 160      * If we're in a nested event loop, ctx->dispatching might be true.
 161      * In that case we can restore it just before returning, but we
 162      * have to clear it now.
 163      */
 164     aio_set_dispatching(ctx, !blocking);
 165
 166     ctx->walking_handlers++;
 167
 168     /* fill fd sets */
 169     count = 0;
 170     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
 171         if (!node->deleted && node->io_notify) {
 172             events[count++] = event_notifier_get_handle(node->e);
 173         }
 174     }
 175
 176     ctx->walking_handlers--;
 177     first = true;
 178
 179     /* wait until next event */
 180     while (count > 0) {
 181         int ret;
 182
 183         timeout = blocking
 184             ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0;
 185         ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 186         aio_set_dispatching(ctx, true);
 187
 188         if (first && aio_bh_poll(ctx)) {
 189             progress = true;
 190         }
 191         first = false;
 192
 193         /* if we have any signaled events, dispatch event */
 194         if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
 195             break;
 196         }
 197
 198         blocking = false;
 199
 200         progress |= aio_dispatch_handlers(ctx, events[ret - WAIT_OBJECT_0]);
 201
 202         /* Try again, but only call each handler once.  */
 203         events[ret - WAIT_OBJECT_0] = events[--count];
 204     }
 205
 206     progress |= timerlistgroup_run_timers(&ctx->tlg);
 207
 208     aio_set_dispatching(ctx, was_dispatching);
 209     return progress;
 210 }