diff mbox

[PULL,for-2.4,3/4] aio-win32: reorganize polling loop

Message ID 1437415513-21435-4-git-send-email-stefanha@redhat.com
State New
Headers show

Commit Message

Stefan Hajnoczi July 20, 2015, 6:05 p.m. UTC 
From: Paolo Bonzini <pbonzini@redhat.com>

Preparatory bugfixes and tweaks to the loop before the next patch:

- disable dispatch optimization during aio_prepare.  This fixes a bug.

- do not modify "blocking" until after the first WaitForMultipleObjects
call.  This is needed in the next patch.

- change the loop to do...while.  This makes it obvious that the loop
is always entered at least once.  In the next patch this is important
because the first iteration undoes the ctx->notify_me increment that
happened before entering the loop.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1437250891-18715-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 aio-win32.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)
diff mbox

Patch

diff --git a/aio-win32.c b/aio-win32.c
index 233d8f5..9268b5c 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -284,11 +284,6 @@  bool aio_poll(AioContext *ctx, bool blocking)
     int timeout;
 
     aio_context_acquire(ctx);
-    have_select_revents = aio_prepare(ctx);
-    if (have_select_revents) {
-        blocking = false;
-    }
-
     was_dispatching = ctx->dispatching;
     progress = false;
 
@@ -304,6 +299,8 @@  bool aio_poll(AioContext *ctx, bool blocking)
      */
     aio_set_dispatching(ctx, !blocking);
 
+    have_select_revents = aio_prepare(ctx);
+
     ctx->walking_handlers++;
 
     /* fill fd sets */
@@ -317,12 +314,18 @@  bool aio_poll(AioContext *ctx, bool blocking)
     ctx->walking_handlers--;
     first = true;
 
-    /* wait until next event */
-    while (count > 0) {
+    /* ctx->notifier is always registered.  */
+    assert(count > 0);
+
+    /* Multiple iterations, all of them non-blocking except the first,
+     * may be necessary to process all pending events.  After the first
+     * WaitForMultipleObjects call ctx->notify_me will be decremented.
+     */
+    do {
         HANDLE event;
         int ret;
 
-        timeout = blocking
+        timeout = blocking && !have_select_revents
             ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0;
         if (timeout) {
             aio_context_release(ctx);
@@ -351,7 +354,7 @@  bool aio_poll(AioContext *ctx, bool blocking)
         blocking = false;
 
         progress |= aio_dispatch_handlers(ctx, event);
-    }
+    } while (count > 0);
 
     progress |= timerlistgroup_run_timers(&ctx->tlg);