commit b022b4a44abda9b6f89777b07e538be6f8f7aacb
author Paolo Bonzini <pbonzini@redhat.com> Fri Nov 23 15:59:43 2012 +0100
committer Anthony Liguori <aliguori@us.ibm.com> Mon Nov 26 09:37:06 2012 -0600
tree 930770a31ba76f6071b6f2d79423e2aa76fe2173
parent 21022c92dc5095324ceb3effc068b5ff81642125

aio: avoid livelock behavior for Win32

The repeated calls to WaitForMultipleObjects may cause a livelock in aio_poll,
where no progress is made on bottom halves.  This patch matches the behavior
of the POSIX code.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

aio-win32.c

diff --git a/aio-win32.c b/aio-win32.c
index a84eb71..cec4646 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -173,7 +173,7 @@
     }
 
     /* wait until next event */
-    for (;;) {
+    while (count > 0) {
         int timeout = blocking ? INFINITE : 0;
         int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 
@@ -209,6 +209,9 @@
                 g_free(tmp);
             }
         }
+
+        /* Try again, but only call each handler once.  */
+        events[ret - WAIT_OBJECT_0] = events[--count];
     }
 
     return progress;