[Xen-changelog] [qemu-upstream-unstable] aio: avoid livelock behavior for Win32

[patchbot@xxxxxxx]

commit b022b4a44abda9b6f89777b07e538be6f8f7aacb
Author: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date:   Fri Nov 23 15:59:43 2012 +0100

    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@xxxxxxxxxx>
    Signed-off-by: Anthony Liguori <aliguori@xxxxxxxxxx>
---
 aio-win32.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

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 @@ bool aio_poll(AioContext *ctx, bool blocking)
     }
 
     /* wait until next event */
-    for (;;) {
+    while (count > 0) {
         int timeout = blocking ? INFINITE : 0;
         int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 
@@ -209,6 +209,9 @@ bool aio_poll(AioContext *ctx, bool blocking)
                 g_free(tmp);
             }
         }
+
+        /* Try again, but only call each handler once.  */
+        events[ret - WAIT_OBJECT_0] = events[--count];
     }
 
     return progress;
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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