From patchwork Fri Nov 23 14:59:43 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [1.3] aio: avoid livelock behavior for Win32 Date: Fri, 23 Nov 2012 04:59:43 -0000 From: Paolo Bonzini X-Patchwork-Id: 201336 Message-Id: <1353682783-25624-1-git-send-email-pbonzini@redhat.com> To: qemu-devel@nongnu.org Cc: aliguori@us.ibm.com 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 --- Found by the new unit tests. aio-win32.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) 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;