[PATCH 1/1] combase: Use SendMessageW() in ClientRpcChannelBuffer_SendReceive() for STAs.

[Zhiyi Zhang]

From: Zhiyi Zhang

An application has a thread 1 sending WM_DESTROY to windows in thread 2. When handling the message
in thread 2, RevokeDragDrop() is called to release a COM object in thread 1. Then deadlock happens
when using PostMessageW() because the DM_EXECUTERPC message will not be handled as thread 1 is still
waiting for thread 2 to finish handling WM_DESTROY.
---
 dlls/combase/rpc.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/dlls/combase/rpc.c b/dlls/combase/rpc.c
index c51b59de4bf..1862c8bddca 100644
--- a/dlls/combase/rpc.c
+++ b/dlls/combase/rpc.c
@@ -1416,16 +1416,7 @@ static HRESULT WINAPI ClientRpcChannelBuffer_SendReceive(LPRPCCHANNELBUFFER ifac

msg->ProcNum &= ~RPC_FLAGS_VALID_BIT;

-        if (!PostMessageW(message_state->target_hwnd, DM_EXECUTERPC, 0,
-                          (LPARAM)&message_state->params))
-        {
-            ERR("PostMessage failed with error %lu\n", GetLastError());
-
-            /* Note: message_state->params.iface doesn't have a reference and
-             * so doesn't need to be released */
-
-            hr = HRESULT_FROM_WIN32(GetLastError());
-        }
+        SendMessageW(message_state->target_hwnd, DM_EXECUTERPC, 0, (LPARAM)&message_state->params);
     }
     else
     {