[PATCH 1/1] win32u: Release the Win16 mutex when yielding in peek_message.

[Rémi Bernon]

From: Rémi Bernon

This is important for other Win16 threads to have a chance to execute
during peek_message, even if no messages are received, or if the thread
is within a nested window message procedure call.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57384
---
 dlls/win32u/message.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/dlls/win32u/message.c b/dlls/win32u/message.c
index ee3f2521fa4..ef8b6f86431 100644
--- a/dlls/win32u/message.c
+++ b/dlls/win32u/message.c
@@ -3270,8 +3270,20 @@ BOOL WINAPI NtUserPeekMessage( MSG *msg_out, HWND hwnd, UINT first, UINT last, U
     {
         if (!ret)
         {
+            struct thunk_lock_params params = {.dispatch.callback = thunk_lock_callback};
+            void *ret_ptr;
+            ULONG ret_len;
+
             flush_window_surfaces( TRUE );
+
+            if (!KeUserDispatchCallback( &params.dispatch, sizeof(params), &ret_ptr, &ret_len ) &&
+                ret_len == sizeof(params.locks))
+            {
+                params.locks = *(DWORD *)ret_ptr;
+                params.restore = TRUE;
+            }
             NtYieldExecution();
+            KeUserDispatchCallback( &params.dispatch, sizeof(params), &ret_ptr, &ret_len );
         }
         return FALSE;
     }