[PATCH 08/10] combase: CoWaitForMultipleHandles should stop pumping once handles are signaled.

[Kevin Puetz]

From: Kevin Puetz

Only one message at a time should be dispatched; if that message results
in the handles becoming completed (or an APC queued, if COWAIT_ALERTABLE),
the loop should immediately stop and return that outcome.

This replaces the arbitrary "100 message" limit; RPC/DDE messages get
priority over WM_PAINT, and as long as they cause the handles to signal
there's no need to reach an empty message queue. This also fixes a
potential deadlock where MsgWaitForMultipleObjectsEx would wait for new
messages when there were actually still un-examined messages left in the
queue because the 100 message limit had been previously hit.
---
 dlls/combase/combase.c     | 12 ++++++------
 dlls/ole32/tests/compobj.c | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/dlls/combase/combase.c b/dlls/combase/combase.c
index 9d6a16b54c0..fc8414b52d3 100644
--- a/dlls/combase/combase.c
+++ b/dlls/combase/combase.c
@@ -2098,7 +2098,7 @@ HRESULT WINAPI CoWaitForMultipleHandles(DWORD flags, DWORD timeout, ULONG handle

if (message_loop)
     {
-        DWORD start_time, wait_flags = 0;
+        DWORD start_time, wait_flags = MWMO_INPUTAVAILABLE;
         struct tlsdata *tlsdata;

if (FAILED(hr = com_get_tlsdata(&tlsdata)))
@@ -2125,7 +2125,6 @@ HRESULT WINAPI CoWaitForMultipleHandles(DWORD flags, DWORD timeout, ULONG handle
             if (check_apc)
             {
                 res = WaitForMultipleObjectsEx(handle_count, handles, !!(flags & COWAIT_WAITALL), 0, TRUE);
-                check_apc = FALSE;
             }

if (res == WAIT_TIMEOUT)
@@ -2135,7 +2134,6 @@ HRESULT WINAPI CoWaitForMultipleHandles(DWORD flags, DWORD timeout, ULONG handle

if (res == WAIT_OBJECT_0 + handle_count)  /* messages available */
             {
-                int msg_count = 0;
                 MSG msg;

/* call message filter */
@@ -2165,10 +2163,9 @@ HRESULT WINAPI CoWaitForMultipleHandles(DWORD flags, DWORD timeout, ULONG handle
                     }
                 }

-                /* Some apps (e.g. Visio 2010) don't handle WM_PAINT properly and loop forever,
-                 * so after processing 100 messages we go back to checking the wait handles */
-                while (msg_count++ < 100 && com_peek_message(apt, &msg))
+                if(com_peek_message(apt, &msg))
                 {
+                    wait_flags |= MWMO_INPUTAVAILABLE;
                     if (msg.message == WM_QUIT)
                     {
                         TRACE("Received WM_QUIT message\n");
@@ -2181,6 +2178,9 @@ HRESULT WINAPI CoWaitForMultipleHandles(DWORD flags, DWORD timeout, ULONG handle
                         TranslateMessage(&msg);
                         DispatchMessageW(&msg);
                     }
+                } else {
+                    /* no interesting input remains in the queue, so block until *new* messages are posted */
+                    wait_flags &= ~MWMO_INPUTAVAILABLE;
                 }
                 continue;
             }
diff --git a/dlls/ole32/tests/compobj.c b/dlls/ole32/tests/compobj.c
index 94df7195e3c..66680ba5952 100644
--- a/dlls/ole32/tests/compobj.c
+++ b/dlls/ole32/tests/compobj.c
@@ -2953,6 +2953,17 @@ static void test_CoWaitForMultipleHandles(void)
     success = PeekMessageA(&msg, hWnd, WM_DDE_FIRST, WM_DDE_FIRST, PM_REMOVE);
     ok(!success, "CoWaitForMultipleHandles didn't pump any messages\n");

+    /* test CoWaitForMultipleHandles stops pumping messages as soon as its handles are signaled */
+    index = 0xdeadbeef;
+    PostMessageA(hWnd, WM_DDE_EXECUTE, 0, (LPARAM)execute_semaphore);
+    PostMessageA(hWnd, WM_DDE_FIRST, 0, 0);
+    hr = CoWaitForMultipleHandles(0, 50, 1, handles, &index);
+    ok(hr == S_OK, "expected S_OK, got 0x%08lx\n", hr);
+    ok(index == 0, "expected index 0, got %lu\n", index);
+    cowait_msgs_expect_queued(hWnd,WM_DDE_FIRST); /* WM_DDE_EXECUTE already pumped*/
+    success = PeekMessageA(&msg, hWnd, WM_DDE_FIRST, WM_DDE_LAST, PM_REMOVE);
+    ok(!success, "CoWaitForMultipleHandles didn't pump enough messages\n");
+
     /* test PostMessageA/SendMessageA from a different thread */

index = 0xdeadbeef;
@@ -3039,6 +3050,16 @@ static void test_CoWaitForMultipleHandles(void)
     success = PeekMessageA(&msg, hWnd, WM_DDE_FIRST, WM_DDE_FIRST, PM_REMOVE);
     ok(success, "CoWaitForMultipleHandles unexpectedly pumped messages\n");

+    index = 0xdeadbeef;
+    PostMessageA(hWnd, WM_DDE_EXECUTE, 0, (LPARAM)execute_apc);
+    PostMessageA(hWnd, WM_DDE_FIRST, 0, 0);
+    hr = CoWaitForMultipleHandles(COWAIT_ALERTABLE, 50, 1, handles, &index);
+    ok(hr == S_OK, "expected S_OK, got 0x%08lx\n", hr);
+    ok(index == WAIT_IO_COMPLETION, "expected index WAIT_IO_COMPLETION, got %lu\n", index);
+    cowait_msgs_expect_queued(hWnd,WM_DDE_FIRST); /* WM_DDE_EXECUTE already pumped*/
+    success = PeekMessageA(&msg, hWnd, WM_DDE_FIRST, WM_DDE_LAST, PM_REMOVE);
+    ok(!success, "CoWaitForMultipleHandles didn't pump enough messages\n");
+
     /* test with COWAIT_INPUTAVAILABLE (semaphores are still locked) */

index = 0xdeadbeef;