Giovanni Mascellani : mfplat: Avoid a race condition when releasing a tracked sample.

[Alexandre Julliard]

Module: wine
Branch: stable
Commit: 967b3294fa25202823af16758a148844cbcab967
URL:    https://gitlab.winehq.org/wine/wine/-/commit/967b3294fa25202823af16758a14884...

Author: Giovanni Mascellani 
Date:   Tue May  3 15:06:43 2022 +0200

mfplat: Avoid a race condition when releasing a tracked sample.

Right now, if the same tracked sample is released at the same time
from two different threads it might happen that neither of them calls
the callback, because they might go through the critical section at
the same time (while neither has decremented the reference count yet).

Signed-off-by: Giovanni Mascellani 
Signed-off-by: Alexandre Julliard 
(cherry picked from commit b1807751219e256867eaac5cc4d8b97a5482978f)
Conflicts:
    dlls/mfplat/sample.c
Signed-off-by: Michael Stefaniuc

---

dlls/mfplat/sample.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/dlls/mfplat/sample.c b/dlls/mfplat/sample.c
index 04c68c87199..600e3bd929e 100644
--- a/dlls/mfplat/sample.c
+++ b/dlls/mfplat/sample.c
@@ -183,11 +183,11 @@ static ULONG WINAPI sample_Release(IMFSample *iface)
 static ULONG WINAPI sample_tracked_Release(IMFSample *iface)
 {
     struct sample *sample = impl_from_IMFSample(iface);
-    ULONG refcount;
+    ULONG refcount = InterlockedDecrement(&sample->attributes.ref);
     HRESULT hr;

EnterCriticalSection(&sample->attributes.cs);
-    if (sample->tracked_result && sample->tracked_refcount == (sample->attributes.ref - 1))
+    if (sample->tracked_result && sample->tracked_refcount == refcount)
     {
         IRtwqAsyncResult *tracked_result = sample->tracked_result;
         sample->tracked_result = NULL;
@@ -200,8 +200,6 @@ static ULONG WINAPI sample_tracked_Release(IMFSample *iface)
     }
     LeaveCriticalSection(&sample->attributes.cs);

-    refcount = InterlockedDecrement(&sample->attributes.ref);
-
     TRACE("%p, refcount %u.\n", iface, refcount);

if (!refcount)