Nikolay Sivov : evr/sample: Avoid a race condition when releasing a tracked sample.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: ce71f5a05f226b3f68328d4632cd78ac9440d073
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=ce71f5a05f226b3f68328d4632cd78ac9440d073

Author: Nikolay Sivov <nsivov at codeweavers.com>
Date:   Tue May 10 19:16:17 2022 +0300

evr/sample: Avoid a race condition when releasing a tracked sample.

Same as b1807751219e256867eaac5cc4d8b97a5482978f.

Signed-off-by: Nikolay Sivov <nsivov at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>

---

 dlls/evr/sample.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/dlls/evr/sample.c b/dlls/evr/sample.c
index 1d29b6cdc2c..738f803fe66 100644
--- a/dlls/evr/sample.c
+++ b/dlls/evr/sample.c
@@ -920,19 +920,21 @@ static ULONG WINAPI video_sample_AddRef(IMFSample *iface)
 static ULONG WINAPI video_sample_Release(IMFSample *iface)
 {
     struct video_sample *sample = impl_from_IMFSample(iface);
-    ULONG refcount;
+    ULONG refcount = InterlockedDecrement(&sample->refcount);
+    IMFAsyncResult *tracked_result = NULL;
 
     IMFSample_LockStore(sample->sample);
-    if (sample->tracked_result && sample->tracked_refcount == (sample->refcount - 1))
+    if (sample->tracked_result && sample->tracked_refcount == refcount)
     {
-        video_sample_tracking_thread_invoke(sample->tracked_result);
-        IMFAsyncResult_Release(sample->tracked_result);
+        tracked_result = sample->tracked_result;
+        video_sample_tracking_thread_invoke(tracked_result);
         sample->tracked_result = NULL;
         sample->tracked_refcount = 0;
     }
     IMFSample_UnlockStore(sample->sample);
 
-    refcount = InterlockedDecrement(&sample->refcount);
+    if (tracked_result)
+        IMFAsyncResult_Release(tracked_result);
 
     TRACE("%p, refcount %lu.\n", iface, refcount);