Avoid DefaultDrmSessionManager releasing too many session references

Before this fix, if DefaultDrmSessionManager.release() was called while
there was at least one 'external' session reference still active (i.e.
session.referenceCount > 1) then the manager will release it's reference
immediately but when the session's reference count subsequently drops to
1 (due to external references being released) the manager will schedule
a task to release its internal reference *again*.

This change fixes the problem by only scheduling the timed release if
the manager is unreleased. This ensures that the internal references
are only released once.

Issue: #9193

PiperOrigin-RevId: 385580741

RELEASENOTES.md

@@ -45,6 +45,10 @@
         ([#9106](https://github.com/google/ExoPlayer/issues/9106).
 *   DRM:
     *   Allow repeated provisioning in `DefaultDrmSession(Manager)`.
+    *   Fix a crash due to `DefaultDrmSessionManager.release()` incorrectly
+        releasing too many keep-alive `DefaultDrmSession` references, resulting
+        in `DefaultDrmSession.release()` throwing an `IllegalStateException`
+        ([#9193](https://github.com/google/ExoPlayer/issues/9193)).
 *   Metadata:
     *   Fix handling of emsg messages with an unset duration
         ([#9123](https://github.com/google/ExoPlayer/issues/9123)).

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManager.java

@@ -911,8 +911,10 @@ public class DefaultDrmSessionManager implements DrmSessionManager {
 
     @Override
     public void onReferenceCountDecremented(DefaultDrmSession session, int newReferenceCount) {
-      if (newReferenceCount == 1 && sessionKeepaliveMs != C.TIME_UNSET) {
-        // Only the internal keep-alive reference remains, so we can start the timeout.
+      if (newReferenceCount == 1 && prepareCallsCount > 0 && sessionKeepaliveMs != C.TIME_UNSET) {
+        // Only the internal keep-alive reference remains, so we can start the timeout. We only
+        // do this if the manager isn't released, because a released manager has already released
+        // all its internal session keep-alive references.
         keepaliveSessions.add(session);
         checkNotNull(playbackHandler)
             .postAtTime(

library/core/src/test/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManagerTest.java

@@ -222,6 +222,44 @@ public class DefaultDrmSessionManagerTest {
     exoMediaDrm.release();
   }
 
+  // https://github.com/google/ExoPlayer/issues/9193
+  @Test(timeout = 10_000)
+  public void
+      managerReleasedBeforeSession_keepaliveEnabled_managerOnlyReleasesOneKeepaliveReference()
+          throws Exception {
+    FakeExoMediaDrm.LicenseServer licenseServer =
+        FakeExoMediaDrm.LicenseServer.allowingSchemeDatas(DRM_SCHEME_DATAS);
+    FakeExoMediaDrm exoMediaDrm = new FakeExoMediaDrm.Builder().build();
+    DrmSessionManager drmSessionManager =
+        new DefaultDrmSessionManager.Builder()
+            .setUuidAndExoMediaDrmProvider(DRM_SCHEME_UUID, new AppManagedProvider(exoMediaDrm))
+            .setSessionKeepaliveMs(10_000)
+            .build(/* mediaDrmCallback= */ licenseServer);
+
+    drmSessionManager.prepare();
+    DrmSession drmSession =
+        checkNotNull(
+            drmSessionManager.acquireSession(
+                /* playbackLooper= */ checkNotNull(Looper.myLooper()),
+                /* eventDispatcher= */ null,
+                FORMAT_WITH_DRM_INIT_DATA));
+    waitForOpenedWithKeys(drmSession);
+
+    // Release the manager (there's still an explicit reference to the session from acquireSession).
+    // This should immediately release the manager's internal keepalive session reference.
+    drmSessionManager.release();
+    assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_OPENED_WITH_KEYS);
+
+    // Ensure the manager doesn't release a *second* keepalive session reference after the timer
+    // expires.
+    ShadowLooper.idleMainLooper(10, SECONDS);
+    assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_OPENED_WITH_KEYS);
+
+    // Release the explicit session reference.
+    drmSession.release(/* eventDispatcher= */ null);
+    assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_RELEASED);
+  }
+
   @Test(timeout = 10_000)
   public void maxConcurrentSessionsExceeded_allKeepAliveSessionsEagerlyReleased() throws Exception {
     ImmutableList<DrmInitData.SchemeData> secondSchemeDatas =