platforms/drm: release gbm buffers before eglDestroySurface

BUG: 436500

src/plugins/platforms/drm/drm_buffer.h

@@ -25,6 +25,8 @@ public:
 
     virtual bool needsModeChange(DrmBuffer *b) const {Q_UNUSED(b) return false;}
 
+    virtual void releaseGbm() {}
+
     quint32 bufferId() const {
         return m_bufferId;
     }

src/plugins/platforms/drm/drm_buffer_gbm.cpp

@@ -45,15 +45,21 @@ GbmBuffer::GbmBuffer(gbm_bo *buffer, KWaylandServer::BufferInterface *bufferInte
 }
 
 GbmBuffer::~GbmBuffer()
+{
+    releaseBuffer();
+}
+
+void GbmBuffer::releaseBuffer()
 {
     if (m_bufferInterface) {
         clearBufferInterface();
     }
-    if (m_surface) {
+    if (m_surface && m_bo) {
         m_surface->releaseBuffer(m_bo);
     } else if (m_bo) {
         gbm_bo_destroy(m_bo);
     }
+    m_bo = nullptr;
 }
 
 void GbmBuffer::clearBufferInterface()
@@ -86,6 +92,11 @@ DrmGbmBuffer::~DrmGbmBuffer()
     }
 }
 
+void DrmGbmBuffer::releaseGbm()
+{
+    releaseBuffer();
+}
+
 void DrmGbmBuffer::initialize()
 {
     m_size = QSize(gbm_bo_get_width(m_bo), gbm_bo_get_height(m_bo));

src/plugins/platforms/drm/drm_buffer_gbm.h

@@ -38,6 +38,8 @@ public:
         return m_bo;
     }
 
+    void releaseBuffer();
+
 protected:
     QSharedPointer<GbmSurface> m_surface;
     gbm_bo *m_bo = nullptr;
@@ -61,6 +63,8 @@ public:
         }
     }
 
+    void releaseGbm() override;
+
     bool hasBo() const {
         return m_bo != nullptr;
     }

src/plugins/platforms/drm/drm_output.cpp

@@ -75,6 +75,24 @@ void DrmOutput::teardown()
     //this is needed so that the pageflipcallback handle isn't deleted
 }
 
+void DrmOutput::releaseGbm()
+{
+    if (auto buffer = m_crtc->current()) {
+        buffer->releaseGbm();
+    }
+    if (auto buffer = m_crtc->next()) {
+        buffer->releaseGbm();
+    }
+    if (m_primaryPlane) {
+        if (auto buffer = m_primaryPlane->current()) {
+            buffer->releaseGbm();
+        }
+        if (auto buffer = m_primaryPlane->next()) {
+            buffer->releaseGbm();
+        }
+    }
+}
+
 bool DrmOutput::hideCursor()
 {
     if (RenderLoopPrivate::get(m_renderLoop)->presentMode == RenderLoopPrivate::SyncMode::Adaptive

src/plugins/platforms/drm/drm_output.h

@@ -44,6 +44,7 @@ public:
 
     ///queues deleting the output after a page flip has completed.
     void teardown();
+    void releaseGbm();
     bool showCursor(DrmDumbBuffer *buffer);
     bool showCursor();
     bool hideCursor();

src/plugins/platforms/drm/egl_gbm_backend.cpp

@@ -71,9 +71,9 @@ void EglGbmBackend::cleanupOutput(Output &output)
 {
     cleanupFramebuffer(output);
 
-    output.buffer = nullptr;
-    output.secondaryBuffer = nullptr;
     if (output.eglSurface != EGL_NO_SURFACE) {
+        // gbm buffers have to be released before destroying the egl surface
+        output.output->releaseGbm();
         eglDestroySurface(eglDisplay(), output.eglSurface);
     }
 }
@@ -200,6 +200,8 @@ bool EglGbmBackend::resetOutput(Output &output, DrmOutput *drmOutput)
 
     // destroy previous surface
     if (output.eglSurface != EGL_NO_SURFACE) {
+        // gbm buffers have to be released before destroying the egl surface
+        output.output->releaseGbm();
         eglDestroySurface(eglDisplay(), output.eglSurface);
     }
     output.eglSurface = eglSurface;