From f775e13c6ee9a84028473c401b15ec5703e2fbca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Fri, 24 Apr 2015 10:23:06 +0200
Subject: [PATCH] Improve tracking of DrmBuffers in DrmBackend

We need to prevent double deletions from the gbm callback. Therefore
we track all buffers in DrmBackend and pass the DrmBackend as user
data.
---
 drm_backend.cpp | 26 +++++++++++++++++++++-----
 drm_backend.h   |  8 ++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/drm_backend.cpp b/drm_backend.cpp
index c874f82c0d..b6f6c6f0d1 100644
--- a/drm_backend.cpp
+++ b/drm_backend.cpp
@@ -481,16 +481,25 @@ OpenGLBackend *DrmBackend::createOpenGLBackend()
 
 DrmBuffer *DrmBackend::createBuffer(const QSize &size)
 {
-    return new DrmBuffer(this, size);
+    DrmBuffer *b = new DrmBuffer(this, size);
+    m_buffers << b;
+    return b;
 }
 
 DrmBuffer *DrmBackend::createBuffer(gbm_surface *surface)
 {
 #if HAVE_GBM
-    return new DrmBuffer(this, surface);
+    DrmBuffer *b = new DrmBuffer(this, surface);
+    m_buffers << b;
+    return b;
 #endif
 }
 
+void DrmBackend::bufferDestroyed(DrmBuffer *b)
+{
+    m_buffers.removeAll(b);
+}
+
 DrmOutput::DrmOutput(DrmBackend *backend)
     : m_backend(backend)
 {
@@ -633,8 +642,14 @@ DrmBuffer::DrmBuffer(DrmBackend *backend, const QSize &size)
 #if HAVE_GBM
 static void gbmCallback(gbm_bo *bo, void *data)
 {
-    Q_UNUSED(bo);
-    delete reinterpret_cast<DrmBuffer*>(data);
+    DrmBackend *backend = reinterpret_cast<DrmBackend*>(data);
+    const auto &buffers = backend->buffers();
+    for (auto buffer: buffers) {
+        if (buffer->gbm() == bo) {
+            delete buffer;
+            return;
+        }
+    }
 }
 #endif
 
@@ -653,12 +668,13 @@ DrmBuffer::DrmBuffer(DrmBackend *backend, gbm_surface *surface)
     if (drmModeAddFB(m_backend->fd(), m_size.width(), m_size.height(), 24, 32, m_stride, gbm_bo_get_handle(m_bo).u32, &m_bufferId) != 0) {
         qWarning(KWIN_CORE) << "drmModeAddFB failed";
     }
-    gbm_bo_set_user_data(m_bo, this, gbmCallback);
+    gbm_bo_set_user_data(m_bo, m_backend, gbmCallback);
 #endif
 }
 
 DrmBuffer::~DrmBuffer()
 {
+    m_backend->bufferDestroyed(this);
     delete m_image;
     if (m_memory) {
         munmap(m_memory, m_bufferSize);
diff --git a/drm_backend.h b/drm_backend.h
index eb4ddcfc30..2da5268274 100644
--- a/drm_backend.h
+++ b/drm_backend.h
@@ -62,6 +62,10 @@ public:
     QVector<DrmOutput*> outputs() const {
         return m_outputs;
     }
+    QVector<DrmBuffer*> buffers() const {
+        return m_buffers;
+    }
+    void bufferDestroyed(DrmBuffer *b);
 
 Q_SIGNALS:
     void screensQueried();
@@ -92,6 +96,7 @@ private:
     int m_cursorIndex = 0;
     int m_pageFlipsPending = 0;
     bool m_active = false;
+    QVector<DrmBuffer*> m_buffers;
 };
 
 class DrmOutput
@@ -153,6 +158,9 @@ public:
     quint32 stride() const {
         return m_stride;
     }
+    gbm_bo *gbm() const {
+        return m_bo;
+    }
     void releaseGbm();
 
 private: