ozone: ClientPixmapManager passes VGEM fd from browser to renderer.

ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc

Index: ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc
diff --git a/ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc b/ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc
index 76a94b89ad9f65b9fa74ae900072f02b7a85dc65..95b9333161ddf5ae2335ba708f80a07f899db290 100644
--- a/ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc
+++ b/ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.cc
@@ -4,12 +4,13 @@
 
 #include "ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.h"
 
-#include "base/file_descriptor_posix.h"
 #include "ui/gfx/native_pixmap_handle_ozone.h"
 #include "ui/ozone/public/client_native_pixmap_factory.h"
 
 #if defined(USE_VGEM_MAP)
 #include <fcntl.h>
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/platform_thread.h"
 #include "ui/ozone/platform/drm/gpu/client_native_pixmap_vgem.h"
 #endif
 
@@ -32,18 +33,29 @@ class ClientNativePixmapGbm : public ClientNativePixmap {
 
 class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
  public:
-  ClientNativePixmapFactoryGbm() {
+  ClientNativePixmapFactoryGbm() : set_vgem_fd_event_(true, false) {}
+  ~ClientNativePixmapFactoryGbm() override {}
+
+  // Overridden from ClientNativePixmapFactory:
+  scoped_ptr<base::ScopedFD> OpenVgemFD() const override {
 #if defined(USE_VGEM_MAP)
-    // TODO(dshwang): remove ad-hoc file open. crrev.com/1248713002
     static const char kVgemPath[] = "/dev/dri/renderD129";
     int vgem_fd = open(kVgemPath, O_RDWR | O_CLOEXEC);
-    vgem_fd_.reset(vgem_fd);
-    DCHECK_GE(vgem_fd_.get(), 0) << "Failed to open: " << kVgemPath;
+    DCHECK_GE(vgem_fd, 0) << "Failed to open: " << kVgemPath;
+    return make_scoped_ptr(new base::ScopedFD(vgem_fd));
+#endif
+    return nullptr;
+  }
+  void SetVgemFD(scoped_ptr<base::ScopedFD> vgem_fd) override {
+#if defined(USE_VGEM_MAP)
+    DCHECK_LT(vgem_fd_.get(), 0);
+    vgem_fd_ = vgem_fd->Pass();
+#ifndef NDEBUG
+    set_vgem_fd_thread_id_ = base::PlatformThread::CurrentRef();
+#endif
+    set_vgem_fd_event_.Signal();
 #endif
   }
-  ~ClientNativePixmapFactoryGbm() override {}
-
-  // ClientNativePixmapFactory:
   std::vector<Configuration> GetSupportedConfigurations() const override {
     const Configuration kConfigurations[] = {
         {gfx::BufferFormat::BGRA_8888, gfx::BufferUsage::SCANOUT},
@@ -65,6 +77,13 @@ class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
     switch (usage) {
       case gfx::BufferUsage::MAP:
 #if defined(USE_VGEM_MAP)
+        // A valid |vgem_fd_| is required to acquire a VGEM bo. This will wait
+        // for a valid |vgem_fd_| if one has not yet been set.
+        set_vgem_fd_event_.Wait();
+#ifndef NDEBUG
+        DCHECK(!(set_vgem_fd_thread_id_ == base::PlatformThread::CurrentRef()));
+#endif
+        DCHECK_GE(vgem_fd_.get(), 0);
         return ClientNativePixmapVgem::ImportFromDmabuf(
             vgem_fd_.get(), scoped_fd.get(), size, handle.stride);
 #endif
@@ -84,6 +103,10 @@ class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
  private:
 #if defined(USE_VGEM_MAP)
   base::ScopedFD vgem_fd_;
+#ifndef NDEBUG
+  base::PlatformThreadRef set_vgem_fd_thread_id_;

[spang, 2015/08/17 19:04:33]

Can you use base::ThreadChecker for this?

[reveman, 2015/08/17 19:09:52]

I'm afraid not as we don't know what a valid thread is. All we know is that
Wait() should not be called on the same thread that the fd was set on.

[spang, 2015/08/17 19:17:29]

Ah, I see.

We should use DCHECK_IS_ON() instead of !NDEBUG so that DCHECK_ALWAYS_ON enables
these assertions.

[reveman, 2015/08/18 08:47:34]

sure but if we change this to DCHECK_IS_ON(), please change
ChildIOSurfaceManager too.

[dshwang, 2015/08/18 14:14:39]

ThreadChecker is better, because it's just wrapper of PlatformThreadRef
I replace it with ThreadChecker here as well as ChildIOSurfaceManager
As replacing it with ThreadChecker, macro isn't needed anymore because
ThreadChecker has the macro internally.

+#endif
+  base::WaitableEvent set_vgem_fd_event_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ClientNativePixmapFactoryGbm);