[Mesa-dev] [PATCH 05/13] meta: Save and restore the framebuffer using gl_framebuffer instead of GL API object handle

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Some meta operations can be called recursively.  Future changes (the
"Don't pollute the ... namespace" changes) will cause objects with
invalid names to be used.  If a nested meta operation tries to restore
an object named 0xDEADBEEF, it will fail.

This also fixes another latent bug in meta.  In a multithreaded,
multicontext application, one thread can delete an object that is bound
in another thread.  That object continues to exist until it is unbound
(i.e., its refcount drops to zero).  Meta unbinds objects all over the
place.  As a result, the rebind in _mesa_meta_end could fail because the
object vanished!

See https://bugs.freedesktop.org/show_bug.cgi?id=92363#c8.

Using _mesa_reference_<object type> to save and restore the objects
prevents the refcount from going to zero.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92363
---
 src/mesa/drivers/common/meta.c | 13 ++++++-------
 src/mesa/drivers/common/meta.h |  3 ++-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index c99a220..1222c9b 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -48,6 +48,7 @@
 #include "main/feedback.h"
 #include "main/formats.h"
 #include "main/format_unpack.h"
+#include "main/framebuffer.h"
 #include "main/glformats.h"
 #include "main/image.h"
 #include "main/macros.h"
@@ -825,8 +826,8 @@ _mesa_meta_begin(struct gl_context *ctx, GLbitfield state)
       if (ctx->RasterDiscard)
          _mesa_set_enable(ctx, GL_RASTERIZER_DISCARD, GL_FALSE);
 
-      save->DrawBufferName = ctx->DrawBuffer->Name;
-      save->ReadBufferName = ctx->ReadBuffer->Name;
+      _mesa_reference_framebuffer(&save->DrawBuffer, ctx->DrawBuffer);
+      _mesa_reference_framebuffer(&save->ReadBuffer, ctx->ReadBuffer);
    }
 }
 
@@ -1212,11 +1213,9 @@ _mesa_meta_end(struct gl_context *ctx)
    if (save->TransformFeedbackNeedsResume)
       _mesa_ResumeTransformFeedback();
 
-   if (ctx->DrawBuffer->Name != save->DrawBufferName)
-      _mesa_BindFramebuffer(GL_DRAW_FRAMEBUFFER, save->DrawBufferName);
-
-   if (ctx->ReadBuffer->Name != save->ReadBufferName)
-      _mesa_BindFramebuffer(GL_READ_FRAMEBUFFER, save->ReadBufferName);
+   _mesa_bind_framebuffers(ctx, save->DrawBuffer, save->ReadBuffer);
+   _mesa_reference_framebuffer(&save->DrawBuffer, NULL);
+   _mesa_reference_framebuffer(&save->ReadBuffer, NULL);
 
    if (state & MESA_META_DRAW_BUFFERS) {
       _mesa_drawbuffers(ctx, ctx->DrawBuffer, ctx->Const.MaxDrawBuffers,
diff --git a/src/mesa/drivers/common/meta.h b/src/mesa/drivers/common/meta.h
index ee92035..03d86c8 100644
--- a/src/mesa/drivers/common/meta.h
+++ b/src/mesa/drivers/common/meta.h
@@ -186,7 +186,8 @@ struct save_state
    GLboolean RasterDiscard;
    GLboolean TransformFeedbackNeedsResume;
 
-   GLuint DrawBufferName, ReadBufferName;
+   struct gl_framebuffer *DrawBuffer;
+   struct gl_framebuffer *ReadBuffer;
 
    /** MESA_META_DRAW_BUFFERS */
    GLenum ColorDrawBuffers[MAX_DRAW_BUFFERS];
-- 
2.5.0