[virglrenderer-devel] [PATCH] renderer: return to original context before deleting a VA element

[ramin.azarmehr at gmail.com]

From: Ramin Azarmehr <ramin.azarmehr at gmail.com>

Bug (GL or GLES): deleting a VA element from a wrong current-context causes rendering/freezing problems.

Reason: at the time of deleting the VA element, the original context that generated it is not current, causing 
a "va->id" of another context to be deleted. This problem can also occur for sampler view/state and other objects. 

Fix: check if the correct EGL context is "current" (if not, switch to it) before deleting VAs. Calling
vrend_hw_switch_context() is cheap if the correct context is already current.

Reproducible example: run Android Nougat with virgl, then launch Google Maps (creates lots of VAs in its context). 
Then, press Square button of Android to tile the active applications (context switches to SurfaceFlinger), 
and close Google Maps window from there. The rendering will freeze (VA from SurfaceFlinger will be deleted instead). 
On Mesa-based drivers (e.g., Intel i915) an error like below will be generated by glBindVertexArray() 
in vrend_draw_bind_vertex_binding():

"Mesa: User error: GL_INVALID_OPERATION in glBindVertexArray(non-gen name)"

---
 src/vrend_renderer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/vrend_renderer.c b/src/vrend_renderer.c
index d6dee8b..85b68c1 100644
--- a/src/vrend_renderer.c
+++ b/src/vrend_renderer.c
@@ -252,6 +252,7 @@ struct vrend_vertex_element_array {
    unsigned count;
    struct vrend_vertex_element elements[PIPE_MAX_ATTRIBS];
    GLuint id;
+   struct vrend_context *ctx;
 };
 
 struct vrend_constants {
@@ -1276,6 +1277,7 @@ static void vrend_destroy_vertex_elements_object(void *obj_ptr)
    struct vrend_vertex_element_array *v = obj_ptr;
 
    if (vrend_state.have_gles31_vertex_attrib_binding) {
+      vrend_hw_switch_context(v->ctx, true);
       glDeleteVertexArrays(1, &v->id);
    }
    FREE(v);
@@ -1823,6 +1825,7 @@ int vrend_create_vertex_elements_state(struct vrend_context *ctx,
    if (!v)
       return ENOMEM;
 
+   v->ctx = ctx;
    v->count = num_elements;
    for (i = 0; i < num_elements; i++) {
       memcpy(&v->elements[i].base, &elements[i], sizeof(struct pipe_vertex_element));
-- 
2.17.1