glthread: mark internal bufferobjs for the ctx they belong to

this avoids unlimited unnecessary atomics

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36889>

src/mesa/main/glthread_bufferobj.c

@@ -25,6 +25,8 @@
 #include "dispatch.h"
 #include "main/bufferobj.h"
 
+#define PRIVATE_REFCOUNT 1000000
+
 /**
  * Create an upload buffer. This is called from the app thread, so everything
  * has to be thread-safe in the driver.
@@ -72,6 +74,11 @@ _mesa_glthread_release_upload_buffer(struct gl_context *ctx)
                    -glthread->upload_buffer_private_refcount);
       glthread->upload_buffer_private_refcount = 0;
    }
+   if (glthread->upload_buffer) {
+      glthread->upload_buffer->Ctx = NULL;
+      p_atomic_add(&glthread->upload_buffer->RefCount,
+                   -(PRIVATE_REFCOUNT - glthread->upload_buffer->CtxRefCount));
+   }
    _mesa_reference_buffer_object(ctx, &glthread->upload_buffer, NULL);
 }
 
@@ -142,6 +149,8 @@ _mesa_glthread_upload(struct gl_context *ctx, const void *data,
        */
       glthread->upload_buffer->RefCount += default_size;
       glthread->upload_buffer_private_refcount = default_size;
+      glthread->upload_buffer->Ctx = ctx;
+      glthread->upload_buffer->CtxRefCount = PRIVATE_REFCOUNT;
    }
 
    /* Upload data. */