[Mesa-dev] [PATCH 1/6] st/mesa: fix sampler view context mismatch issue

[Brian Paul]

After a while of running google-chrome and viewing Bing maps, we'd see
"context mismatch in svga_sampler_view_destroy()" messages and
eventually crash because we leaked too many sampler views (the kernel
module would have too many sampler views).

When a texture object is being deleted, we call
st_texture_release_all_sampler_views() to release all the sampler
views.  In the list, there may sampler views which were created from
other contexts.

Previously, we called pipe_sampler_view_release(pipe, view) which would
use the given pipe context to destroy the view if the refcount hit
zero.  The svga error was triggered because we were calling
pipe->sampler_view_destroy(pipe, view) and the pipe context didn't
match the view's parent context.

Instead, call pipe_sampler_reference(&view, NULL).  That way, if
the refcount hits zero, we'll use the view's parent context to
destroy the view.  That's what we want.

The pipe_sampler_view_release() function was introduced years ago to
avoid freeing a sampler view with a context that was already deleted.

But since then we've improved sampler view and context tracking.
When a context is destroyed, the state tracker walks over all
texture objects and frees all sampler views which belong to that
context.  So, we should never end up deleting a sampler view after
its context is deleted.

After this, we can remove all calls to pipe_sampler_view_release()
in the drivers.

Finally, it appears that we need to implement a similar tear-down
mechanism for shaders and programs since we may generate per-context
shader variants.

Testing done: google chrome, misc GL demos, games
---
 src/mesa/state_tracker/st_context.c      | 3 +--
 src/mesa/state_tracker/st_sampler_view.c | 8 ++++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/mesa/state_tracker/st_context.c b/src/mesa/state_tracker/st_context.c
index 2898279..a7464fd 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -278,8 +278,7 @@ st_destroy_context_priv(struct st_context *st, bool destroy_pipe)
    st_destroy_bound_image_handles(st);
 
    for (i = 0; i < ARRAY_SIZE(st->state.frag_sampler_views); i++) {
-      pipe_sampler_view_release(st->pipe,
-                                &st->state.frag_sampler_views[i]);
+      pipe_sampler_view_reference(&st->state.frag_sampler_views[i], NULL);
    }
 
    /* free glReadPixels cache data */
diff --git a/src/mesa/state_tracker/st_sampler_view.c b/src/mesa/state_tracker/st_sampler_view.c
index e4eaf39..650a2b0 100644
--- a/src/mesa/state_tracker/st_sampler_view.c
+++ b/src/mesa/state_tracker/st_sampler_view.c
@@ -74,7 +74,7 @@ st_texture_set_sampler_view(struct st_context *st,
       if (sv->view) {
          /* check if the context matches */
          if (sv->view->context == st->pipe) {
-            pipe_sampler_view_release(st->pipe, &sv->view);
+            pipe_sampler_view_reference(&sv->view, NULL);
             goto found;
          }
       } else {
@@ -94,13 +94,13 @@ st_texture_set_sampler_view(struct st_context *st,
 
          if (new_max < views->max ||
              new_max > (UINT_MAX - sizeof(*views)) / sizeof(views->views[0])) {
-            pipe_sampler_view_release(st->pipe, &view);
+            pipe_sampler_view_reference(&view, NULL);
             goto out;
          }
 
          struct st_sampler_views *new_views = malloc(new_size);
          if (!new_views) {
-            pipe_sampler_view_release(st->pipe, &view);
+            pipe_sampler_view_reference(&view, NULL);
             goto out;
          }
 
@@ -225,7 +225,7 @@ st_texture_release_all_sampler_views(struct st_context *st,
    simple_mtx_lock(&stObj->validate_mutex);
    struct st_sampler_views *views = stObj->sampler_views;
    for (i = 0; i < views->count; ++i)
-      pipe_sampler_view_release(st->pipe, &views->views[i].view);
+      pipe_sampler_view_reference(&views->views[i].view, NULL);
    simple_mtx_unlock(&stObj->validate_mutex);
 }
 
-- 
1.8.5.6