Brian,
One question also for my own education inline below:
On Friday, 8 March 2019 23:52:09 CET Brian Paul wrote:
> 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.
That sounds plausible so far.
What I wonder, is calling into an 'arbitrary' different context and do work
there
thread safe for any gallium driver?
Especially since pipe_sampler_view_reference in its documentation says that the
views provided need to originate from the same context and that this must
be the 'current'.
I have been taking a quick look into iris and radeonsi and both seem to be safe
in terms of threads for dereferencing the views finally.
But either the documentation of pipe_sampler_view_reference should be updated
or I may miss an other piece of the puzzle to see that it is still save to do
so.
Can you tell me?
thanks
Mathias
>
> 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);
> }
>
>
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