til: introduce til_module_render_limited() variant

With the introduction of discoverable on-stream contexts, with
the intention of modules finding them at runtime for nested
rendering, relying exclusively on limiting n_cpus @
til_module_create_context() is no longer adequate.

When the nested rendering makes use of a context created
elsewhere, it can't make any assumptions about what its n_cpus
is, nor should it be attempting to change that value for its use.

So this variant just adds a max_cpus parameter for setting an
upper bound to whatever is found in the context's n_cpus.

The impetus for this is to fix the ref builtin, which you can
currently trick into deadlock by performing a nested threaded
render within a threaded render.  What the ref module should be
doing is propagating its own context's n_cpus down as the upper
bound, via this new render variant.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/til.h b/src/til.h
index eea8009..ec078db 100644
--- a/src/til.h
+++ b/src/til.h
@@ -45,6 +45,7 @@ const til_module_t * til_lookup_module(const char *name);
 void til_get_modules(const til_module_t ***res_modules, size_t *res_n_modules);
 char * til_get_module_names(unsigned flags_excluded, const char **exclusions);
 void til_module_render(til_module_context_t *context, til_stream_t *stream, unsigned ticks, til_fb_fragment_t **fragment_ptr);
+void til_module_render_limited(til_module_context_t *context, til_stream_t *stream, unsigned ticks, unsigned max_cpus, til_fb_fragment_t **fragment_ptr);
 int til_module_create_contexts(const til_module_t *module, til_stream_t *stream, unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup, size_t n_contexts, til_module_context_t **res_contexts);
 int til_module_create_context(const til_module_t *module, til_stream_t *stream, unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup, til_module_context_t **res_context);
 til_module_context_t * til_module_destroy_context(til_module_context_t *context, til_stream_t *stream);