pytorch

a94f9c72 - Fix race condition in Function::optimized_graph(). (#27323)

Fix race condition in Function::optimized_graph(). (#27323) The current logic is buggy, and will fail in the following situation: Thread A: check optimized_graph_, it is empty. Thread A: claim the mutex in order to initialize optimized_graph_. Thread A: copy graph_ into optimized_graph_. Thread A: start running optimizations on optimized_graph_. Thread B: check optimized_graph_, it is not empty. Thread B: start using optimized_graph_. BUG: Thread B is using the graph while it's still being mutated by Thread A. [ghstack-poisoned]