Forbid DeepEP racing condition when too many tokens (#9567)

python/sglang/srt/layers/moe/token_dispatcher/deepep.py

@@ -272,6 +272,9 @@ class _DeepEPDispatcherImplBase:
         self.num_max_dispatch_tokens_per_rank = get_int_env_var(
             "SGLANG_DEEPEP_NUM_MAX_DISPATCH_TOKENS_PER_RANK", 128
         )
+        # DeepEP internode_ll dispatch uses FINISHED_SUM_TAG=1024
+        # and the logic requires num-tokens-sent-from-one-rank-to-another-rank less than it
+        assert self.num_max_dispatch_tokens_per_rank <= 1024
 
         self.handle = None