Switch to using a CAS loop to update the token value.
diff --git a/grpc.gemspec b/grpc.gemspec
index 1ca2446..95aba00 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -97,6 +97,7 @@
s.files += %w( src/core/lib/profiling/basic_timers.c )
s.files += %w( src/core/lib/profiling/stap_timers.c )
s.files += %w( src/core/lib/support/alloc.c )
+ s.files += %w( src/core/lib/support/atm.c )
s.files += %w( src/core/lib/support/avl.c )
s.files += %w( src/core/lib/support/backoff.c )
s.files += %w( src/core/lib/support/cmdline.c )