Rewrite async_exec_lock using mpscq
diff --git a/config.m4 b/config.m4
index 9ec7f49..67ce494 100644
--- a/config.m4
+++ b/config.m4
@@ -61,6 +61,7 @@
     src/core/lib/support/murmur_hash.c \
     src/core/lib/support/slice.c \
     src/core/lib/support/slice_buffer.c \
+    src/core/lib/support/stack_lockfree.c \
     src/core/lib/support/string.c \
     src/core/lib/support/string_posix.c \
     src/core/lib/support/string_util_win32.c \