Do not mess with the GC. There shouldn't be a race condition here.

If the function is called manually, the variable is referenced from the stack.
If the function is called called as finalizer, the GC will make sure it is not called twice.

src/GZip.jl

@@ -299,17 +299,10 @@ gzdopen(s::IOStream, args...) = gzdopen(fd(s), args...)
 fd(s::GZipStream) = error("fd is not supported for GZipStreams")
 
 function close(s::GZipStream)
-
-    # The garbage collector needs to be temporarily disabled because of a possible
-    # race condition if it runs between testing and setting s._closed
-
-    gc_enable(false)
     if s._closed
-        gc_enable(true)
         return Z_STREAM_ERROR
     end
     s._closed = true
-    gc_enable(true)
 
     s.name *= " (closed)"