Comment 2 for bug 103133

This doesn't seem to be a bug. From strace(1), -f option:

                   If the parent process decides to wait(2) for a child
                   that is currently being traced, it is suspended
                   until an appropriate child process either terminates
                   or incurs a signal that would cause it to terminate
                   (as determined from the child’s current signal dis‐
                   position).

of course, if that child happens to be strace itself, the "until" bit probably ceases to apply.

I'm guessing the call to proc.communicate() involves wait()ing.

(Closing bug for now; if further information arises that suggests that this may still be a bug, please feel free to reopen.)