The code he pointed to is for kernel 2.6.18 which at this point could be considered ancient history. If you look at current master - https://git.kernel.org/cgit

The code he pointed to is for kernel 2.6.18 which at this point could be considered ancient history. If you look at current master - https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c?id=refs/tags/v3.15-rc1#n1365 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.... it looks like it has been re-factored somewhat, although the lock is still in there.