The possible future improvement that Linus mentions here: For example, the per-VM memory management semaphore could very usefully be a blocking read-write

The possible future improvement that Linus mentions here: For example, the per-VM memory management semaphore could very usefully be a blocking read-write lock, but without heavy thread contention a mutex semaphore is basically equivalent. has actually come to pass: the mm_struct is now protected by struct rw_semaphore mmap_sem.