Sharing page tables with msharefs

> That raises an obvious question, he said: why not just use threads? The answer was that "mmap_lock sucks". It is also not possible to change the existing behavior of MAP_SHARED, since that would break programs, so there would need to be, at a minimum, a new mmap() flag if not a new system call. Aziz said that the separate system call makes the page-table sharing explicit rather than it just being a side effect. That makes the decision to opt into this behavior explicit as well.

https://lwn.net/Articles/895217/