[PATCH v3 0/6] Freezer rewrite

[Peter Zijlstra]

Hi all,

This is the by now familiar rewrite of the freezer, but with yet another
attempt at getting the special blocked states (STOPPED/TRACED) right.

Currently it is already possible to tell if a task should be STOPPED from
looking at p->jobctl, the same idea is extended to TRACED and p->ptrace.

But treating p->jobctl/p->ptrace as canonical state, the blocked state can be
(hopefully correctly this time) reconstructed from it at all times.
Specifically, if a TRACED task was woken by the tracer, while the tracee was
FROZEN, the p->ptrace state will have been updated, and the thaw operation will
result in the wakeup.

Oleg, if you can please try and shoot holes in it again? :-)