ptrace improvement: PTRACE_O_INHERIT

[Roland McGrath]

> This is nontrivial to implement. We should obviously avoid the races with
> clone(). Now that cred_guard_mutex is per-process, this is probably possible...
> But I can't understand how we can check __ptrace_may_access() for each thread.
> We should refactor this code, task_lock() is needed to pin ->mm, and ->mm
> should be the same. Anyway, looks possible.

Right, that matches what I was thinking when I looked at it.
It seems like it should be doable, but looking at the details
of the locking got hairy fast.


Thanks,
Roland