[PATCH 0/2] wait/ptrace: assume __WALL if the child is traced

[Oleg Nesterov <oleg@redhat.com>]

Resend. And sorry for the huge delay. The patches are the same, I only
updated the changelog a little bit.

The previous discussion was a bit confusing, but iirc/iiuc nobody really
argued with this change. In particular strace/gdb maintainers do not think
it can break something.

To remind, 1 and 2 do not depend on each other. But if we decide to not
fix the kernel, then 2/2 makes much more sense. Most init's use waitid()
which doesn't allow __WALL, so the user-space fix will be more complicated
without this patch.

And just in case let me repeat that I agree, PTRACE_TRACEME is ugly. And
probably it should not succeed after re-parenting (in fact I personally
think PTRACE_TRACEME should not even exist). But imho it is too late to
try change this ancient interface, at least I strongly dislike the idea
to add something like is_global_init() check into ptrace_traceme(). And
any "sane" restriction here can break something too, plus this will
complicate the rules.

Oleg.