Re: [PATCH] prctl: add PR_{GET,SET}_KILL_DESCENDANTS_ON_EXIT

Hi Oleg,

Thanks for the review.

On Thu, 2018-11-29 at 13:34 +0100, Oleg Nesterov wrote:

To me it would be more clean to call walk_process_tree(kill_descendant_visitor)
unconditionally in find_new_reaper() right before "if (has_child_subreaper)", but
then we will need to shift read_lock(tasklist) from walk_process_tree().

Yes, that's the reason why I added the call before the tasklist lock.
Let me know if you want me to move the read lock from
walk_process_tree() to PR_SET_CHILD_SUBREAPER (the only caller)
instead.

So I think the patch is mostly fine, the only problem I can see is that
PR_SET_KILL_DESCENDANTS_ON_EXIT can race with PR_SET_CHILD_SUBREAPER, they both
need to update the bits in the same word.

Good point. I'll make it a regular bool instead of a bitfield for v2,
unless you have another approach in mind to fix this.

Jürg