If I understand correctly death_cookie was needed before
[PATCH] Embed struct utrace in task_struct - V2.
tracehook_report_death() could race with utrace_release_task() which
cleared -utrace, that is why tracehook_notify_death() had to read
task_utrace_struct() in advance and then pass this
I would rather not touch the tracehook interfaces now. You are indeed
right that the motivation for this had to do with the utrace-indirect code.
As I've said, I do intend to resurrect that code and send it upstream later
on. We can consider cleanups then. For now, let's not do anything
