Messages in this thread | | | Date | Thu, 25 Aug 2011 18:56:50 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable |
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On 08/25, Tejun Heo wrote: > > Yeah, what 'freeze' should do is a bit vague on the edges, I think. > The freezer can't really halt the whole system operation including > IOs. Tasks aren't the only source which can kick those off. There > are other asynchronous sources,
Of course.
But still I can't understand why it is better to consider the exiting task as "frozen" from the very beginning, right after PTRACE_EVENT_EXIT. do_exit() does a lot of misc things, and this patch simply makes it "invisible" to the freezer. This looks "unsafe" even if this is fine for suspend/etc.
To me, try_to_freeze_tasks() should succed when all threads either sleep in refrigerator(), or ->state = TASK_DEAD (the final schedule() was called). Until then try_to_freeze_tasks() should retry.
But since we can't see the threads after exit_notify (in general), the current ->exit_state check looks reasonable.
But again, again, I won't argue.
> Rafael, can you please enlighten > us on the subject?
Please ;)
> Another freezer user is the cgroup,
Yes. And I don't understand this case too. I mean, the fact we ignore the exiting tasks.
Oleg.
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