Messages in this thread | | | Date | Thu, 25 Aug 2011 23:52:03 +0200 | From | Tejun Heo <> | Subject | Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable |
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Hello, Oleg.
On Thu, Aug 25, 2011 at 06:56:50PM +0200, Oleg Nesterov wrote: > 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.
Hmmm... yeah, maybe moving it right after setting ->state would be safer. Care to send a patch?
> But since we can't see the threads after exit_notify (in general), > the current ->exit_state check looks reasonable.
I prefer setting NOFREEZE after point of no return from exit path. The intention is clearer that way, I think.
> > Another freezer user is the cgroup, > > Yes. And I don't understand this case too. I mean, the fact we ignore > the exiting tasks.
Because it's basically a mass (or meta) job control mechanism and it's nicer to be able to kill processes after freezing berserk cgroups.
Thanks.
-- tejun
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