Messages in this thread | | | Date | Sun, 18 Feb 2007 14:31:24 +0300 | From | Oleg Nesterov <> | Subject | Re: [RFC PATCH(Experimental) 0/4] Freezer based Cpu-hotplug |
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On 02/18, Rafael J. Wysocki wrote: > > On Sunday, 18 February 2007 00:47, Oleg Nesterov wrote: > > > > However, this means that sys_vfork() makes impossible to freeze processes > > until child exits/execs. Not good. > > Yes, but this also is the current behavior.
Yes, yes, I see.
I forgot to say that we have another problem: coredumping.
A thread which does do_coredump() send SIGKILL to ->mm users, and sleeps on ->mm->core_startup_done. Now it can't be frozen if sub-thread goes to refrigerator. I think this could be solved easily if we add a check to refrigerator() as you suggested for ->vfork_donw.
> I think the real solution would be to use an interruptible completion in the > vfork code. It was discussed some time ago and, IIRC, Ingo had an experimental > patch that implemented it. Still, for the suspend this really is not an issue > in practice, so it wasn't merged.
It is not (afaics) so trivial to do rightly, and with this change the parent will be seen as TASK_INTERRUPTIBLE even without freezer in progress.
A very vague idea: what if parent will do
current->flags |= PF_PLEASE_CONSIDER_ME_AS_FROZEN_BUT_SET_TIF_FREEZE wait_for_completion(&vfork); try_to_freeze();
?
> It may be a good time to solve this problem now. :-)
Yes, I think so :)
Oleg.
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