Re: freezer problems

From: Oleg Nesterov
Date: Sun Feb 18 2007 - 11:17:36 EST

On 02/18, Rafael J. Wysocki wrote:
> On Sunday, 18 February 2007 15:52, Oleg Nesterov wrote:
> >
> > And now another problem: exec. de_thread() sleeps in TASK_UNINTERRUPTIBLE
> > waiting for all sub-threads to die, and we have the same "deadlock" if
> > one of them is frozen. This is nasty. Probably we can change the ->state
> > to TASK_INTERRUPTIBLE and add try_to_freeze(), or play with the new PF_
> > flag, but I am not sure it is safe to freeze() the task which is deep
> > in the exec() path.
> Hm, I haven't been aware of this case.
> Well, probably we can do something like in the patch that I've just sent: the
> child that enters the refrigerator should know that the parent is
> uninterruptible and will wait for it to exit. Thus it can either mark the
> parent as frozen or just exit the refrigerator without freezing itself.

Sub-thread could already sleep in refrigerator when another thread does exec.
So we have no choice but somehow freeze the execer. But again, I don't know
if it is safe to freeze it here, at de_thread() stage. It is called from
load_xxx_binary(), we may hold some important locks...


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