On Sunday, 25 February 2007 21:31, Oleg Nesterov wrote:
> On 02/25, Rafael J. Wysocki wrote:
> >
> > On Sunday, 25 February 2007 16:40, Aneesh Kumar wrote:
> > > On 2/25/07, Aneesh Kumar <[email protected]> wrote:
> > > > On 2/25/07, Rafael J. Wysocki <[email protected]> wrote:
> > > > > On Sunday, 25 February 2007 15:33, Aneesh Kumar wrote:
> > > > > > On 2/25/07, Rafael J. Wysocki <[email protected]> wrote:
> > [--snip--]
> > >
> > > Thinking about this i guess we have a problem with the above approach
> > > i outlined. if we have one task that is waiting on the event and more
> > > than one that can generate the event then the above logic would not
> > > work. Also with cases other than vfork; logic of tracking the waiting
> > > task gets complex. I guess what we have right now is better.
> >
> > I assume by "righ now" you mean the latest version of my patch. ;-)
> >
> > Still, having pondered the Pavel's suggestion for a while I think it's doable
> > without the addtitional process flag. Patch below.
>
> Probably I missed something, (I didn't see this patch and I missed the
> start of discussion), but I can't understand this patch.
Please see http://lkml.org/lkml/2007/2/25/53 .
> > +__wait_for_completion(struct completion *x, int freezable)
> > {
> > might_sleep();
> >
> > @@ -3817,6 +3818,9 @@ void fastcall __sched wait_for_completio
> > __set_current_state(TASK_UNINTERRUPTIBLE);
> > spin_unlock_irq(&x->wait.lock);
> > schedule();
> > + if (freezable)
> > + try_to_freeze();
> > +
> > spin_lock_irq(&x->wait.lock);
> > } while (!x->done);
> > __remove_wait_queue(&x->wait, &wait);
> > @@ -3824,7 +3828,7 @@ void fastcall __sched wait_for_completio
> > x->done--;
> > spin_unlock_irq(&x->wait.lock);
> > }
> >
> > ..........
> >
> > @@ -48,6 +48,9 @@ void refrigerator(void)
> > task_unlock(current);
> > return;
> > }
> > + if (current->vfork_done)
> > + wake_up_process(current->parent);
> > +
>
> What if current->parent doesn't have TIF_FREEZE yet? ->parent will schedule()
> again, child goes to refrigerator. Now, how can we freeze the ->parent?
Good point. I didn't think about it.
All in all, having tried some different approaches I think that the patch at
http://lkml.org/lkml/2007/2/25/80 is the right thing to do.
Pavel, do you agree?
Rafael
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