Re: [RFC] Fix SMP brokenness for PF_FREEZE and make freezing usable for other purposes

Pavel Machek
2005-07-03T11:06:39Z

Hi!

> > > - freeze(p);
> > > + set_thread_flag(TIF_FREEZE);
> >
> > Shouldn't that be "set_ti_thread_flag(p->thread_info, TIF_FREEZE)"?
> > Otherwise you freeze current, not the thread "p".
>
> Correct. Which also means that we have not progressed yet beyond an
> academic version of the patch:
>
> ---
>
> Revise handling of freezing in the suspend code
>
> The current suspend code modifies thread flags from outside the context of process.
> This creates a SMP race.
>
> The patch fixes that by introducing a TIF_FREEZE flag (for all arches). Also
>
> - Uses a completion handler instead of waiting in a schedule loop in the refrigerator.
>
> - Introduces a semaphore freezer_sem to provide a way that multiple kernel
> subsystems can use the freezing ability without interfering with one another.
>
> - Include necessary definitions for the migration code if CONFIG_MIGRATE is set.
>
> - Removes PF_FREEZE
>
> Signed-off-by: Christoph Lameter <christoph@lameter.com>

This patch breaks suspend for me (first suspend works, second suspend
fails to freeze processes). [I was offline, that's why it took so
long.]

I see patches 1/2 and 2/2 submitted; if you still feel I should apply
some of them, tell me.
Pavel

--
teflon -- maybe it is a trademark, but it should not be.