Re: [RFC][PATCH] lru_add_drain_all() don't use schedule_on_each_cpu()

Nick Piggin
2008-10-24T04:55:59Z

On Fri, Oct 24, 2008 at 01:54:46PM +0900, KOSAKI Motohiro wrote:
> > >
> > > Actually, schedule_on_each_cpu() is very problematic function.
> > > it introduce the dependency of all worker on keventd_wq,
> > > but we can't know what lock held by worker in kevend_wq because
> > > keventd_wq is widely used out of kernel drivers too.
> > >
> > > So, the task of any lock held shouldn't wait on keventd_wq.
> > > Its task should use own special purpose work queue.
> >
> > I don't see a better way to solve it, other than avoiding lru_add_drain_all
>
> Well,
>
> Unfortunately, lru_add_drain_all is also used some other VM place
> (page migration and memory hotplug).
> and page migration's usage is the same of this mlock usage.
> (1. grab mmap_sem 2. call lru_add_drain_all)
>
> Then, change mlock usage isn't solution ;-)

No, not mlock alone.