Re: [PATCH] padata: use smp_mb in padata_reorder to avoid orphaned padata jobs

[Steffen Klassert]

On Fri, Jul 12, 2019 at 06:06:36PM +0800, Herbert Xu wrote:
> Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> wrote:
> >
> > CPU0                                 CPU1
> > 
> > padata_reorder                       padata_do_serial
> >  LOAD reorder_objects  // 0
> >                                       INC reorder_objects  // 1
> >                                       padata_reorder
> >                                         TRYLOCK pd->lock   // failed
> >  UNLOCK pd->lock
> 
> I think this can't happen because CPU1 won't call padata_reorder
> at all as it's the wrong CPU so it gets pushed back onto a work
> queue which will go back to CPU0.
> 
> Steffen, could you please take a look at this as there clearly
> is a problem here?

I'm currently travelling, will have a look at it when I'm back.