Re: [Xen-devel] [PATCH 09/18] xen/arm: Add rcu_barrier() before enabling non-boot CPUs on resume

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 14 Nov 2018, Julien Grall wrote:
> Hi,
> 
> On 12/11/2018 11:30, Mirela Simonovic wrote:
> > The rcu_barrier() has to be added to ensure that the per cpu area is
> > freed before a non-boot CPU tries to initialize it (_free_percpu_area()
> > has to be called before the init_percpu_area()). This scenario occurs
> > when non-boot CPUs are hot-unplugged on suspend and hotplugged on resume.
> 
> From the description, this is a bug introduced by the previous patch. So
> should merged in it.
 
It makes sense to squash this patch together with patch #8.


> The commit message will also need to explain why the rcu_barrier() is
> required.
>
> > Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> > Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
> > ---
> >   xen/arch/arm/suspend.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/xen/arch/arm/suspend.c b/xen/arch/arm/suspend.c
> > index dae1b1f7d6..8e8e531d61 100644
> > --- a/xen/arch/arm/suspend.c
> > +++ b/xen/arch/arm/suspend.c
> > @@ -133,6 +133,7 @@ static long system_suspend(void *data)
> >       system_state = SYS_STATE_resume;
> >     resume_nonboot_cpus:
> > +    rcu_barrier();
> >       enable_nonboot_cpus();
> >       thaw_domains();
> >       system_state = SYS_STATE_active;
> > 
> 
> -- 
> Julien Grall
> 

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