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SubjectRe: [PATCH] memcg remove warning at DEBUG_VM=off
On Thu, 9 Apr 2009 22:25:12 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 8 Apr 2009 10:57:15 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-08 14:20:42]:
> >
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > This is against 2.6.30-rc1. (maybe no problem against mmotm.)
> > >
> > > ==
> > > Fix warning as
> > >
> > > CC mm/memcontrol.o
> > > mm/memcontrol.c:318: warning: ?$B!Fmem_cgroup_is_obsolete?$B!G defined but not used
> > >
> > > This is called only from VM_BUG_ON().
> > >
> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > ---
> > > Index: linux-2.6.30-rc1/mm/memcontrol.c
> > > ===================================================================
> > > --- linux-2.6.30-rc1.orig/mm/memcontrol.c
> > > +++ linux-2.6.30-rc1/mm/memcontrol.c
> > > @@ -314,13 +314,14 @@ static struct mem_cgroup *try_get_mem_cg
> > > return mem;
> > > }
> > >
> > > +#ifdef CONFIG_DEBUG_VM
> > > static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
> > > {
> > > if (!mem)
> > > return true;
> > > return css_is_removed(&mem->css);
> > > }
> > > -
> > > +#endif
> >
> > Can we change the code to use
> >
> > VM_BUG_ON(!mem || css_is_removed(&mem->css));
> >
>
> yup.
>
> --- a/mm/memcontrol.c~memcg-remove-warning-when-config_debug_vm=n-fix
> +++ a/mm/memcontrol.c
> @@ -314,14 +314,13 @@ static struct mem_cgroup *try_get_mem_cg
> return mem;
> }
>
> -#ifdef CONFIG_DEBUG_VM
> static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
> {
> if (!mem)
> return true;
> return css_is_removed(&mem->css);
> }
> -#endif
> +
>
> /*
> * Call callback function against all cgroup under hierarchy tree.
> @@ -933,7 +932,7 @@ static int __mem_cgroup_try_charge(struc
> if (unlikely(!mem))
> return 0;
>
> - VM_BUG_ON(mem_cgroup_is_obsolete(mem));
> + VM_BUG_ON(!mem || mem_cgroup_is_obsolete(mem));
>
> while (1) {
> int ret;
> _
>
> Although it really should be
>
> VM_BUG_ON(!mem);
> VM_BUG_ON(mem_cgroup_is_obsolete(mem));
>
> because if that BUG triggers, you'll be wondering which case caused it.
>
Ah, sorry, I missed the reply.
maybe calling css_is_removed() directly is a choice.
I'll prepare v2.

Regards,
-Kame



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