On Tue, Jul 17, 2018 at 07:35:04PM -0700, Andrew Morton wrote:
> On Thu, 12 Jul 2018 17:09:33 -0700 Omar Sandoval <osan...@osandov.com> wrote:
>
> > From: Omar Sandoval <osan...@fb.com>
> >
> > kclist_add() is only called at init time, so there's no point in
> > grabbing any locks. We're also going to replace the rwlock with a rwsem,
> > which we don't want to try grabbing during early boot.
> >
> > ...
> >
> > --- a/fs/proc/kcore.c
> > +++ b/fs/proc/kcore.c
> > @@ -62,6 +62,7 @@ static LIST_HEAD(kclist_head);
> > static DEFINE_RWLOCK(kclist_lock);
> > static int kcore_need_update = 1;
> >
> > +/* This doesn't grab kclist_lock, so it should only be used at init time.
> > */
> > void
> > kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
> > {
> > @@ -69,9 +70,7 @@ kclist_add(struct kcore_list *new, void *addr, size_t
> > size, int type)
> > new->size = size;
> > new->type = type;
> >
> > - write_lock(&kclist_lock);
> > list_add_tail(&new->list, &kclist_head);
> > - write_unlock(&kclist_lock);
> > }
>
> So we can mark kclist_add() as __init, yes?
Yes, thanks, I'll add that in v2.
> That way we save a scrap of ram and if someone starts calling
> kclist_add() from non-__init code we get a build-time warning.
>
> --- a/fs/proc/kcore.c~proc-kcore-dont-grab-lock-for-kclist_add-fix
> +++ a/fs/proc/kcore.c
> @@ -63,7 +63,7 @@ static DEFINE_RWLOCK(kclist_lock);
> static int kcore_need_update = 1;
>
> /* This doesn't grab kclist_lock, so it should only be used at init time. */
> -void
> +void __init
> kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
> {
> new->addr = (unsigned long)addr;
> --- a/include/linux/kcore.h~proc-kcore-dont-grab-lock-for-kclist_add-fix
> +++ a/include/linux/kcore.h
> @@ -35,7 +35,7 @@ struct vmcoredd_node {
> };
>
> #ifdef CONFIG_PROC_KCORE
> -extern void kclist_add(struct kcore_list *, void *, size_t, int type);
> +extern void __init kclist_add(struct kcore_list *, void *, size_t, int type);
> #else
> static inline
> void kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
>
>
