On Thu, 12 Jul 2018 17:09:33 -0700 Omar Sandoval <osandov@xxxxxxxxxxx> wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> 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?
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)
