Messages in this thread |  | | Subject | Re: [PATCH 1/2] list: Add list_is_null() to check if a list_head has been initialized | From | Sergei Shtylyov <> | Date | Sat, 27 Feb 2021 12:14:55 +0300 |
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Hello!
On 27.02.2021 1:49, Laurent Pinchart wrote:
> From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> > > The new function checks if the list_head prev and next pointers are > NULL, in order to see if a list_head that has been zeroed when allocated > has been initialized with INIT_LIST_HEAD() or added to a list.
So zeroed or initialized/added? :-)
> This can be used in cleanup functions that want to support being safely > called when an object has not been initialized, to return immediately. > In most cases other fields of the object can be checked for this > purpose, but in some cases a list_head field is the only option. > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> > --- > include/linux/list.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/linux/list.h b/include/linux/list.h > index 85c92555e31f..e4fc6954de3b 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -29,6 +29,19 @@ static inline void INIT_LIST_HEAD(struct list_head *list) > list->prev = list; > } > > +/** > + * list_is_null - check if a list_head has been initialized > + * @list: the list > + * > + * Check if the list_head prev and next pointers are NULL. This is useful to > + * see if a list_head that has been zeroed when allocated has been initialized > + * with INIT_LIST_HEAD() or added to a list.
So zeroed or initialized/added? :-)
> + */ > +static inline bool list_is_null(struct list_head *list) > +{ > + return list->prev == NULL && list->next == NULL;
Maybe instead:
return !list->prev && !list->next;
[...]
MBR, Sergei
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