Re: [patch 2/16] list_head debugging

[Andrew Morton <akpm@zip.com.au>]

Jan Harkes wrote:
> 
> On Sat, Jun 01, 2002 at 01:40:03AM -0700, Andrew Morton wrote:
> > The patch nulls out the dangling pointers so we get a nice oops at the
> > site of the buggy code.
> ...
> >  static __inline__ void list_del(struct list_head *entry)
> >  {
> >       __list_del(entry->prev, entry->next);
> > +     /*
> > +      * This is debug.  Remove it when the kernel has no bugs ;)
> > +      */
> > +     entry->next = 0;
> > +     entry->prev = 0;
> >  }
> 
> We've had this before, and it breaks some code that removes items from
> lists as follows,
> 
>     list_for_each(p, list)
>         if (condition)
>             list_del(p);

hmm.  I suppose that's sane.

> These would have to either use __list_del, or need to do,
> 
>     for(p = list.next; p != &list;) {
>         struct list_head *n = p->next;
>         if (condition)
>             list_del(p);
>         p = n;
>     }

list_for_each_safe() does this.