Re: [PATCH] 2.5.39 list_head debugging

[Ingo Molnar]

> This patch adds some straight-forward assertions that check the
> validity of arguments to the list_* inlines. [...]

+	BUG_ON(list == NULL);
+	BUG_ON(list->next == NULL);
+	BUG_ON(list->prev == NULL);

these checks are not needed - they'll trivially be oopsing when trying to
use them, right?

+	BUG_ON(list->next->prev != list);
+	BUG_ON(list->prev->next != list);

these two are indeed nice to have.

+	BUG_ON((list->next == list) && (list->prev != list));
+	BUG_ON((list->prev == list) && (list->next != list));

arent these redundant? If list->next->prev == list and list->prev->next ==
list, then if list->next == list then list->prev == list. Ditto for the 
other rule.

so i think we only need the following two checks:

+	BUG_ON(list->next->prev != list);
+	BUG_ON(list->prev->next != list);

and we could as well add these unconditionally (no .config complexity
needed), until 2.6.0 or so, hm?

	Ingo