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Date: Sun, 29 Sep 2002 10:33:15 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Zach Brown <zab@zabbo.net>
Cc: Linus Torvalds <torvalds@transmeta.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] 2.5.39 list_head debugging
In-Reply-To: <20020929015852.K13817@bitchcake.off.net>
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> 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

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