From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: BUG_ON in remap_pte_range: Why? From: Ed L Cashin Date: Wed, 21 May 2003 00:20:32 -0400 In-Reply-To: <20030520202728.42626.qmail@web12308.mail.yahoo.com> (Ravi's message of "Tue, 20 May 2003 13:27:28 -0700 (PDT)") Message-ID: <873cj93p7z.fsf@cs.uga.edu> References: <20030520202728.42626.qmail@web12308.mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: owner-linux-mm@kvack.org Return-Path: To: Ravi Cc: linux-mm@kvack.org, kernelnewbies@nl.linux.org List-ID: Ravi writes: > Hi, > > I am looking at the latest mm/memory.c on Bitkeeper. > The comment for remap_pte_range() says "maps a range of > physical memory into the requested pages. the old mappings > are removed". But the code has this check: > > BUG_ON(!pte_none(*pte)); > > Why is it a bug to have a valid PTE when remap_pte_range() > is called? The 2.4 version of this fucntion cleared the > old PTE using ptep_get_and_clear() and then installed > a new one. Why was this changed? It used to be a call to forget_pte, and, as Flavio Bruno Leitner pointed out, wli changed it last year: http://www.ussg.iu.edu/hypermail/linux/kernel/0206.0/0053.html ... making forget_pte into a macro, which has since been completely inlined. The comment that used to be above the macro was this: bug check to be sure pte's are unmapped when no longer used -- --Ed L Cashin PGP public key: http://noserose.net/e/pgp/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org