From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261291AbVAUJRG (ORCPT ); Fri, 21 Jan 2005 04:17:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262196AbVAUJRG (ORCPT ); Fri, 21 Jan 2005 04:17:06 -0500 Received: from rproxy.gmail.com ([64.233.170.192]:33385 "EHLO rproxy.gmail.com") by vger.kernel.org with ESMTP id S261291AbVAUJQt (ORCPT ); Fri, 21 Jan 2005 04:16:49 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:mime-version:content-type:content-transfer-encoding; b=oadv3ntu9a0ns17WCPCn2A8NRvcf19jncnhFQpPcwbCyclrvcROSvCBAR0NnfUkQwD9Sxh6OOmOrHJtvvRbpnUSBVhSE6VA1ceeW9gSf0VqcckaByzPH1YpY3+EHVrBw8K8fJ5oADtV4So8VCePpDBZRCfvU3dU9yD4EEBuMxJk= Message-ID: <73e6204505012101165b8164c4@mail.gmail.com> Date: Fri, 21 Jan 2005 17:16:48 +0800 From: zhan rongkai Reply-To: zhan rongkai To: uclinux-dev@uclinux.org Subject: [PATCH] the page count of buddy seems to be buggy under no MMU Cc: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This set_page_refs() function is copied from linux-2.6.10 mm/page_alloc.c static inline void set_page_refs(struct page *page, int order) { #ifdef CONFIG_MMU set_page_count(page, 1); #else int i; /* * We need to reference all the pages for this order, otherwise if * anyone accesses one of the pages with (get/put) it will be freed. */ for (i = 0; i < (1 << order); i++) set_page_count(page+i, 1); #endif /* CONFIG_MMU */ } So when we are under no MMU, the __free_pages() function also should de-reference all the pages for this order (order > 0), too. However, the current __free_pages() only decrements the first page's refcount, which will cause __free_pages_ok() to dump stack! --------------------------------------------------------- --- linux-2.6.10.orig/mm/page_alloc.c 2004-12-25 05:33:51.000000000 +0800 +++ linux-2.6.10/mm/page_alloc.c 2005-01-21 17:14:08.000000000 +0800 @@ -786,6 +786,8 @@ free_hot_cold_page(pvec->pages[i], pvec->cold); } +#ifdef CONFIG_MMU + fastcall void __free_pages(struct page *page, unsigned int order) { if (!PageReserved(page) && put_page_testzero(page)) { @@ -796,6 +798,35 @@ } } +#else + +fastcall void __free_pages(struct page *page, unsigned int order) +{ + if (PageReserved(page)) + return; + + if (order == 0) { + if (put_page_testzero(page)) + free_hot_page(page); + } else { + int i, result = 0; + + /* + * We need to de-reference all the pages for this order -- see set_page_refs() + */ + for (i = 0; i < (1 << order); i++) + result += put_page_testzero(page + i); + + if (result) { + if (result != (1 << order)) + BUG(); + __free_pages_ok(page, order); + } + } +} + +#endif /* CONFIG_MMU */ + EXPORT_SYMBOL(__free_pages); fastcall void free_pages(unsigned long addr, unsigned int order) -- Rongkai Zhan