From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758232AbYKWKqj (ORCPT ); Sun, 23 Nov 2008 05:46:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756074AbYKWKq3 (ORCPT ); Sun, 23 Nov 2008 05:46:29 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:47336 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755883AbYKWKq2 (ORCPT ); Sun, 23 Nov 2008 05:46:28 -0500 Date: Sun, 23 Nov 2008 11:46:21 +0100 (CET) From: Julia Lawall To: rmk@arm.linux.org.uk, linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: [PATCH 1/5] arch/arm: Eliminate NULL test and memset after alloc_bootmem Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Julia Lawall As noted by Akinobu Mita in patch b1fceac2b9e04d278316b2faddf276015fc06e3b, alloc_bootmem and related functions never return NULL and always return a zeroed region of memory. Thus a NULL test or memset after calls to these functions is unnecessary. This was fixed using the following semantic patch. (http://www.emn.fr/x-info/coccinelle/) // @@ expression E; statement S; @@ E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...) ... when != E ( - BUG_ON (E == NULL); | - if (E == NULL) S ) @@ expression E,E1; @@ E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...) ... when != E - memset(E,0,E1); // Signed-off-by: Julia Lawall --- arch/arm/mm/mmu.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 9a17d51..6eb9f26 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -819,7 +819,6 @@ static void __init devicemaps_init(struct machine_desc *mdesc) * Allocate the vector page early. */ vectors = alloc_bootmem_low_pages(PAGE_SIZE); - BUG_ON(!vectors); for (addr = VMALLOC_END; addr; addr += PGDIR_SIZE) pmd_clear(pmd_off_k(addr)); @@ -904,10 +903,10 @@ void __init paging_init(struct machine_desc *mdesc) top_pmd = pmd_off_k(0xffff0000); /* - * allocate the zero page. Note that we count on this going ok. + * allocate the zero page. Note that this always succeeds and + * returns a zeroed result. */ zero_page = alloc_bootmem_low_pages(PAGE_SIZE); - memset(zero_page, 0, PAGE_SIZE); empty_zero_page = virt_to_page(zero_page); flush_dcache_page(empty_zero_page); }