linux-kernel - [PATCH 6/14] arch/parisc: Eliminate NULL test and memset after alloc

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Message-ID: <Pine.LNX.4.64.0806241023080.26777@ask.diku.dk>
Date:	Tue, 24 Jun 2008 10:23:28 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	akinobu.mita@...il.com, kyle@...artin.ca, matthew@....cx,
	grundler@...isc-linux.org, linux-parisc@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 6/14] arch/parisc: Eliminate NULL test and memset after
 alloc_bootmem

From: Julia Lawall <julia@...u.dk>

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.

 arch/parisc/mm/init.c |    1 -
 1 file changed, 1 deletion(-)

This was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression E;
statement S;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
... when != E
(
- BUG_ON (E == NULL);
|
- if (E == NULL) S
)

@@
expression E,E1;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
... when != E
- memset(E,0,E1);
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>
---

diff -u -p a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -765,7 +765,6 @@ static void __init pagetable_init(void)
 #endif
 
 	empty_zero_page = alloc_bootmem_pages(PAGE_SIZE);
-	memset(empty_zero_page, 0, PAGE_SIZE);
 }
 
 static void __init gateway_init(void)
--
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