linux-kernel - Re: [PATCH] x86, olpc: Eliminate BUG_ON and memset after alloc

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Message-ID: <alpine.DEB.2.02.1407211553190.29389@chino.kir.corp.google.com>
Date:	Mon, 21 Jul 2014 15:56:48 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Himangi Saraogi <himangi774@...il.com>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] x86, olpc: Eliminate BUG_ON and memset after
 alloc_bootmem

On Sat, 19 Jul 2014, Himangi Saraogi wrote:

> alloc_bootmem and related functions never return NULL and always return
> a zeroed region of memory.  Thus a BUG_ON the NULL test or memset after
> calls to these functions is unnecessary.
> 
> The following Coccinelle semantic patch was used for making the change:
> 
> @@
> expression E;
> statement S;
> @@
> 
> E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
> ... when != E
> - BUG_ON (E == NULL);
> 
> @@
> expression E,E1;
> @@
> 
> E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
> ... when != E
> - memset(E,0,E1);
> 
> Signed-off-by: Himangi Saraogi <himangi774@...il.com>
> Acked-by: Julia Lawall <julia.lawall@...6.fr>

Acked-by: David Rientjes <rientjes@...gle.com>

Many callers of alloc_bootmem() do not check for the return value because 
of this, there's no fallback available at this part in bootstrap so 
there's nothing else that can be done.
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