linux-kernel - Re: [PATCH v3] mtd: cfi: reduce stack size

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Date:	Tue, 10 Mar 2015 22:00:14 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Jingoo Han <jg1.han@...sung.com>,
	linux-mtd@...ts.infradead.org,
	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mtd: cfi: reduce stack size

On Tuesday 10 March 2015, Brian Norris wrote:
> On Tue, Mar 10, 2015 at 05:48:37PM +0100, Arnd Bergmann wrote:
> > The cfi_staa_write_buffers function uses a large amount of kernel stack
> > whenever CONFIG_MTD_MAP_BANK_WIDTH_32 is set, and that results in a
> > warning on ARM allmodconfig builds:
> > 
> > drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_write_buffers':
> > drivers/mtd/chips/cfi_cmdset_0020.c:651:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> > 
> > It turns out that this is largely a result of a suboptimal implementation
> > of map_word_andequal(). Replacing this function with a straightforward
> > one reduces the stack size in this function by exactly 200 bytes,
> > shrinks the .text segment for this file from 27648 bytes to 26608 bytes,
> > and makes the warning go away.
> 
> Patch looks OK to me, and those results are nice.
> 
> Did you (or anyone else) do any testing?

No runtime tests, I only built them, sorry.

	Arnd
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