linux-kernel - Re: [PATCH] iwlegacy: mark il_adjust_beacon

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Message-ID: <20151210110801.GA2010@redhat.com>
Date:	Thu, 10 Dec 2015 12:08:02 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Kalle Valo <kvalo@...eaurora.org>, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, nico@...aro.org
Subject: Re: [PATCH] iwlegacy: mark il_adjust_beacon_interval as noinline

On Wed, Dec 09, 2015 at 05:42:41PM +0100, Arnd Bergmann wrote:
> With the new optimized do_div() code, some versions of gcc
> produce obviously incorrect code that leads to a link error
> in iwlegacy/common.o:
> 
> drivers/built-in.o: In function `il_send_rxon_timing':
> :(.text+0xa6b4d4): undefined reference to `____ilog2_NaN'
> :(.text+0xa6b4f0): undefined reference to `__aeabi_uldivmod'
> 
> In a few thousand randconfig builds, I have seen this problem
> a couple of times in this file, but never anywhere else in the
> kernel, so we can try to work around this in the only file
> that shows the behavior, by marking the il_adjust_beacon_interval
> function as noinline, which convinces gcc to use the unoptimized
> do_div() all the time.

I don't think this is good way to "fix" the issue, but also have
nothing against to this particular change.

Acked-by: Stanislaw Gruszka <sgruszka@...hat.com>
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