On Wed, 9 Dec 2015, 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.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Nicolas Pitre <nico@xxxxxxxxxx>
>
> diff --git a/drivers/net/wireless/intel/iwlegacy/common.c b/drivers/net/wireless/intel/iwlegacy/common.c
> index 887114582583..6308bb217454 100644
> --- a/drivers/net/wireless/intel/iwlegacy/common.c
> +++ b/drivers/net/wireless/intel/iwlegacy/common.c
> @@ -3602,7 +3602,7 @@ il_is_ht40_tx_allowed(struct il_priv *il, struct ieee80211_sta_ht_cap *ht_cap)
> }
> EXPORT_SYMBOL(il_is_ht40_tx_allowed);
>
> -static u16
> +static u16 noinline
> il_adjust_beacon_interval(u16 beacon_val, u16 max_beacon_val)
> {
> u16 new_val;
>
>
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