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Date: Wed, 8 May 2013 16:47:43 +0800
From: wyang1 <Wei.Yang@windriver.com>
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To: Johannes Berg <johannes@sipsolutions.net>
CC: <linux-wireless@vger.kernel.org>, <wei.wyang@windriver.com>
Subject: Re: [PATCH] mac80211: refine ieee80211_rx() context requirement
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On 05/08/2013 04:37 PM, Johannes Berg wrote:
> On Wed, 2013-05-08 at 10:36 +0200, Johannes Berg wrote:
>> On Wed, 2013-05-08 at 16:31 +0800, Wei.Yang@windriver.com wrote:
>>> From: Wei Yang <Wei.Yang@windriver.com>
>>>
>>> In case of RT kernel, the return value of softirq_count() always
>>> equal to 0, we need to use in_serving_softirq to decide whether
>>> the current context is in softirq context.
>>> -	WARN_ON_ONCE(softirq_count() == 0);
>>> +	WARN_ON_ONCE(!in_serving_softirq());
>> As I understand the code, I don't believe this change to be correct. The
>> function can happily run with softirqs disabled (e.g.
>> local_bh_disable()), for example by being called via ieee80211_rx_ni().
>> As I understand in_serving_softirq(), it checks that it's actually
>> inside handling a softirq, no?
> Arguably, it should be
> 	WARN_ON_ONCE(!in_softirq());
>
> but that's equivalent:

Yeah, but the softirq is threaded in rt kernel, the softirq_count always 
return 0. The warning should always happen with rt kernel.

Wei
>
> include/linux/hardirq.h
>
>   * in_softirq - Are we currently processing softirq or have bh disabled?
>
>   #define in_softirq()           (softirq_count())
>
> johannes
>
>
>