Subject: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.
To: Pavel Machek <pavel@ucw.cz>
References: <20161124085506.GA25007@amd>
 <20161124.110416.198867271899443489.davem@davemloft.net>
 <20161124212540.GA24796@amd> <b6ac7a3c-6774-9568-1cc0-97074eaa928f@st.com>
 <20161202084511.GA32294@amd> <3192a4b6-1e97-048f-a0dd-bfc0f3d96ed8@st.com>
 <20161205101516.GA24936@amd>
 <trinity-efd00e93-2b37-4543-a199-e2cbed9fe455-1480937999976@3capp-gmx-bs18>
 <20161205220221.GA19135@amd> <9a85da24-85cf-f94e-908f-a10eecac2369@gmx.de>
 <20161205224057.GB19135@amd>
Cc: Giuseppe CAVALLARO <peppe.cavallaro@st.com>, alexandre.torgue@st.com,
        David Miller <davem@davemloft.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
From: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Message-ID: <98fb3577-5f31-bf17-3e02-96c150854108@gmx.de>
Date: Mon, 5 Dec 2016 23:54:30 +0100
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On 05.12.2016 23:40, Pavel Machek wrote:
> On Mon 2016-12-05 23:37:09, Lino Sanfilippo wrote:
>> Hi Pavel,
>> 
>> On 05.12.2016 23:02, Pavel Machek wrote:
>> > 
>> > we need spin_lock_bh at minimum, as we are locking user context
>> > against timer.
>> > 
>> > Best regards,
>> > 									Pavel
>> > 
>> 
>> I was referring to stmmac_tx_clean() which AFAICS is only called from softirq context,
>> (one time in the timer handler and one time in napi poll handler) so a spin_lock() should
>> be sufficient. I cant see how this is called from userspace. If it were, a spin_lock_bh() had
>> to be used, of course.
> 
> stmmac_tx_clean() shares lock with stmmac_tx() -- and that's process
> context as far as I can tell. So... spin_lock_bh() at
> minimum... right?
> 
> 									Pavel
> 

You mean stmmac_xmit()? Thats also softirq AFAICT, its the TX softirq....

Regards,
Lino