linux-kernel - Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

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Message-ID: <98fb3577-5f31-bf17-3e02-96c150854108@gmx.de>
Date:   Mon, 5 Dec 2016 23:54:30 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Pavel Machek <pavel@....cz>
Cc:     Giuseppe CAVALLARO <peppe.cavallaro@...com>,
        alexandre.torgue@...com, David Miller <davem@...emloft.net>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

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