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

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Message-ID: <20161205101516.GA24936@amd>
Date:   Mon, 5 Dec 2016 11:15:16 +0100
From:   Pavel Machek <pavel@....cz>
To:     Giuseppe CAVALLARO <peppe.cavallaro@...com>
Cc:     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.

Hi!

> >>In the ring, some descriptors can raise the irq (according to a
> >>threshold) and set the IC bit. In this path, the NAPI  poll will be
> >>scheduled.
> >
> >Not NAPI poll but stmmac_tx_timer(), right?
> 
> in the xmit according the the threshold the timer is started or the
> interrupt is set inside the descriptor.
> Then stmmac_tx_clean will be always called and, if you see the flow,
> no irqlock protection is needed!

Actually, I was wrong. irqlock protection is needed, since
stmmac_tx_clean() is called from timer, and that's interrupt context,
as you can confirm using BUG_ON(in_interrupt());

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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