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

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Message-ID: <20161205220221.GA19135@amd>
Date:   Mon, 5 Dec 2016 23:02:21 +0100
From:   Pavel Machek <pavel@....cz>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
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.

Hi!

> > 
> > 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());
> > 
> 
> in_interrupt() can mean both softirq and hardirq context. In this case it
> means softirq. So I guess you were right before, and no irq locking is needed.

Are you absolutely sure? Because my testing seems to indicate
otherwise (but I may have made a mistake).

According to

https://www.kernel.org/pub/linux/kernel/people/rusty/kernel-locking/c214.html

we need spin_lock_bh at minimum, as we are locking user context
against timer.

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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