netdev - Re: [net-next.git 3/8 (V2)] stmmac: add the initial tx coalesce schema

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Message-ID: <1347570650.13258.40.camel@deadeye.wl.decadent.org.uk>
Date:	Thu, 13 Sep 2012 22:10:50 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...emloft.net>
CC:	<peppe.cavallaro@...com>, <netdev@...r.kernel.org>
Subject: Re: [net-next.git 3/8 (V2)] stmmac: add the initial tx coalesce
 schema

On Thu, 2012-09-13 at 16:46 -0400, David Miller wrote:
> From: Ben Hutchings <bhutchings@...arflare.com>
> Date: Thu, 13 Sep 2012 21:42:51 +0100
> 
> > On Thu, 2012-09-13 at 16:23 -0400, David Miller wrote:
> >> From: Giuseppe CAVALLARO <peppe.cavallaro@...com>
> >> Date: Tue, 11 Sep 2012 08:55:09 +0200
> >> 
> >> > +	unsigned long flags;
> >> > +
> >> > +	spin_lock_irqsave(&priv->tx_lock, flags);
> >> >  
> >> > -	spin_lock(&priv->tx_lock);
> >> > +	priv->xstats.tx_clean++;
> >> 
> >> You are changing the locking here for the sake of the new timer.
> >> 
> >> But timers run in software interrupt context, so this change is
> >> completely unnecessary since NAPI runs in software interrupt context
> >> as well, and neither timers nor NAPI run in hardware interrupts
> >> context.
> > 
> > NAPI pollers can be called by netpoll in hardware interrupt context, and
> > this driver supports netpoll.
> 
> And the netpoll handler need to make amends to make sure that
> hardware the environment expected by the software interrupt
> code is preserved.
>
> Well written NAPI drivers never need to disable hardware interrupts
> in their ->poll() method and it's callers, neither should you.

Perhaps you should get round to reviewing netpoll, because it does
exactly this.

> I'm not considering your patches until you implement this properly.

These aren't my patches.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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