From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch 4/5] net: hip04: Make tx coalesce timer actually work
Date: Tue, 14 Apr 2015 00:08:23 +0200 (CEST)
Message-ID: <alpine.DEB.2.11.1504140007570.3845@nanos>
References: <20150413210009.682000343@linutronix.de> <9614284.QjZ4xls6zV@wuerfel> <alpine.DEB.2.11.1504132338080.3845@nanos> <3040901.Bp3bfgc1te@wuerfel>
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Cc: LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	dingtianhong <dingtianhong@huawei.com>,
	Zhangfei Gao <zhangfei.gao@linaro.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	netdev@vger.kernel.org
To: Arnd Bergmann <arnd@arndb.de>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <3040901.Bp3bfgc1te@wuerfel>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

On Tue, 14 Apr 2015, Arnd Bergmann wrote:
> On Monday 13 April 2015 23:42:03 Thomas Gleixner wrote:
> > > 
> > > Question: this looks to me like it sets both the minimum and maximum
> > > time to priv->tx_coalesce_usecs/2, when the intention was to set
> > > the minimum to priv->tx_coalesce_usecs/2 and the maximum to
> > > priv->tx_coalesce_usecs. Am I missing something subtle here, or did
> > > you just misread my original intention from the botched code?
> > 
> > Yes, I missed that. Simple fix for this is:
> > 
> >   unsigned long t_ns = priv->tx_coalesce_usecs * NSEC_PER_USEC / 2;
> >   
> >   hrtimer_start_range_ns(&priv->tx_coalesce_timer, ns_to_ktime(t_ns),
> >                          t_ns, HRTIMER_MODE_REL);
> 
> Ah, good. I have to admit that I'd probably make the same mistake
> again if I was to do this for another driver and you hadn't sent
> the fix. The hrtimer_set_expires_range() function just looked like
> it had been designed for the use case I was interested in ;-).
> 
> Any idea how to prevent the next person from making the same mistake?

Yes. Documentation :)

Thanks,

	tglx