linux-kernel - Re: [PATCH] wan: dscc4: use msecs_to

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Message-ID: <20150607083137.GB9670@opentech.at>
Date:	Sun, 7 Jun 2015 10:31:37 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	David Miller <davem@...emloft.net>
Cc:	hofrat@...dl.org, romieu@...zoreil.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wan: dscc4: use msecs_to_jiffies for conversions

On Sun, 07 Jun 2015, David Miller wrote:

> From: Nicholas Mc Guire <hofrat@...dl.org>
> Date: Sat,  6 Jun 2015 10:41:06 +0200
> 
> > API compliance scanning with coccinelle flagged:
> > ./drivers/net/wan/dscc4.c:1036:1-33:
> >         WARNING: timeout (10) seems HZ dependent
> > ./drivers/net/wan/dscc4.c:554:2-34:
> >         WARNING: timeout (10) seems HZ dependent
> > ./drivers/net/wan/dscc4.c:599:2-34:
> >         WARNING: timeout (10) seems HZ dependent
> > 
> > Numeric constants passed to schedule_timeout_*() make the effective
> > timeout HZ dependent which does not seem to be the intent here.
> > Fixed up by converting the constant to jiffies with msecs_to_jiffies()
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> 
> Whoever wrote these things probably wanted whatever this amounts
> to when HZ=100, so that is the only valid transformation you can
> make to fix this up here.
> 
> Otherwise you seriously risk breaking the driver.

I did not find dscc4 in the 2.2 series of kernels so it does not predate
configurable HZ - or do you mean simply that increasing the timeout
here should be side-effect free and thus the larger of the values
should be taken ? - though that would imply that it is possibly now 
broken for HZ=1000. 

Will fix it up to 10 == 100ms and fix the patch documentation.

thx!
hofrat
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