linux-kernel - Re: [PATCH] staging: ks7010: fix wait_for_completion_interruptible

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Date:	Tue, 26 Jul 2016 06:43:34 +0000
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: ks7010: fix
 wait_for_completion_interruptible_timeout return handling

On Mon, Jul 25, 2016 at 10:54:03PM +0200, Wolfram Sang wrote:
> On Mon, Jul 25, 2016 at 09:21:50PM +0200, Nicholas Mc Guire wrote:
> > wait_for_completion_interruptible_timeout return 0 on timeout and 
> > -ERESTARTSYS if interrupted. The check for 
> > !wait_for_completion_interruptible_timeout() would report an interrupt
> > as timeout. Further, while HZ/50 will work most of the time it could 
> 
> Wouldn't it interpret -ERESTARTSYS as *no timeout*?
>

yup - actually the current code just treats the -ERESTARTSYS 
case as success.
 
> Anyway, the plain !0 comparison for me clearly shows that
> 'interruptible' was more copy&pasted then really planned or supported.
> If it was, it would need to cancel something. Also, 20ms is pretty hard
> to cancel for a user ;) Given all that and the troubles we had with
> 'interruptible' in the I2C subsystem, I'd much vote for dropping
> interruptible here.
> 
> > fail for HZ < 50, so this is switched to msecs_to_jiffies(20).
> 
> Rest looks good, thanks!
> 

thx!
hofrat