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Date: Tue, 24 May 2011 14:34:32 +0200
From: Richard Cochran <richardcochran@gmail.com>
To: Nicolas Kaiser <nikai@nikai.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Richard Cochran <richard.cochran@omicron.at>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] posix clocks: correct error value in posix_clock_poll()
Message-ID: <20110524123432.GB2929@riccoc20.at.omicron.at>
References: <20110524125147.0eb112b5@absol.kitzblitz>
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On Tue, May 24, 2011 at 12:51:47PM +0200, Nicolas Kaiser wrote:
> Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
> ---
> It looks to me like -ENODEV might not be a good return value
> in poll(). Would POLLERR be the correct one in this case?
> 
>  kernel/time/posix-clock.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
> index c340ca6..2424d3f 100644
> --- a/kernel/time/posix-clock.c
> +++ b/kernel/time/posix-clock.c
> @@ -71,7 +71,7 @@ static unsigned int posix_clock_poll(struct file *fp, poll_table *wait)
>  	int result = 0;
>  
>  	if (!clk)
> -		return -ENODEV;
> +		return POLLERR;

The condition (!clk) is only satisfied when 'zombie' is set,
indicating that the dynamic clock has disappeared. That is why the
file operations uniformly return ENODEV. So, I think it makes sense
the way that it is.

In addition, man 2 poll says,

   POLLERR
          Error condition (output only).

so using that error code would be misleading, IMHO.

Thanks,
Richard
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