linux-kernel - Re: 'scheduling while atomic' during ppp connection on 2.6.37.1 and 2.6.38

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Date:	Mon, 21 Mar 2011 17:40:32 +0000
From:	Jack Stone <jwjstone@...tmail.fm>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Mac <kmac@...zta.fm>, linux-kernel@...r.kernel.org,
	linux-ppp@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: 'scheduling while atomic' during ppp connection on 2.6.37.1 and
 2.6.38

On 21/03/2011 11:27, Alan Cox wrote:
> It's quite likely that was as broken before your change as after. The
> locking in the code makes no sense so I flagged it up. The
> nozomi ntty_write also has lots of oddness in it that really needs
> sorting out.
> 
> I suspect that the chunk
> 
>         if (!dc || !port)
>                 return -ENODEV;
> 
>         mutex_lock(&port->tty_sem);
> 
>         if (unlikely(!port->port.count)) {
>                 DBG1(" ");
>                 goto exit;
>         }
> 
> and
> 
>       /* notify card */
>         if (unlikely(dc == NULL)) {
>                 DBG1("No device context?");
>                 goto exit;
>         }
> 
> and the mutex unlock are actually not doing anything
> 
> On the write_room case I think that as the code already uses tty_port
> helpers it needs to simply just return the correct value and not do all
> the other checks. chars_in_buffer() likewise
> 
> So in fact I don't think at this point the tty_sem needs replacing with
> anything, but the various bogus port.count checks want ripping out.
> 
> 

Thank you very much for the explanation. I will do my best to respin the
patch with appropriate changes.

Jack
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