linux-kernel - Re: [PATCH] tty/n_gsm.c: do not clear gsm

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Date:	Thu, 9 Oct 2014 12:13:51 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	"xinhui.pan" <xinhuix.pan@...el.com>, Jiri Slaby <jslaby@...e.cz>,
	linux-kernel@...r.kernel.org,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	mnipxh <mnipxh@...il.com>, gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH] tty/n_gsm.c: do not clear gsm_mux entry when the gsm is
 not closed

On Thu, Oct 09, 2014 at 03:01:46PM -0400, Peter Hurley wrote:
> On 07/28/2014 11:13 AM, Greg Kroah-Hartman wrote:
> > On Mon, Jul 28, 2014 at 03:16:25PM +0800, xinhui.pan wrote:
> >>> Why can't you do dynamic reference counting of your structure, that
> >>> would allow you to get rid of your global array, right?
> >>>
> >>
> >> Thanks for your nice comments.
> >> Struct gsm has a ref-count already. :)
> > 
> > Then you should be fine, no need to keep it in an array.
> > 
> >> And also adding a ref-count is a little hard to me. :(
> >> This global array is used to keep tracking the gsms that stands for the gsmttyXX.
> > 
> > You shouldn't need that at all, just use a list, you don't care what the
> > XX number is within the driver, just allocate a new one with the next
> > available number and you should be fine.
> > 
> >> and it can tell us if we can create a new gsm. :)
> > 
> > You should always be able to create a new gsm if you need to :)
> > 
> >> In gsm_init we set *gsm_tty_driver = alloc_tty_driver(256);*
> > 
> > Why limit to 256?  Just use a list, and a idr structure to allocate the
> > minor number, and all should be good.
> 
> Hi Greg,
> 
> This is still broken in the gsm driver.
> 
> As much as I'd like to see someone take ownership of the gsm driver and
> do this 'the right way', I think until that happens we should consider
> fixing the reuse-while-in-use error.

What happened to the gsm driver maintainers?

> Would you be willing to take a patch from me that just does the bare
> minimum to keep this from panicking in the cdev code?

Depends on what the patch looks like :)

Send it on, and I'll be glad to review it.

thanks,

greg k-h
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