linux-kernel - Re: [PATCH V2] n_gsm: race between ld close and gsmtty open

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Date:	Tue, 26 Nov 2013 11:35:14 +0800
From:	channing <chao.bi@...el.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, fengguang.wu@...el.com
Subject: Re: [PATCH V2] n_gsm: race between ld close and gsmtty open

On Mon, 2013-11-25 at 18:54 -0800, Greg KH wrote:
> On Tue, Nov 26, 2013 at 11:14:05AM +0800, channing wrote:

> > This patch is try to avoid it by:
> > 
> > 1) in n_gsm driver, use a global gsm mutex lock to avoid gsm_dlci_release() run in
> > parallel with gsmtty_install();
The commit is updated here than formal patch set: we use mutex lock in
patch V2, while use spin lock in patch V1.

> > 
> > 2) Increase dlci's ref count in gsmtty_install() instead of in gsmtty_open(), the
> > purpose is to prevent gsm_dlci_release() releasing dlci after gsmtty_install()
> > allocats dlci but before gsmtty_open increases dlci's ref count;
> > 
> > 3) Decrease dlci's ref count in gsmtty_remove(), a tty framework API, this is the
> > opposite process of step 2).
> > 
> > Signed-off-by: Chao Bi <chao.bi@...el.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> I have not signed off on this additional patch.
> 
> What is different from the previous version?  That information needs to
> be somewhere, otherwise I'm just going to guess and say this is the same
> as your last one, which was incorrect.
The difference with previous one is to use a mutex instead of spin lock
to avoid race, purpose is to avoid sleep in atomic context. I've also
updated commit a little as above.

> 
> Also, please fix your "From:" line in your email client to match your
> Signed-off-by: line, or else add the proper "From:" line to your patch,
> as the Documentation/SubmittingPatches file says.
> 
> Care to try again?
Yes, I'll correct it. thanks.
> 
> greg k-h


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