linux-kernel - Re: [GIT PULL] TTY/Serial driver fixes for 5.5-rc3

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Date:   Fri, 27 Dec 2019 18:30:11 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-serial@...r.kernel.org
Subject: Re: [GIT PULL] TTY/Serial driver fixes for 5.5-rc3

On Mon, Dec 23, 2019 at 07:06:51AM -0500, Greg KH wrote:
> On Fri, Dec 20, 2019 at 10:08:03AM -0800, Linus Torvalds wrote:
> > On Thu, Dec 19, 2019 at 11:07 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > The last tty core fix should resolve a long-standing bug with a race
> > > at port creation time that some people would see, and Sudip finally
> > > tracked down.
> > 
> > Hmm, looks good. But it makes me wonder if we should now try to remove
> > the second call to tty_port_link_device()?
> > 
> > Now we have a number of helpers that do that tty_port_link_device()
> > call for the driver (eg tty_port_register_device_attr_serdev(),
> > tty_port_register_device_attr(), and the just added
> > uart_add_one_port()).
> > 
> > But we also have drivers doing it by hand, and presumably we now have
> > drivers that do it through multiple paths? I guess it's harmless, but
> > it feels a bit odd. No?
> 
> It does.  I'll try to look at this after the holidays unless Sudip beats
> me to it.

The second call to tty_port_link_device() is in
tty_port_register_device_attr_serdev() and tty_port_register_device_attr()
is being called from many other places apart from uart_add_one_port().
The attached patch should be safe. I will test and send it properly unless
someone objects to it.

--
Regards
Sudip

View attachment "patch" of type "text/plain" (2337 bytes)