linux-kernel - Re: [PATCH 03/12] serial_core: Handle TIOC[GS]RS485 ioctls.

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Message-ID: <1412864192.28467.72.camel@acox1-desk.ger.corp.intel.com>
Date:	Thu, 09 Oct 2014 15:16:32 +0100
From:	Alan Cox <alan@...ux.intel.com>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-serial@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/12] serial_core: Handle TIOC[GS]RS485 ioctls.

On Thu, 2014-10-09 at 10:07 +0200, Ricardo Ribalda Delgado wrote:
> Hello Alan
> 
> >
> > What is the locking between setting/getting/driver use of the config ?
> > This really needs a lock (termios sem I think is perhaps appropriate
> > given when the values are normally referenced).
> 
> I tried implementing it with the sermios sem
> ((&(uart_port)->state->port.tty->termios_rwsem)), but some drivers
> access the rs485 structure inside their irq handler. So I have see
> options here
> 
> 1) Protect the structure with uart_port->lock spinlock
> 2) Assume that an assignment is atomic on critical sections where I
> cannot hold the rwsem.
> 
> I think 1) is more correct. Any issues that I continue in this
> direction? Any better idea?

For uart #1 sounds right to me too.

Alan


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