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

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Message-ID: <CAPybu_3b6epYcQ1c0L0E1so7BNJ7DndA4E2nHDfj8OYjR3u0Zw@mail.gmail.com>
Date:	Thu, 9 Oct 2014 10:07:38 +0200
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Alan Cox <alan@...ux.intel.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.

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?

Thanks!

-- 
Ricardo Ribalda
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