linux-kernel - Re: [PATCH 1/5] TTY: serial, use ASYNCB_CLOSING in uart

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Message-Id: <201108251715.01443.arnd@arndb.de>
Date:	Thu, 25 Aug 2011 17:15:01 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	gregkh@...e.de, alan@...ux.intel.com, linux-serial@...r.kernel.org,
	jirislaby@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] TTY: serial, use ASYNCB_CLOSING in uart_close

On Thursday 25 August 2011, Jiri Slaby wrote:
> 
> We need to move port->mutex locking after wait_until_sent in
> uart_close (for rationale see next patches). But if we did it now, we
> would introduce a race between close and open. This is exactly why
> port->mutex is locked at the top of uart_close.
> 
> To avoid the race, we add ASYNCB_CLOSING to uart_close. Like every
> other sane TTY driver. Thanks to tty_port_block_til_ready used in
> uart_open we will have this for free. Then we can move the port->mutex
> lock.
> 
> Also note that this will make the conversion to tty_port helpers
> easier. They are currently handling ASYNC_CLOSING flag correctly.
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>

The series looks good to me,

Acked-by: Arnd Bergmann <arnd@...db.de>

The only thing left to note is probably that there are a bunch
of drivers that implement their own *_wait_until_sent function
and call that from their *_close function instead of calling
tty_wait_until_sent. These drivers continue to suffer from the
same stalls that you are fixing the other ones.

	Arnd
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