linux-kernel - Re: [PATCH 03/18] tty: Simplify tty buffer/ldisc interface with helper function

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Message-ID: <5148E9D2.4030305@izyk.ru>
Date:	Wed, 20 Mar 2013 02:42:26 +0400
From:	Ilya Zykov <linux@...k.ru>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, Min Zhang <mzhang@...sta.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/18] tty: Simplify tty buffer/ldisc interface with helper
 function

On 20.03.2013 0:21, Peter Hurley wrote:
> Ldisc interface functions must be called with interrupts enabled.
> Separating the ldisc calls into a helper function simplies the
> spin lock management.
> 
> Update the buffer's read index _after_ the data has been received
> by the ldisc.
> 

Hello Peter!
It looks good for me.
I think also we can remove two variables without waste:
(char_buf), (flag_buf) and use without (&buf->lock)
(head->char_buf_ptr + head->read), (head->char_buf_ptr + head->read),
because (head->read) guarded by (TTYP_FLUSHING).

I have little question about flush_to_ldisc().
Does can it be multithreaded?
I think yes, because on SMP schedule_work() can work on different CPU paralleled.

What do you think about this race condition?
https://lkml.org/lkml/2011/11/7/98

Thank you.
Ilya Zykov <linux@...k.ru>

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