Message-ID: <50B76B45.1080809@ilyx.ru>
Date: Thu, 29 Nov 2012 18:03:49 +0400
From: Ilya Zykov <ilya@ilyx.ru>
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:16.0) Gecko/20121026 Thunderbird/16.0.2
MIME-Version: 1.0
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Xiaobing Tu <xiaobing.tu@intel.com>, Alan Cox <alan@linux.intel.com>,
        Jiri Slaby <jslaby@suse.cz>, Alek Du <alek.du@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: [PATCH] tty: Correct tty buffer flushing.
References: <50B55A93.4090900@ilyx.ru> <50B6A652.9000107@ilyx.ru> <20121129135418.4237e7f8@pyramind.ukuu.org.uk>
In-Reply-To: <20121129135418.4237e7f8@pyramind.ukuu.org.uk>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1522
Lines: 46

On 29.11.2012 17:54, Alan Cox wrote:
>> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
>> index 6c9b7cd..4f02f9c 100644
>> --- a/drivers/tty/tty_buffer.c
>> +++ b/drivers/tty/tty_buffer.c
>> @@ -114,11 +114,14 @@ static void __tty_buffer_flush(struct tty_struct *tty)
>>  {
>>  	struct tty_buffer *thead;
>>  
>> -	while ((thead = tty->buf.head) != NULL) {
>> -		tty->buf.head = thead->next;
>> -		tty_buffer_free(tty, thead);
>> +	if (tty->buf.head == NULL)
>> +		return;
>> +	while ((thead = tty->buf.head->next) != NULL) {
>> +		tty_buffer_free(tty, tty->buf.head);
>> +		tty->buf.head = thead;
> 
> This part of the change seems to have no effect at all. There are no
> locks held so there is nothing guaranteeing how the other processors
> views of the order of operations will be affected.
> 
> Alan
> 
/**
 *	__tty_buffer_flush		-	flush full tty buffers
 *	@tty: tty to flush
 *
 *	flush all the buffers containing receive data. Caller must
 *	hold the buffer lock and must have ensured no parallel flush to
 *	ldisc is running.
 *
 *	Locking: Caller must hold tty->buf.lock
 */

Please, don't ignore my patch.
Please, Look at it one more time thoroughly.
Before REVERT [PATCH] tty: hold lock across tty buffer finding and buffer filling.
Thank you.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/