Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754718Ab2K2ON7 (ORCPT ); Thu, 29 Nov 2012 09:13:59 -0500 Received: from 95-31-19-74.broadband.corbina.ru ([95.31.19.74]:51357 "EHLO 95-31-19-74.broadband.corbina.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754397Ab2K2ON5 (ORCPT ); Thu, 29 Nov 2012 09:13:57 -0500 Message-ID: <50B76D96.20809@ilyx.ru> Date: Thu, 29 Nov 2012 18:13:42 +0400 From: Ilya Zykov 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 CC: Xiaobing Tu , Alan Cox , Jiri Slaby , Alek Du , Greg Kroah-Hartman , 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1895 Lines: 56 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 > Sorry, In you reply not all patch. Main idea here - we never flash last (struct tty_buffer) in the active buffer. Only data for ldisc. (tty->buf.head->read = tty->buf.head->commit). At that moment driver can collect(write) data in buffer without conflict. --- 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; } - tty->buf.tail = NULL; + WARN_ON(tty->buf.head != tty->buf.tail); + tty->buf.head->read = tty->buf.head->commit; } /** -- 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/