Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1945928Ab2K2ADq (ORCPT ); Wed, 28 Nov 2012 19:03:46 -0500 Received: from 95-31-19-74.broadband.corbina.ru ([95.31.19.74]:50764 "EHLO 95-31-19-74.broadband.corbina.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945896Ab2K2ADp (ORCPT ); Wed, 28 Nov 2012 19:03:45 -0500 Message-ID: <50B6A652.9000107@ilyx.ru> Date: Thu, 29 Nov 2012 04:03:30 +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: Xiaobing Tu CC: Alan Cox , Jiri Slaby , Alek Du , Greg Kroah-Hartman , ilya@ilyx.ru, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Fwd: [PATCH] tty: Correct tty buffer flushing. References: <50B55A93.4090900@ilyx.ru> In-Reply-To: <50B55A93.4090900@ilyx.ru> X-Forwarded-Message-Id: <50B55A93.4090900@ilyx.ru> 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: 1529 Lines: 42 This patch abolish: [PATCH] tty: hold lock across tty buffer finding and buffer filling. commit f8f72f047b96c6c8b13f6e3ba53fa6feb4266813 The commit f8f72f047 very dirty, has many degradation on SMP systems, because take spinlock at long time, and it doesn't resolve problem with tty_prepare_string*(). We lose all advantage from the use of flip buffer. Can't write/read to/from buffer without lock. The root of problem it use carelessly buffer flushing, then another thread can write to it. This patch resolves this problem and doesn't let lose advantage from flip buffer use. Signed-off-by: Ilya Zykov --- 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; } - 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/