From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935235Ab3BTUEr (ORCPT ); Wed, 20 Feb 2013 15:04:47 -0500 Received: from mailout02.c08.mtsvc.net ([205.186.168.190]:53920 "EHLO mailout02.c08.mtsvc.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935190Ab3BTUEn (ORCPT ); Wed, 20 Feb 2013 15:04:43 -0500 From: Peter Hurley To: Greg Kroah-Hartman , Jiri Slaby Cc: Sasha Levin , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Ilya Zykov , Dave Jones , Michael Ellerman , Shawn Guo , Peter Hurley Subject: [PATCH v4 01/32] tty: Add diagnostic for halted line discipline Date: Wed, 20 Feb 2013 15:02:48 -0500 Message-Id: <1361390599-15195-2-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1361390599-15195-1-git-send-email-peter@hurleysoftware.com> References: <1361390599-15195-1-git-send-email-peter@hurleysoftware.com> In-Reply-To: <1360095638-6624-1-git-send-email-peter@hurleysoftware.com> References: <1360095638-6624-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 125194 peter@hurleysoftware.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Flip buffer work must not be scheduled by the line discipline after the line discipline has been halted; issue warning. Note: drivers can still schedule flip buffer work. Signed-off-by: Peter Hurley --- drivers/tty/n_tty.c | 8 ++++++++ drivers/tty/tty_ldisc.c | 7 ++++++- include/linux/tty.h | 1 + 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 05e72be..9c18e37 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -153,6 +153,12 @@ static void n_tty_set_room(struct tty_struct *tty) if (left && !old_left) { WARN_RATELIMIT(tty->port->itty == NULL, "scheduling with invalid itty\n"); + /* see if ldisc has been killed - if so, this means that + * even though the ldisc has been halted and ->buf.work + * cancelled, ->buf.work is about to be rescheduled + */ + WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags), + "scheduling buffer work for halted ldisc\n"); schedule_work(&tty->port->buf.work); } } @@ -1645,6 +1651,8 @@ static int n_tty_open(struct tty_struct *tty) goto err_free_bufs; tty->disc_data = ldata; + /* indicate buffer work may resume */ + clear_bit(TTY_LDISC_HALTED, &tty->flags); reset_buffer_flags(tty); tty_unthrottle(tty); ldata->column = 0; diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index d794087..c641321 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -375,6 +375,7 @@ static inline void tty_ldisc_put(struct tty_ldisc *ld) void tty_ldisc_enable(struct tty_struct *tty) { + clear_bit(TTY_LDISC_HALTED, &tty->flags); set_bit(TTY_LDISC, &tty->flags); clear_bit(TTY_LDISC_CHANGING, &tty->flags); wake_up(&tty_ldisc_wait); @@ -513,8 +514,11 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) static int tty_ldisc_halt(struct tty_struct *tty) { + int scheduled; clear_bit(TTY_LDISC, &tty->flags); - return cancel_work_sync(&tty->port->buf.work); + scheduled = cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); + return scheduled; } /** @@ -820,6 +824,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) clear_bit(TTY_LDISC, &tty->flags); tty_unlock(tty); cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); mutex_unlock(&tty->ldisc_mutex); retry: tty_lock(tty); diff --git a/include/linux/tty.h b/include/linux/tty.h index c75d886..7aa4be6 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -315,6 +315,7 @@ struct tty_file_private { #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ #define TTY_HUPPED 18 /* Post driver->hangup() */ #define TTY_HUPPING 21 /* ->hangup() in progress */ +#define TTY_LDISC_HALTED 22 /* Line discipline is halted */ #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty)) -- 1.8.1.2