From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757027Ab2LNSYH (ORCPT ); Fri, 14 Dec 2012 13:24:07 -0500 Received: from mailout39.mail01.mtsvc.net ([216.70.64.83]:38237 "EHLO n12.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756944Ab2LNSXd (ORCPT ); Fri, 14 Dec 2012 13:23:33 -0500 From: Peter Hurley To: Alan Cox , Jiri Slaby Cc: linux-serial@vger.kernel.org, Greg Kroah-Hartman , Ilya Zykov , Sasha Levin , linux-kernel@vger.kernel.org, Peter Hurley Subject: [PATCH v2 08/11] tty: Fix ldisc halt sequence on hangup Date: Fri, 14 Dec 2012 13:22:47 -0500 Message-Id: <1355509370-5883-9-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 1.8.0.1 In-Reply-To: <1355509370-5883-1-git-send-email-peter@hurleysoftware.com> References: <1355509370-5883-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 125194 peter@hurleysoftware.com X-MT-ID: 8fa290c2a27252aacf65dbc4a42f3ce3735fb2a4 X-MT-INTERNAL-ID: 8fa290c2a27252aacf65dbc4a42f3ce3735fb2a4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Flip buffer work cannot be cancelled until all outstanding ldisc references have been released. Convert the ldisc ref wait into a full ldisc halt with buffer work cancellation. Note that the legacy mutex is not held while cancelling. Signed-off-by: Peter Hurley --- drivers/tty/tty_ldisc.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 0d18d1e..c3dec37 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -549,22 +549,31 @@ static int tty_ldisc_halt(struct tty_struct *tty) } /** - * tty_ldisc_hangup_wait_idle - wait for the ldisc to become idle - * @tty: tty to wait for - * - * Wait for the line discipline to become idle. The discipline must - * have been halted for this to guarantee it remains idle. + * tty_ldisc_hangup_halt - halt the line discipline for hangup + * @tty: tty being hung up * + * Shut down the line discipline and work queue for the tty device + * being hungup. Clear the TTY_LDISC flag to ensure no further + * references can be obtained, wait for remaining references to be + * released, and cancel pending buffer work to ensure no more + * data is fed to the ldisc. * Caller must hold legacy and ->ldisc_mutex. * * NB: tty_set_ldisc() is prevented from changing the ldisc concurrently * with this function when it checks the TTY_HUPPING state. + * + * NB: if tty->ldisc is NULL then buffer work does not need to be + * cancelled because it must already have done as a precondition + * of setting tty->ldisc to NULL + * */ -static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty) +static bool tty_ldisc_hangup_halt(struct tty_struct *tty) { char cur_n[TASK_COMM_LEN], tty_n[64]; long timeout = 3 * HZ; + clear_bit(TTY_LDISC, &tty->flags); + if (tty->ldisc) { /* Not yet closed */ tty_unlock(tty); @@ -575,6 +584,10 @@ static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty) __func__, get_task_comm(cur_n, current), tty_name(tty, tty_n)); } + + cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); + /* must reacquire both locks and preserve lock order */ mutex_unlock(&tty->ldisc_mutex); tty_lock(tty); @@ -849,24 +862,11 @@ void tty_ldisc_hangup(struct tty_struct *tty) */ mutex_lock(&tty->ldisc_mutex); - /* - * this is like tty_ldisc_halt, but we need to give up - * the BTM before calling cancel_work_sync, which may - * need to wait for another function taking the BTM - */ - 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); - tty_lock(tty); - mutex_lock(&tty->ldisc_mutex); - /* At this point we have a closed ldisc and we want to reopen it. We could defer this to the next open but it means auditing a lot of other paths so this is a FIXME */ - if (tty_ldisc_hangup_wait_idle(tty)) { + if (tty_ldisc_hangup_halt(tty)) { if (reset == 0) { if (!tty_ldisc_reinit(tty, tty->termios.c_line)) -- 1.8.0.1