Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753072AbaJPUZx (ORCPT ); Thu, 16 Oct 2014 16:25:53 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:50066 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751928AbaJPUZr (ORCPT ); Thu, 16 Oct 2014 16:25:47 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Jiri Slaby , linux-serial@vger.kernel.org, One Thousand Gnomes , Peter Hurley Subject: [PATCH -next 02/27] tty: Invert tty_lock/ldisc_sem lock order Date: Thu, 16 Oct 2014 16:25:00 -0400 Message-Id: <1413491125-20134-3-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.1.1 In-Reply-To: <1413491125-20134-1-git-send-email-peter@hurleysoftware.com> References: <1413491125-20134-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dropping the tty lock to acquire the tty->ldisc_sem allows several race conditions (such as hangup while changing the ldisc) which requires extra states and testing. The ldisc_sem->tty_lock lock order has not been required since tty buffer ownership was moved to tty_port. Signed-off-by: Peter Hurley --- drivers/tty/tty_ldisc.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 332a622..28858eb 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -523,9 +523,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); + tty_lock(tty); retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ); if (retval) { tty_ldisc_put(new_ldisc); + tty_unlock(tty); return retval; } @@ -536,11 +538,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (tty->ldisc->ops->num == ldisc) { tty_ldisc_enable_pair(tty, o_tty); tty_ldisc_put(new_ldisc); + tty_unlock(tty); return 0; } old_ldisc = tty->ldisc; - tty_lock(tty); if (test_bit(TTY_HUPPING, &tty->flags) || test_bit(TTY_HUPPED, &tty->flags)) { @@ -675,8 +677,6 @@ void tty_ldisc_hangup(struct tty_struct *tty) wake_up_interruptible_poll(&tty->write_wait, POLLOUT); wake_up_interruptible_poll(&tty->read_wait, POLLIN); - tty_unlock(tty); - /* * Shutdown the current line discipline, and reset it to * N_TTY if need be. @@ -684,7 +684,6 @@ void tty_ldisc_hangup(struct tty_struct *tty) * Avoid racing set_ldisc or tty_ldisc_release */ tty_ldisc_lock_pair(tty, tty->link); - tty_lock(tty); if (tty->ldisc) { -- 2.1.1 -- 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/