Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760765AbaLLGeg (ORCPT ); Fri, 12 Dec 2014 01:34:36 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51946 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759329AbaLLGQ5 (ORCPT ); Fri, 12 Dec 2014 01:16:57 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Peter Hurley" , "Greg Kroah-Hartman" Date: Fri, 12 Dec 2014 06:14:25 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 117/164] tty: Fix high cpu load if tty is unreleaseable In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:c97:8151:cc89:c28d X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley commit 37b164578826406a173ca7c20d9ba7430134d23e upstream. Kernel oops can cause the tty to be unreleaseable (for example, if n_tty_read() crashes while on the read_wait queue). This will cause tty_release() to endlessly loop without sleeping. Use a killable sleep timeout which grows by 2n+1 jiffies over the interval [0, 120 secs.) and then jumps to forever (but still killable). NB: killable just allows for the task to be rewoken manually, not to be terminated. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/tty/tty_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1594,6 +1594,7 @@ int tty_release(struct inode *inode, str int devpts; int idx; char buf[64]; + long timeout = 0; if (tty_paranoia_check(tty, inode, "tty_release_dev")) return 0; @@ -1721,7 +1722,11 @@ int tty_release(struct inode *inode, str "active!\n", tty_name(tty, buf)); tty_unlock(); mutex_unlock(&tty_mutex); - schedule(); + schedule_timeout_killable(timeout); + if (timeout < 120 * HZ) + timeout = 2 * timeout + 1; + else + timeout = MAX_SCHEDULE_TIMEOUT; } /* -- 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/