Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755888AbaKROVZ (ORCPT ); Tue, 18 Nov 2014 09:21:25 -0500 Received: from cantor2.suse.de ([195.135.220.15]:56994 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932206AbaKROKV (ORCPT ); Tue, 18 Nov 2014 09:10:21 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Hurley , Jiri Slaby Subject: [PATCH 3.12 184/206] tty: Fix high cpu load if tty is unreleaseable Date: Tue, 18 Nov 2014 15:08:59 +0100 Message-Id: <866f9fec24ee1dfa4a40e1d166b6ce3f4c3736de.1416319692.git.jslaby@suse.cz> X-Mailer: git-send-email 2.1.3 In-Reply-To: <28f04bcc068a44c5641c727883947960fb8dcbd5.1416319692.git.jslaby@suse.cz> References: <28f04bcc068a44c5641c727883947960fb8dcbd5.1416319692.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Hurley 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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: Jiri Slaby --- drivers/tty/tty_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index d3448a90f0f9..25d07412e08e 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1701,6 +1701,7 @@ int tty_release(struct inode *inode, struct file *filp) int pty_master, tty_closing, o_tty_closing, do_sleep; int idx; char buf[64]; + long timeout = 0; if (tty_paranoia_check(tty, inode, __func__)) return 0; @@ -1785,7 +1786,11 @@ int tty_release(struct inode *inode, struct file *filp) __func__, tty_name(tty, buf)); tty_unlock_pair(tty, o_tty); mutex_unlock(&tty_mutex); - schedule(); + schedule_timeout_killable(timeout); + if (timeout < 120 * HZ) + timeout = 2 * timeout + 1; + else + timeout = MAX_SCHEDULE_TIMEOUT; } /* -- 2.1.3 -- 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/