From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934537AbbA1EZI (ORCPT ); Tue, 27 Jan 2015 23:25:08 -0500 Received: from mail.kernel.org ([198.145.29.136]:40900 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965174AbbA1EY6 (ORCPT ); Tue, 27 Jan 2015 23:24:58 -0500 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Hurley , Greg Kroah-Hartman , Zefan Li Subject: [PATCH 3.4 140/177] tty: Fix high cpu load if tty is unreleaseable Date: Wed, 28 Jan 2015 12:09:58 +0800 Message-Id: <1422418236-12852-231-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Hurley 3.4.106-rc1 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: Greg Kroah-Hartman Signed-off-by: Zefan Li --- 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 b28d635..2d66beed 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1633,6 +1633,7 @@ int tty_release(struct inode *inode, struct file *filp) int devpts; int idx; char buf[64]; + long timeout = 0; if (tty_paranoia_check(tty, inode, __func__)) return 0; @@ -1717,7 +1718,11 @@ int tty_release(struct inode *inode, struct file *filp) __func__, 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; } /* -- 1.9.1