Return-Path: Message-Id: <20141116215330.102407774@1wt.eu> Date: Sun, 16 Nov 2014 22:54:03 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Peter Hurley , Greg Kroah-Hartman , Willy Tarreau Subject: [ 35/48] tty: Fix high cpu load if tty is unreleaseable In-Reply-To: <28c765bc23bd4bae1611534e510f49f8@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley 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. Cc: Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 37b164578826406a173ca7c20d9ba7430134d23e) Signed-off-by: Willy Tarreau --- drivers/char/tty_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index 123cedf..cbdd169 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -1482,6 +1482,7 @@ void tty_release_dev(struct file *filp) int devpts; int idx; char buf[64]; + long timeout = 0; struct inode *inode; inode = filp->f_path.dentry->d_inode; @@ -1602,7 +1603,11 @@ void tty_release_dev(struct file *filp) printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue " "active!\n", tty_name(tty, buf)); mutex_unlock(&tty_mutex); - schedule(); + schedule_timeout_killable(timeout); + if (timeout < 120 * HZ) + timeout = 2 * timeout + 1; + else + timeout = MAX_SCHEDULE_TIMEOUT; } /* -- 1.7.12.2.21.g234cd45.dirty