From 069347b245ac0afe052f68e7f5ea734207f826f4 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Thu, 16 Oct 2014 13:51:30 -0400 Subject: [PATCH] tty: Fix high cpu load if tty is unreleaseable 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(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 446df6b39d304..613f06a95176a 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1594,6 +1594,7 @@ 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, "tty_release_dev")) return 0; @@ -1721,7 +1722,11 @@ int tty_release(struct inode *inode, struct file *filp) "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; } /* -- 2.47.2