From: Peter Hurley Date: Thu, 16 Oct 2014 17:51:30 +0000 (-0400) Subject: tty: Fix high cpu load if tty is unreleaseable X-Git-Tag: v3.4.106~42 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=26bc3aa52a38602cc5a4430571d90e158430573b;p=thirdparty%2Fkernel%2Fstable.git 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: Zefan Li --- diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index b28d6356a142c..2d66beed3e1fd 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; } /*