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-Url: http://git.lede-project.org./?a=commitdiff_plain;h=37b164578826406a173ca7c20d9ba7430134d23e;p=openwrt%2Fstaging%2Fblogic.git tty: Fix high cpu load if tty is unreleaseable 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: # since before 2.6.32 Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 16a2c0237dd6..4021c10d9908 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1709,6 +1709,7 @@ 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; @@ -1793,7 +1794,11 @@ 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; } /*