This is a note to let you know that I've just added the patch titled tty: Fix high cpu load if tty is unreleaseable to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-next branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will also be merged in the next major kernel release during the merge window. If you have any questions about this process, please let me know. >From 37b164578826406a173ca7c20d9ba7430134d23e Mon Sep 17 00:00:00 2001 From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> Date: Thu, 16 Oct 2014 13:51:30 -0400 Subject: 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: <stable@xxxxxxxxxxxxxxx> # since before 2.6.32 Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 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; } /* -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html