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 the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-fix-high-cpu-load-if-tty-is-unreleaseable.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>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
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
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 <peter@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_io.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1686,6 +1686,7 @@ int tty_release(struct inode *inode, str
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;
@@ -1770,7 +1771,11 @@ int tty_release(struct inode *inode, str
__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;
}
/*
Patches currently in stable-queue which might be from peter@xxxxxxxxxxxxxxxxxx are
queue-3.17/tty-fix-high-cpu-load-if-tty-is-unreleaseable.patch
queue-3.17/serial-fix-divide-by-zero-fault-in-uart_get_divisor.patch
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