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@vger.kernel.org> # since before 2.6.32
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 16a2c02..4021c10 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1709,6 +1709,7 @@
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 @@
__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;
}
/*