tty: Fix high cpu load if tty is unreleaseable
PATCH 1/1 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 <[email protected]> # since before 2.6.32
Signed-off-by Peter Hurley <[email protected]>
--- drivers/tty/tty_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
drivers/tty/tty_io.c +6 -1
@@ -1708,6 +1708,7 @@ 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 ;
@@ -1792,7 +1793,11 @@ 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 ; }/*
Signature · 1 line
2.1.1