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-Tag: v2.6.32.64~15 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=26967a02542d7e0673f82bc1b71e467f37e0f858;p=thirdparty%2Fkernel%2Fstable.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: Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 37b164578826406a173ca7c20d9ba7430134d23e) Signed-off-by: Willy Tarreau --- diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index 123cedf62ccef..cbdd1698c07b8 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -1482,6 +1482,7 @@ void tty_release_dev(struct file *filp) int devpts; int idx; char buf[64]; + long timeout = 0; struct inode *inode; inode = filp->f_path.dentry->d_inode; @@ -1602,7 +1603,11 @@ void tty_release_dev(struct file *filp) printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue " "active!\n", tty_name(tty, buf)); mutex_unlock(&tty_mutex); - schedule(); + schedule_timeout_killable(timeout); + if (timeout < 120 * HZ) + timeout = 2 * timeout + 1; + else + timeout = MAX_SCHEDULE_TIMEOUT; } /*