From d5e370a4eeb701201bd441b4ec089091dd6f2ce0 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Wed, 5 Nov 2014 12:12:54 -0500 Subject: [PATCH] tty: Don't release tty locks for wait queue sanity check Releasing the tty locks while waiting for the tty wait queues to be empty is no longer necessary nor desirable. Prior to "tty: Don't take tty_mutex for tty count changes", dropping the tty locks was necessary to reestablish the correct lock order between tty_mutex and the tty locks. Dropping the global tty_mutex was necessary; otherwise new ttys could not have been opened while waiting. However, without needing the global tty_mutex held, the tty locks for the releasing tty can now be held through the sleep. The sanity check is for abnormal conditions caused by kernel bugs, not for recoverable errors caused by misbehaving userspace; dropping the tty locks only allows the tty state to get more sideways. Reviewed-by: Alan Cox Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index e59de81c39a9..b008e2b38d54 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1798,13 +1798,10 @@ int tty_release(struct inode *inode, struct file *filp) * first, its count will be one, since the master side holds an open. * Thus this test wouldn't be triggered at the time the slave closes, * so we do it now. - * - * Note that it's possible for the tty to be opened again while we're - * flushing out waiters. By recalculating the closing flags before - * each iteration we avoid any problems. */ + tty_lock_pair(tty, o_tty); + while (1) { - tty_lock_pair(tty, o_tty); tty_closing = tty->count <= 1; o_tty_closing = o_tty && (o_tty->count <= (pty_master ? 1 : 0)); @@ -1835,7 +1832,6 @@ int tty_release(struct inode *inode, struct file *filp) printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", __func__, tty_name(tty, buf)); - tty_unlock_pair(tty, o_tty); schedule(); } -- 2.34.1