From: Alan Cox <alan@linux.intel.com>
Subject: [PATCH] tty_port: handle the nonblocking open of a dead port corner
	case
To: greg@kroah.com, linux-kernel@vger.kernel.org
Date: Wed, 18 Nov 2009 14:12:58 +0000
Message-ID: <20091118141254.3304.85805.stgit@localhost.localdomain>
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Some drivers allow O_NDELAY of a dead port (eg for setserial to work). In that
situation we must not try to raise the carrier.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable@kernel.org
---

 drivers/char/tty_port.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)


diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index da12fae..5e2ac57 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -241,8 +241,11 @@ int tty_port_block_til_ready(struct tty_port *port,
 
 	/* if non-blocking mode is set we can pass directly to open unless
 	   the port has just hung up or is in another error state */
-	if ((filp->f_flags & O_NONBLOCK) ||
-			(tty->flags & (1 << TTY_IO_ERROR))) {
+	if (tty->flags & (1 << TTY_IO_ERROR)) {
+		port->flags |= ASYNC_NORMAL_ACTIVE;
+		return 0;
+	}
+	if (filp->f_flags & O_NONBLOCK) {
 		/* Indicate we are open */
 		if (tty->termios->c_cflag & CBAUD)
 			tty_port_raise_dtr_rts(port);

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