From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755912Ab2IIXdM (ORCPT ); Sun, 9 Sep 2012 19:33:12 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51185 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755269Ab2IIXQK (ORCPT ); Sun, 9 Sep 2012 19:16:10 -0400 Message-Id: <20120909224202.893071204@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 09 Sep 2012 23:43:20 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jason Wessel , Alan Cox , Greg Kroah-Hartman Subject: [ 90/95] pmac_zilog,kdb: Fix console poll hook to return instead of loop In-Reply-To: <20120909224150.641491654@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jason Wessel commit 38f8eefccf3a23c4058a570fa2938a4f553cf8e0 upstream. kdb <-> kgdb transitioning does not work properly with this UART driver because the get character routine loops indefinitely as opposed to returning NO_POLL_CHAR per the expectation of the KDB I/O driver API. The symptom is a kernel hang when trying to switch debug modes. Cc: Alan Cox Signed-off-by: Jason Wessel Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/tty/serial/pmac_zilog.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c index 654755a..333c8d0 100644 --- a/drivers/tty/serial/pmac_zilog.c +++ b/drivers/tty/serial/pmac_zilog.c @@ -1348,10 +1348,16 @@ static int pmz_verify_port(struct uart_port *port, struct serial_struct *ser) static int pmz_poll_get_char(struct uart_port *port) { struct uart_pmac_port *uap = (struct uart_pmac_port *)port; + int tries = 2; - while ((read_zsreg(uap, R0) & Rx_CH_AV) == 0) - udelay(5); - return read_zsdata(uap); + while (tries) { + if ((read_zsreg(uap, R0) & Rx_CH_AV) != 0) + return read_zsdata(uap); + if (tries--) + udelay(5); + } + + return NO_POLL_CHAR; } static void pmz_poll_put_char(struct uart_port *port, unsigned char c)