From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753176AbbHaOeX (ORCPT ); Mon, 31 Aug 2015 10:34:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48042 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752755AbbHaOeU (ORCPT ); Mon, 31 Aug 2015 10:34:20 -0400 From: Vitaly Kuznetsov To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Dexuan Cui Subject: [PATCH] serial: core: prevent softlockups on slow consoles Date: Mon, 31 Aug 2015 16:34:16 +0200 Message-Id: <1441031656-17959-1-git-send-email-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hyper-V serial port is very slow on multi-vCPU guest, this causes soflockups on intensive console writes. Touch nmi watchdog after putting every char on port to avoid the issue for all serial drivers, the overhead should be small. This is just a part of the fix: serial8250_console_write() disables irqs for all its execution time (which on such slow consoles can be dozens of seconds), it should be possible to observe devices being stuck on this CPU. We need to find a better way, e.g. do output in batches enabling irqs in between. Signed-off-by: Vitaly Kuznetsov --- drivers/tty/serial/serial_core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index f368520..cc05785 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -33,7 +33,7 @@ #include /* for serial_state and serial_icounter_struct */ #include #include -#include +#include #include #include @@ -1792,6 +1792,7 @@ void uart_console_write(struct uart_port *port, const char *s, if (*s == '\n') putchar(port, '\r'); putchar(port, *s); + touch_nmi_watchdog(); } } EXPORT_SYMBOL_GPL(uart_console_write); -- 2.4.3