From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750929AbWGQQbl (ORCPT ); Mon, 17 Jul 2006 12:31:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750931AbWGQQbl (ORCPT ); Mon, 17 Jul 2006 12:31:41 -0400 Received: from mail.kroah.org ([69.55.234.183]:19642 "EHLO perch.kroah.org") by vger.kernel.org with ESMTP id S1750928AbWGQQbk (ORCPT ); Mon, 17 Jul 2006 12:31:40 -0400 Date: Mon, 17 Jul 2006 09:29:34 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org, rmk@arm.linux.org.uk Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , torvalds@osdl.org, akpm@osdl.org, alan@lxorguk.ukuu.org.uk, enrico.scholz@informatik.tu-chemnitz.de, Greg Kroah-Hartman Subject: [patch 44/45] serial 8250: sysrq deadlock fix Message-ID: <20060717162934.GS4829@kroah.com> References: <20060717160652.408007000@blue.kroah.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="serial-8250-sysrq-deadlock-fix.patch" In-Reply-To: <20060717162452.GA4829@kroah.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org -stable review patch. If anyone has any objections, please let us know. ------------------ From: Andrew Morton Fix http://bugzilla.kernel.org/show_bug.cgi?id=6716 Doing a sysrq over a serial line into an SMP machine presently deadlocks. Cc: Russell King Cc: Enrico Scholz Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- drivers/serial/8250.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- linux-2.6.17.6.orig/drivers/serial/8250.c +++ linux-2.6.17.6/drivers/serial/8250.c @@ -2241,10 +2241,14 @@ serial8250_console_write(struct console touch_nmi_watchdog(); - if (oops_in_progress) { - locked = spin_trylock_irqsave(&up->port.lock, flags); + local_irq_save(flags); + if (up->port.sysrq) { + /* serial8250_handle_port() already took the lock */ + locked = 0; + } else if (oops_in_progress) { + locked = spin_trylock(&up->port.lock); } else - spin_lock_irqsave(&up->port.lock, flags); + spin_lock(&up->port.lock); /* * First save the IER then disable the interrupts @@ -2266,7 +2270,8 @@ serial8250_console_write(struct console serial_out(up, UART_IER, ier); if (locked) - spin_unlock_irqrestore(&up->port.lock, flags); + spin_unlock(&up->port.lock); + local_irq_restore(flags); } static int serial8250_console_setup(struct console *co, char *options) --