releases/2.6.22.2/fix-deadlocks-in-sparc-serial-console.patch

From stable-bounces@linux.kernel.org Wed Jul 18 02:34:14 2007
From: David Miller <davem@davemloft.net>
Date: Wed, 18 Jul 2007 02:34:05 -0700 (PDT)
Subject: Fix deadlocks in sparc serial console.
To: stable@kernel.org
Cc: bunk@stusta.de
Message-ID: <20070718.023405.58454422.davem@davemloft.net>


From: David S. Miller <davem@davemloft.net>

Subject: [PATCH] [SERIAL]: Fix console write locking in sparc drivers.

Mirror the logic in 8250 for proper console write locking
when SYSRQ is triggered or an OOPS is in progress.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/serial/sunhv.c    |   30 ++++++++++++++++++++++++++----
 drivers/serial/sunsab.c   |   19 ++++++++++++++-----
 drivers/serial/sunsu.c    |   14 ++++++++++++++
 drivers/serial/sunzilog.c |   17 ++++++++++++++---
 4 files changed, 68 insertions(+), 12 deletions(-)

--- a/drivers/serial/sunhv.c
+++ b/drivers/serial/sunhv.c
@@ -440,8 +440,16 @@ static void sunhv_console_write_paged(st
 {
 	struct uart_port *port = sunhv_port;
 	unsigned long flags;
+	int locked = 1;
+
+	local_irq_save(flags);
+	if (port->sysrq) {
+		locked = 0;
+	} else if (oops_in_progress) {
+		locked = spin_trylock(&port->lock);
+	} else
+		spin_lock(&port->lock);
 
-	spin_lock_irqsave(&port->lock, flags);
 	while (n > 0) {
 		unsigned long ra = __pa(con_write_page);
 		unsigned long page_bytes;
@@ -469,7 +477,10 @@ static void sunhv_console_write_paged(st
 			ra += written;
 		}
 	}
-	spin_unlock_irqrestore(&port->lock, flags);
+
+	if (locked)
+		spin_unlock(&port->lock);
+	local_irq_restore(flags);
 }
 
 static inline void sunhv_console_putchar(struct uart_port *port, char c)
@@ -488,7 +499,15 @@ static void sunhv_console_write_bychar(s
 {
 	struct uart_port *port = sunhv_port;
 	unsigned long flags;
-	int i;
+	int i, locked = 1;
+
+	local_irq_save(flags);
+	if (port->sysrq) {
+		locked = 0;
+	} else if (oops_in_progress) {
+		locked = spin_trylock(&port->lock);
+	} else
+		spin_lock(&port->lock);
 
 	spin_lock_irqsave(&port->lock, flags);
 	for (i = 0; i < n; i++) {
@@ -496,7 +515,10 @@ static void sunhv_console_write_bychar(s
 			sunhv_console_putchar(port, '\r');
 		sunhv_console_putchar(port, *s++);
 	}
-	spin_unlock_irqrestore(&port->lock, flags);
+
+	if (locked)
+		spin_unlock(&port->lock);
+	local_irq_restore(flags);
 }
 
 static struct console sunhv_console = {
--- a/drivers/serial/sunsab.c
+++ b/drivers/serial/sunsab.c
@@ -860,22 +860,31 @@ static int num_channels;
 static void sunsab_console_putchar(struct uart_port *port, int c)
 {
 	struct uart_sunsab_port *up = (struct uart_sunsab_port *)port;
-	unsigned long flags;
-
-	spin_lock_irqsave(&up->port.lock, flags);
 
 	sunsab_tec_wait(up);
 	writeb(c, &up->regs->w.tic);
-
-	spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static void sunsab_console_write(struct console *con, const char *s, unsigned n)
 {
 	struct uart_sunsab_port *up = &sunsab_ports[con->index];
+	unsigned long flags;
+	int locked = 1;
+
+	local_irq_save(flags);
+	if (up->port.sysrq) {
+		locked = 0;
+	} else if (oops_in_progress) {
+		locked = spin_trylock(&up->port.lock);
+	} else
+		spin_lock(&up->port.lock);
 
 	uart_console_write(&up->port, s, n, sunsab_console_putchar);
 	sunsab_tec_wait(up);
+
+	if (locked)
+		spin_unlock(&up->port.lock);
+	local_irq_restore(flags);
 }
 
 static int sunsab_console_setup(struct console *con, char *options)
--- a/drivers/serial/sunsu.c
+++ b/drivers/serial/sunsu.c
@@ -1288,7 +1288,17 @@ static void sunsu_console_write(struct c
 				unsigned int count)
 {
 	struct uart_sunsu_port *up = &sunsu_ports[co->index];
+	unsigned long flags;
 	unsigned int ier;
+	int locked = 1;
+
+	local_irq_save(flags);
+	if (up->port.sysrq) {
+		locked = 0;
+	} else if (oops_in_progress) {
+		locked = spin_trylock(&up->port.lock);
+	} else
+		spin_lock(&up->port.lock);
 
 	/*
 	 *	First save the UER then disable the interrupts
@@ -1304,6 +1314,10 @@ static void sunsu_console_write(struct c
 	 */
 	wait_for_xmitr(up);
 	serial_out(up, UART_IER, ier);
+
+	if (locked)
+		spin_unlock(&up->port.lock);
+	local_irq_restore(flags);
 }
 
 /*
--- a/drivers/serial/sunzilog.c
+++ b/drivers/serial/sunzilog.c
@@ -9,7 +9,7 @@
  * C. Dost, Pete Zaitcev, Ted Ts'o and Alex Buell for their
  * work there.
  *
- *  Copyright (C) 2002, 2006 David S. Miller (davem@davemloft.net)
+ * Copyright (C) 2002, 2006, 2007 David S. Miller (davem@davemloft.net)
  */
 
 #include <linux/module.h>
@@ -1151,11 +1151,22 @@ sunzilog_console_write(struct console *c
 {
 	struct uart_sunzilog_port *up = &sunzilog_port_table[con->index];
 	unsigned long flags;
+	int locked = 1;
+
+	local_irq_save(flags);
+	if (up->port.sysrq) {
+		locked = 0;
+	} else if (oops_in_progress) {
+		locked = spin_trylock(&up->port.lock);
+	} else
+		spin_lock(&up->port.lock);
 
-	spin_lock_irqsave(&up->port.lock, flags);
 	uart_console_write(&up->port, s, count, sunzilog_putchar);
 	udelay(2);
-	spin_unlock_irqrestore(&up->port.lock, flags);
+
+	if (locked)
+		spin_unlock(&up->port.lock);
+	local_irq_restore(flags);
 }
 
 static int __init sunzilog_console_setup(struct console *con, char *options)