[SERIAL] 8250: sysrq deadlock fix
Fix http://bugzilla.kernel.org/show_bug.cgi?id=6716
Doing a sysrq over a serial line into an SMP machine presently deadlocks.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 5443fcd..0ae9ced 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2252,10 +2252,14 @@
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
@@ -2277,7 +2281,8 @@
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)