From 44896b17f1c2d8824250e06bd07d7b5a4b7e6be4 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Thu, 6 Jul 2006 23:59:50 -0700 Subject: 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. 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(-) diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index bbf78aaf9e01..3863eba67984 100644 --- a/drivers/serial/8250.c +++ b/drivers/serial/8250.c @@ -2241,10 +2241,14 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count) 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 *co, const char *s, unsigned int count) 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) -- cgit v1.2.3