On Tue, May 02, 2006 at 03:09:43PM +0100, Alan Cox wrote:
> Russell got various bits of mail showing the 8250 console fix broke some
> setups with the assumptions it made. Based on this suggestion that we
> actually need to just do the locking I've prepared an alternative
> patch.
I had merged your suggestion this morning, though I've just redone it
to fix a bug.
> There are two questions that I think make this an RFC not a final patch
>
> 1. Should this be pushed up into serial/serial_core.c for all chips.
No - uart_console_write doesn't know enough about the hardware to be
able to take the spinlock itself.
> 2. Is the use of local_irq_save/spin_trylock spin_unlock_irqrestore
> going to break any platforms that do weird stuff or do we need a
> spin_trylock_irqsave ?
We do have a spin_trylock_irqsave(), so we don't need to worry about this.
b41d859ea4471c8784c500b97cdf82c7529c19ee
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2235,10 +2235,17 @@ static void
serial8250_console_write(struct console *co, const char *s, unsigned int count)
{
struct uart_8250_port *up = &serial8250_ports[co->index];
+ unsigned long flags;
unsigned int ier;
+ int locked = 1;
touch_nmi_watchdog();
+ if (oops_in_progress) {
+ locked = spin_trylock_irqsave(&up->port.lock, flags);
+ } else
+ spin_lock_irqsave(&up->port.lock, flags);
+
/*
* First save the IER then disable the interrupts
*/
@@ -2257,6 +2265,9 @@ serial8250_console_write(struct console
*/
wait_for_xmitr(up, BOTH_EMPTY);
serial_out(up, UART_IER, ier);
+
+ if (locked)
+ spin_unlock_irqrestore(&up->port.lock, flags);
}
static int serial8250_console_setup(struct console *co, char *options)
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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