PATCH: Minimal fix for sysrq on serial console hang

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

When I originally did this change I used oops_in_progress as a locking
guide. However it turns out there is one other place that turns all the
locking on its head and that is sysrq.

The fix below is a minimal fix to avoid this hanging and worst case may
lead to the very rare stuck character as it did pre 2.6.16 anyway but
only when using sysrq [which right now hangs the box]

The right fix is probably to unlock on the sysrq path and relock and
reconfigure the uart but thats more complex and not low risk at this
point in time although I will revisit it after (or during KS/OLS)
depending on rmk's view.

Signed-off-by: Alan Cox <alan@redhat.com>

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.18-rc1/drivers/serial/8250.c linux-2.6.18-rc1/drivers/serial/8250.c
--- linux.vanilla-2.6.18-rc1/drivers/serial/8250.c	2006-07-12 12:16:47.000000000 +0100
+++ linux-2.6.18-rc1/drivers/serial/8250.c	2006-07-12 12:21:10.000000000 +0100
@@ -2240,10 +2240,12 @@
 
 	touch_nmi_watchdog();
 
-	if (oops_in_progress) {
-		locked = spin_trylock_irqsave(&up->port.lock, flags);
-	} else
-		spin_lock_irqsave(&up->port.lock, flags);
+	/*
+	 *	This can occur during an oops, in which case we want to
+	 *	do our best, or sysrq which is hairier and eventually needs
+	 *	a nicer solution
+	 */
+	locked = spin_trylock_irqsave(&up->port.lock, flags);
 
 	/*
 	 *	First save the IER then disable the interrupts

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/