Index: linux-2.6-kgdb/drivers/tty/serial/8250.c
===================================================================
--- linux-2.6-kgdb.orig/drivers/tty/serial/8250.c	2011-07-28 09:07:06.313204001 -0500
+++ linux-2.6-kgdb/drivers/tty/serial/8250.c	2011-07-28 09:21:43.363203854 -0500
@@ -38,6 +38,7 @@
 #include <linux/nmi.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/kdb.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -2894,10 +2895,14 @@
 
 	touch_nmi_watchdog();
 
-	if (up->port.sysrq || oops_in_progress)
-		locked = spin_trylock_irqsave(&up->port.lock, flags);
-	else
-		spin_lock_irqsave(&up->port.lock, flags);
+	if (unlikely(in_kdb_printk())) {
+		locked = 0;
+	} else {
+		if (up->port.sysrq || 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
Index: linux-2.6-kgdb/include/linux/kdb.h
===================================================================
--- linux-2.6-kgdb.orig/include/linux/kdb.h	2011-07-28 09:09:55.523204135 -0500
+++ linux-2.6-kgdb/include/linux/kdb.h	2011-07-28 09:12:21.183204000 -0500
@@ -153,12 +153,14 @@
 extern int kdb_register_repeat(char *, kdb_func_t, char *, char *,
 			       short, kdb_repeat_t);
 extern int kdb_unregister(char *);
+#define in_kdb_printk() (kdb_trap_printk)
 #else /* ! CONFIG_KGDB_KDB */
 #define kdb_printf(...)
 #define kdb_init(x)
 #define kdb_register(...)
 #define kdb_register_repeat(...)
 #define kdb_uregister(x)
+#define in_kdb_printk() (0)
 #endif	/* CONFIG_KGDB_KDB */
 enum {
 	KDB_NOT_INITIALIZED,
Index: linux-2.6-kgdb/kernel/debug/kdb/kdb_io.c
===================================================================
--- linux-2.6-kgdb.orig/kernel/debug/kdb/kdb_io.c	2011-07-28 09:05:40.963204003 -0500
+++ linux-2.6-kgdb/kernel/debug/kdb/kdb_io.c	2011-07-28 09:13:02.463204337 -0500
@@ -539,7 +539,6 @@
 	int diag;
 	int linecount;
 	int logging, saved_loglevel = 0;
-	int saved_trap_printk;
 	int got_printf_lock = 0;
 	int retlen = 0;
 	int fnd, len;
@@ -550,8 +549,6 @@
 	unsigned long uninitialized_var(flags);
 
 	preempt_disable();
-	saved_trap_printk = kdb_trap_printk;
-	kdb_trap_printk = 0;
 
 	/* Serialize kdb_printf if multiple cpus try to write at once.
 	 * But if any cpu goes recursive in kdb, just print the output,
@@ -807,7 +804,6 @@
 	} else {
 		__release(kdb_printf_lock);
 	}
-	kdb_trap_printk = saved_trap_printk;
 	preempt_enable();
 	return retlen;
 }
@@ -817,9 +813,11 @@
 	va_list ap;
 	int r;
 
+	kdb_trap_printk++;
 	va_start(ap, fmt);
 	r = vkdb_printf(fmt, ap);
 	va_end(ap);
+	kdb_trap_printk--;
 
 	return r;
 }