debug_core,kdb: Allow the debug core to process a recursive debug entry

This allows kdb to debug a crash with in the kms code with a
single level recursive re-entry.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

kernel/debug/debug_core.c

@@ -445,6 +445,10 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
 	}
 
 	printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
+#ifdef CONFIG_KGDB_KDB
+	/* Allow kdb to debug itself one level */
+	return 0;
+#endif
 	dump_stack();
 	panic("Recursive entry to debugger");
 
@@ -489,6 +493,9 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
 	 */
 	atomic_inc(&cpu_in_kgdb[cpu]);
 
+	if (exception_level == 1)
+		goto cpu_master_loop;
+
 	/*
 	 * CPU will loop if it is a slave or request to become a kgdb
 	 * master cpu and acquire the kgdb_active lock: