From 47358929e29790bbedcb4dd4dec18f1e166b896f Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Fri, 21 Dec 2012 09:09:15 +1100
Subject: [PATCH] HAL_AVR: fixed attach_interrupt race condition

---
 libraries/AP_HAL_AVR/GPIO.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libraries/AP_HAL_AVR/GPIO.cpp b/libraries/AP_HAL_AVR/GPIO.cpp
index e40e1fdd62..ca4acc00f7 100644
--- a/libraries/AP_HAL_AVR/GPIO.cpp
+++ b/libraries/AP_HAL_AVR/GPIO.cpp
@@ -97,9 +97,12 @@ bool AVRGPIO::attach_interrupt(
         uint8_t interrupt_num, AP_HAL::Proc proc, uint8_t mode) {
     if (!((mode == 0)||(mode == 1)||(mode==3))) return false;
     if (interrupt_num == 6) {
+	uint8_t oldSREG = SREG;
+	cli();	
         _interrupt_6 = proc;
         EICRB = (EICRB & ~((1 << ISC60) | (1 << ISC61))) | (mode << ISC60);
         EIMSK |= (1 << INT6);
+	SREG = oldSREG;
         return true;
     } else {
         return false;