From 32303a9130def171462e39aad3b1b0ebe0ec0b1f Mon Sep 17 00:00:00 2001
From: Russ Butler <russ.butler@arm.com>
Date: Mon, 2 Oct 2017 19:32:20 -0500
Subject: [PATCH] Fix sleep lock underflow in LowPowerTimer

If a LowPowerTimer is started and then goes out of scope then a
deep sleep lock underflow can occur. This is because the
the variable '_lock_deepsleep' is checked when starting the timer
but is not checked in the destructor, which unconditionally releases
the deep sleep lock.
---
 drivers/Timer.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/Timer.cpp b/drivers/Timer.cpp
index 5da9863d95..f523974e6b 100644
--- a/drivers/Timer.cpp
+++ b/drivers/Timer.cpp
@@ -35,7 +35,9 @@ Timer::Timer(const ticker_data_t *data) : _running(), _start(), _time(), _ticker
 Timer::~Timer() {
     core_util_critical_section_enter();
     if (_running) {
-        sleep_manager_unlock_deep_sleep();
+        if(_lock_deepsleep) {
+            sleep_manager_unlock_deep_sleep();
+        }
     }
     _running = 0;
     core_util_critical_section_exit();