From 4ef0466578f84f6ba3e67204e450606d65ef88d0 Mon Sep 17 00:00:00 2001
From: Christopher Pascoe <alltheblinkythings@gmail.com>
Date: Tue, 29 Dec 2015 12:05:15 -0500
Subject: [PATCH] Don't trip the WDT if interrupts are disabled during write()
 or flush().

Prior to this change, if interrupts were disabled during a call to
HardwareSerial::write() when the circular buffer was full, or
HardwareSerial::flush() when the circular buffer was non-empty,
we would loop forever and trip a watchdog timeout.
---
 cores/esp8266/HardwareSerial.cpp | 6 ++++++
 cores/esp8266/interrupts.h       | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/cores/esp8266/HardwareSerial.cpp b/cores/esp8266/HardwareSerial.cpp
index 3fd5af48b..b0f6861d2 100644
--- a/cores/esp8266/HardwareSerial.cpp
+++ b/cores/esp8266/HardwareSerial.cpp
@@ -636,6 +636,9 @@ void HardwareSerial::flush() {
             if(_tx_buffer->getSize() == 0 &&
                UART_GET_TX_FIFO_ROOM(uart_nr) >= UART_TX_FIFO_SIZE) {
                 break;
+            } else if(il.savedInterruptLevel() > 0) {
+                _tx_empty_irq();
+                continue;
             }
         }
         yield();
@@ -663,6 +666,9 @@ size_t HardwareSerial::write(uint8_t c) {
                 break;
             } else if(_tx_buffer->write(c)) {
                 break;
+            } else if(il.savedInterruptLevel() > 0) {
+                _tx_empty_irq();
+                continue;
             }
         }
         yield();
diff --git a/cores/esp8266/interrupts.h b/cores/esp8266/interrupts.h
index 813997447..b4a2ed44b 100644
--- a/cores/esp8266/interrupts.h
+++ b/cores/esp8266/interrupts.h
@@ -31,6 +31,10 @@ public:
         xt_wsr_ps(_state);
     }
 
+    uint32_t savedInterruptLevel() const {
+        return _state & 0x0f;
+    }
+
 protected:
     uint32_t _state;
 };