MQTT进行publish的时候好像比较容易出现问题，这样改似乎有改善，仅供参考。

ESP8266_RTOS_SDK/third_party/mqtt/library/MQTTClient.c
ESP8266_RTOS_SDK/third_party/mqtt/platform/MQTTFreeRTOS.c

diff --git a/ESP8266_RTOS_SDK/third_party/mqtt/library/MQTTClient.c b/ESP8266_RTOS_SDK/third_party/mqtt/library/MQTTClient.c
index e21af51..937beba 100755
--- a/ESP8266_RTOS_SDK/third_party/mqtt/library/MQTTClient.c
+++ b/ESP8266_RTOS_SDK/third_party/mqtt/library/MQTTClient.c
@@ -251,6 +251,8 @@ void MQTTCloseSession(MQTTClient* c)
     c->isconnected = 0;
     if (c->cleansession)
         MQTTCleanSession(c);
+
+    c->ipstack->disconnect(c->ipstack);
 }
 
 
@@ -345,7 +347,7 @@ int MQTTYield(MQTTClient* c, int timeout_ms)
 
     TimerInit(&timer);
     TimerCountdownMS(&timer, timeout_ms);
-
+#if 0
    do
     {
         if (cycle(c, &timer) < 0)
@@ -354,6 +356,20 @@ int MQTTYield(MQTTClient* c, int timeout_ms)
             break;
         }
    } while (!TimerIsExpired(&timer));
+#else
+#if defined(MQTT_TASK)
+    MutexLock(&c->mutex);
+#endif
+
+    if (cycle(c, &timer) < 0)
+    {
+        rc = FAILURE;
+    }
+
+#if defined(MQTT_TASK)
+    MutexUnlock(&c->mutex);
+#endif
+#endif
 
     return rc;
 }

diff --git a/ESP8266_RTOS_SDK/third_party/mqtt/platform/MQTTFreeRTOS.c b/ESP8266_RTOS_SDK/third_party/mqtt/platform/MQTTFreeRTOS.c
index 1cd3999..ee5ad92 100755
--- a/ESP8266_RTOS_SDK/third_party/mqtt/platform/MQTTFreeRTOS.c
+++ b/ESP8266_RTOS_SDK/third_party/mqtt/platform/MQTTFreeRTOS.c
@@ -38,19 +38,22 @@ int ThreadStart(Thread* thread, void (*fn)(void*), void* arg)
 
 void MutexInit(Mutex* mutex)
 {
-    mutex->sem = xSemaphoreCreateMutex();
+    //mutex->sem = xSemaphoreCreateMutex();
+    mutex->sem = xSemaphoreCreateRecursiveMutex();
 }
 
 
 int MutexLock(Mutex* mutex)
 {
-    return xSemaphoreTake(mutex->sem, portMAX_DELAY);
+    //return xSemaphoreTake(mutex->sem, portMAX_DELAY);
+    return xSemaphoreTakeRecursive(mutex->sem, portMAX_DELAY);
 }
 
 
 int MutexUnlock(Mutex* mutex)
 {
-    return xSemaphoreGive(mutex->sem);
+    //return xSemaphoreGive(mutex->sem);
+    return xSemaphoreGiveRecursive(mutex->sem);
 }
 
 void TimerCountdownMS(Timer* timer, unsigned int timeout_ms)