Merge branch 'bugfix/uart_tx_done_timeout_check' into 'master'

donghengqaz · donghengqaz · commit 911e2d7aa7ec · 2021-04-28T11:39:26.000Z
fix(uart): potential blocking code when call uart_wait_tx_done()

See merge request sdk/ESP8266_RTOS_SDK!1599
diff --git a/components/esp8266/driver/uart.c b/components/esp8266/driver/uart.c
@@ -257,7 +257,18 @@ esp_err_t uart_wait_tx_done(uart_port_t uart_num, TickType_t ticks_to_wait)
     uint32_t baudrate;
     uint32_t byte_delay_us = 0;
     BaseType_t res;
+    portTickType ticks_cur;
+    portTickType ticks_start = xTaskGetTickCount();
     portTickType ticks_end = xTaskGetTickCount() + ticks_to_wait;
+    /**
+     *  Considering the overflow of the ticks_end and the ticks_cur (xTaskGetTickCount()),
+     *  the possible tick timestamp is as follows:
+    *   (one start tick timestamp, two end tick timestamps, four current tick timestamps)
+     *
+     * ticks: 0                                                               0xFFFFFFFF
+     *        |_______._______._______._______._______._______._______._______|
+     *               cur1    end1    cur2   start    cur3    end2    cur4
+    */
 
     // Take tx_mux
     res = xSemaphoreTake(p_uart_obj[uart_num]->tx_mux, (portTickType)ticks_to_wait);
@@ -273,10 +284,22 @@ esp_err_t uart_wait_tx_done(uart_port_t uart_num, TickType_t ticks_to_wait)
     uart_get_baudrate(uart_num, &baudrate);
     byte_delay_us = (uint32_t)(10000000 / baudrate); // (1/baudrate)*10*1000_000 us
 
-    ticks_to_wait = ticks_end - xTaskGetTickCount();
+    ticks_cur = xTaskGetTickCount();
+    if (ticks_start <= ticks_cur) {
+        ticks_to_wait = ticks_to_wait - (ticks_cur - ticks_start);
+    } else {
+        ticks_to_wait = ticks_to_wait - (portMAX_DELAY - ticks_start + ticks_cur);
+    }
     // wait for tx done sem.
     if (pdTRUE == xSemaphoreTake(p_uart_obj[uart_num]->tx_done_sem, ticks_to_wait)) {
         while (1) {
+            ticks_cur = xTaskGetTickCount();
+            bool end1_timeout = (ticks_end < ticks_start && ticks_cur < ticks_start && ticks_cur > ticks_end);
+            bool end2_timeout = (ticks_start < ticks_end && (ticks_cur < ticks_start || ticks_end < ticks_cur));
+            if (end1_timeout || end2_timeout) {
+                xSemaphoreGive(p_uart_obj[uart_num]->tx_mux);
+                return ESP_ERR_TIMEOUT;
+            }
             if (UART[uart_num]->status.txfifo_cnt == 0) {
                 ets_delay_us(byte_delay_us); // Delay one byte time to guarantee transmission completion 
                 break;
