From a1fd207aee9da2b5044e2974497d82290d476601 Mon Sep 17 00:00:00 2001
From: Darian Leung <darian@espressif.com>
Date: Fri, 27 Mar 2020 17:58:12 +0800
Subject: [PATCH] Add Task Watchdog backtrace printing

This commit makes the Task Watchdog print the backtrace of both
cores when it times out.
---
 components/esp32/crosscore_int.c             |  9 +++++++++
 components/esp32/include/esp_crosscore_int.h | 10 ++++++++++
 components/esp32/task_wdt.c                  | 15 ++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/components/esp32/crosscore_int.c b/components/esp32/crosscore_int.c
index 407157e4a1..1130c28de1 100644
--- a/components/esp32/crosscore_int.c
+++ b/components/esp32/crosscore_int.c
@@ -18,6 +18,7 @@
 #include "esp_err.h"
 #include "esp_intr.h"
 #include "esp_intr_alloc.h"
+#include "esp_panic.h"
 
 #include "rom/ets_sys.h"
 #include "rom/uart.h"
@@ -36,6 +37,7 @@
 
 #define REASON_YIELD            BIT(0)
 #define REASON_FREQ_SWITCH      BIT(1)
+#define REASON_PRINT_BACKTRACE  BIT(2)
 
 static portMUX_TYPE reason_spinlock = portMUX_INITIALIZER_UNLOCKED;
 static volatile uint32_t reason[ portNUM_PROCESSORS ];
@@ -76,6 +78,9 @@ static void IRAM_ATTR esp_crosscore_isr(void *arg) {
          * to allow DFS features without the extra latency of the ISR hook.
          */
     }
+    if (my_reason_val & REASON_PRINT_BACKTRACE) {
+        esp_backtrace_print(100);
+    }
 }
 
 //Initialize the crosscore interrupt on this core. Call this once
@@ -117,3 +122,7 @@ void IRAM_ATTR esp_crosscore_int_send_freq_switch(int core_id)
     esp_crosscore_int_send(core_id, REASON_FREQ_SWITCH);
 }
 
+void IRAM_ATTR esp_crosscore_int_send_print_backtrace(int core_id)
+{
+    esp_crosscore_int_send(core_id, REASON_PRINT_BACKTRACE);
+}
diff --git a/components/esp32/include/esp_crosscore_int.h b/components/esp32/include/esp_crosscore_int.h
index 2f1c5b3bec..41ddd7a707 100644
--- a/components/esp32/include/esp_crosscore_int.h
+++ b/components/esp32/include/esp_crosscore_int.h
@@ -51,4 +51,14 @@ void esp_crosscore_int_send_yield(int core_id);
  */
 void esp_crosscore_int_send_freq_switch(int core_id);
 
+/**
+ * Send an interrupt to a CPU indicating it should print its current backtrace
+ * 
+ * This is use internally by the Task Watchdog to dump the backtrace of the
+ * opposite core and should not be called from application code.
+ * 
+ * @param core_id Core that should print its backtrace
+ */
+void esp_crosscore_int_send_print_backtrace(int core_id);
+
 #endif
diff --git a/components/esp32/task_wdt.c b/components/esp32/task_wdt.c
index 0c302082a4..abb4868f57 100644
--- a/components/esp32/task_wdt.c
+++ b/components/esp32/task_wdt.c
@@ -28,6 +28,7 @@
 #include "esp_intr.h"
 #include "esp_intr_alloc.h"
 #include "esp_attr.h"
+#include "esp_panic.h"
 #include "esp_freertos_hooks.h"
 #include "soc/timer_group_struct.h"
 #include "soc/timer_group_reg.h"
@@ -36,6 +37,7 @@
 #include "driver/periph_ctrl.h"
 #include "esp_task_wdt.h"
 #include "esp_system_internal.h"
+#include "esp_crosscore_int.h"
 
 static const char *TAG = "task_wdt";
 
@@ -167,13 +169,24 @@ static void task_wdt_isr(void *arg)
     }
 
     esp_task_wdt_isr_user_handler();
+
     if (twdt_config->panic){     //Trigger Panic if configured to do so
         ESP_EARLY_LOGE(TAG, "Aborting.");
         portEXIT_CRITICAL_ISR(&twdt_spinlock);
         esp_reset_reason_set_hint(ESP_RST_TASK_WDT);
         abort();
+    } else {
+        int current_core = xPortGetCoreID();
+        //Print backtrace of current core
+        ESP_EARLY_LOGE(TAG, "Print CPU %d (current core) backtrace", current_core);
+        esp_backtrace_print(100);
+    #if !CONFIG_FREERTOS_UNICORE
+        //Print backtrace of other core
+        ESP_EARLY_LOGE(TAG, "Print CPU %d backtrace", !current_core);
+        esp_crosscore_int_send_print_backtrace(!current_core);
+    #endif
     }
-
+    
     portEXIT_CRITICAL_ISR(&twdt_spinlock);
 }