fix(log_router): ensure mutex is created successfully, or else return an error

Check if the mutex (which ensures thread safety) was created
successfully, and return an error if it wasn't. Moved this check to the
top of the <<>> function, so that it doesn't need to clean up allocated
memory.

Since successfully creating the mutex is now a precondition for creating
the list, we can safely remove the NULL checks when using the mutex.

Author: Vincent-Dalstra

components/utilities/log_router/log_router.c

@@ -118,9 +118,7 @@ int esp_log_router_flash_vprintf(const char *format, va_list args)
     }
 
     // Lock mutex for thread safety
-    if (g_log_router_mutex) {
-        xSemaphoreTake(g_log_router_mutex, portMAX_DELAY);
-    }
+    xSemaphoreTake(g_log_router_mutex, portMAX_DELAY);
 
     // Write to all files that match the log level
     esp_log_router_slist_t *item;
@@ -244,9 +242,7 @@ int esp_log_router_flash_vprintf(const char *format, va_list args)
     }
 
     // Release mutex
-    if (g_log_router_mutex) {
-        xSemaphoreGive(g_log_router_mutex);
-    }
+    xSemaphoreGive(g_log_router_mutex);
 
     return ret;
 }
@@ -290,6 +286,13 @@ static void esp_log_router_shutdown(void)
 
 esp_err_t esp_log_router_to_file(const char* file_path, const char* tag, esp_log_level_t level)
 {
+    // Create mutex for thread safety
+    g_log_router_mutex = xSemaphoreCreateMutex();
+    if (g_log_router_mutex == NULL) {
+        ESP_LOGW(TAG, "Failed to create mutex for log router");
+        return ESP_ERR_NO_MEM;
+    }
+
     if (!file_path) {
         return ESP_ERR_INVALID_ARG;
     }
@@ -376,12 +379,6 @@ esp_err_t esp_log_router_to_file(const char* file_path, const char* tag, esp_log
         SLIST_INSERT_HEAD(&g_esp_log_router_slist_head, new_log_router, next);
         g_esp_log_router_vprintf = esp_log_set_vprintf(esp_log_router_flash_vprintf);
         esp_register_shutdown_handler(esp_log_router_shutdown);
-
-        // Create mutex for thread safety when first node is added
-        g_log_router_mutex = xSemaphoreCreateMutex();
-        if (g_log_router_mutex == NULL) {
-            ESP_LOGW(TAG, "Failed to create mutex for log router");
-        }
     } else {
         // Find the last node and insert after it
         esp_log_router_slist_t *last = SLIST_FIRST(&g_esp_log_router_slist_head);