Add Serialized SSH Administrative Console

src/admin_command_gate.c

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* Shared recursive gate for administrative command execution origins. */
+
+#include "admin_command_gate.h"
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/semphr.h"
+
+static portMUX_TYPE s_lock = portMUX_INITIALIZER_UNLOCKED;
+static SemaphoreHandle_t s_gate;
+
+esp_err_t admin_command_gate_take(void)
+{
+    taskENTER_CRITICAL(&s_lock);
+    SemaphoreHandle_t gate = s_gate;
+    taskEXIT_CRITICAL(&s_lock);
+    if (gate == NULL) {
+        SemaphoreHandle_t candidate = xSemaphoreCreateRecursiveMutex();
+        if (candidate == NULL) {
+            return ESP_ERR_NO_MEM;
+        }
+        taskENTER_CRITICAL(&s_lock);
+        if (s_gate == NULL) {
+            s_gate = candidate;
+            candidate = NULL;
+        }
+        gate = s_gate;
+        taskEXIT_CRITICAL(&s_lock);
+        if (candidate != NULL) {
+            vSemaphoreDelete(candidate);
+        }
+    }
+    return xSemaphoreTakeRecursive(gate, portMAX_DELAY) == pdTRUE ? ESP_OK : ESP_FAIL;
+}
+
+void admin_command_gate_give(void)
+{
+    taskENTER_CRITICAL(&s_lock);
+    SemaphoreHandle_t gate = s_gate;
+    taskEXIT_CRITICAL(&s_lock);
+    if (gate != NULL) {
+        (void)xSemaphoreGiveRecursive(gate);
+    }
+}