freertos: mark port_xSchedulerRunning as volatile

components/freertos/xtensa/port.c

@@ -151,7 +151,7 @@ static const char* TAG = "cpu_start"; // [refactor-todo]: might be appropriate t
 _Static_assert(tskNO_AFFINITY == CONFIG_FREERTOS_NO_AFFINITY, "incorrect tskNO_AFFINITY value");
 
 /*-----------------------------------------------------------*/
-unsigned port_xSchedulerRunning[portNUM_PROCESSORS] = {0}; // Duplicate of inaccessible xSchedulerRunning; needed at startup to avoid counting nesting
+volatile unsigned port_xSchedulerRunning[portNUM_PROCESSORS] = {0}; // Duplicate of inaccessible xSchedulerRunning; needed at startup to avoid counting nesting
 unsigned port_interruptNesting[portNUM_PROCESSORS] = {0};  // Interrupt nesting level. Increased/decreased in portasm.c, _frxt_int_enter/_frxt_int_exit
 BaseType_t port_uxCriticalNesting[portNUM_PROCESSORS] = {0};
 BaseType_t port_uxOldInterruptState[portNUM_PROCESSORS] = {0};