diff --git a/portable/ThirdParty/GCC/Posix/port.c b/portable/ThirdParty/GCC/Posix/port.c
index 7cc32128f6..c4eacb2ba6 100644
--- a/portable/ThirdParty/GCC/Posix/port.c
+++ b/portable/ThirdParty/GCC/Posix/port.c
@@ -105,6 +105,8 @@ static BaseType_t xSchedulerEnd = pdFALSE;
 static pthread_t hTimerTickThread;
 static bool xTimerTickThreadShouldRun;
 static uint64_t prvStartTimeNs;
+static pthread_mutex_t xThreadMutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_key_t xThreadKey = 0;
 /*-----------------------------------------------------------*/
 
 static void prvSetupSignalsAndSchedulerPolicy( void );
@@ -119,6 +121,45 @@ static void vPortStartFirstTask( void );
 static void prvPortYieldFromISR( void );
 /*-----------------------------------------------------------*/
 
+void prvThreadKeyDestructor( void * data )
+{
+    free( data );
+}
+
+static void prvInitThreadKey()
+{
+    pthread_mutex_lock( &xThreadMutex );
+
+    if( xThreadKey == 0 )
+    {
+        pthread_key_create( &xThreadKey, prvThreadKeyDestructor );
+    }
+
+    pthread_mutex_unlock( &xThreadMutex );
+}
+
+static void prvMarkAsFreeRTOSThread( pthread_t thread )
+{
+    prvInitThreadKey();
+    uint8_t * thread_data = malloc( 1 );
+    configASSERT( thread_data != NULL );
+    *thread_data = 1;
+    pthread_setspecific( xThreadKey, thread_data );
+}
+
+static BaseType_t prvIsFreeRTOSThread( pthread_t thread )
+{
+    uint8_t * thread_data = ( uint8_t * ) pthread_getspecific( xThreadKey );
+
+    return thread_data != NULL && *thread_data == 1;
+}
+
+static void prvDestroyThreadKey()
+{
+    pthread_key_delete( xThreadKey );
+}
+/*-----------------------------------------------------------*/
+
 static void prvFatalError( const char * pcCall,
                            int iErrno ) __attribute__( ( __noreturn__ ) );
 
@@ -249,6 +290,8 @@ BaseType_t xPortStartScheduler( void )
     /* Restore original signal mask. */
     ( void ) pthread_sigmask( SIG_SETMASK, &xSchedulerOriginalSignalMask, NULL );
 
+    prvDestroyThreadKey();
+
     return 0;
 }
 /*-----------------------------------------------------------*/
@@ -266,8 +309,12 @@ void vPortEndScheduler( void )
     ( void ) pthread_kill( hMainThread, SIG_RESUME );
 
     /* Waiting to be deleted here. */
-    pxCurrentThread = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
-    event_wait( pxCurrentThread->ev );
+    if( prvIsFreeRTOSThread( pthread_self() ) == pdTRUE )
+    {
+        pxCurrentThread = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
+        event_wait( pxCurrentThread->ev );
+    }
+
     pthread_testcancel();
 }
 /*-----------------------------------------------------------*/
@@ -322,13 +369,19 @@ void vPortYield( void )
 
 void vPortDisableInterrupts( void )
 {
-    pthread_sigmask( SIG_BLOCK, &xAllSignals, NULL );
+    if( prvIsFreeRTOSThread( pthread_self() ) == pdTRUE )
+    {
+        pthread_sigmask(SIG_BLOCK, &xAllSignals, NULL);
+    }
 }
 /*-----------------------------------------------------------*/
 
 void vPortEnableInterrupts( void )
 {
-    pthread_sigmask( SIG_UNBLOCK, &xAllSignals, NULL );
+    if( prvIsFreeRTOSThread( pthread_self() ) == pdTRUE )
+    {
+        pthread_sigmask(SIG_UNBLOCK, &xAllSignals, NULL);
+    }
 }
 /*-----------------------------------------------------------*/
 
@@ -364,6 +417,8 @@ static void * prvTimerTickHandler( void * arg )
 {
     ( void ) arg;
 
+    prvMarkAsFreeRTOSThread( pthread_self() );
+
     prvPortSetCurrentThreadName("Scheduler timer");
 
     while( xTimerTickThreadShouldRun )
@@ -396,26 +451,31 @@ void prvSetupTimerInterrupt( void )
 
 static void vPortSystemTickHandler( int sig )
 {
-    Thread_t * pxThreadToSuspend;
-    Thread_t * pxThreadToResume;
+    if( prvIsFreeRTOSThread( pthread_self() ) == pdTRUE )
+    {
+        Thread_t * pxThreadToSuspend;
+        Thread_t * pxThreadToResume;
 
-    ( void ) sig;
+        ( void ) sig;
 
-    uxCriticalNesting++; /* Signals are blocked in this signal handler. */
+        uxCriticalNesting++; /* Signals are blocked in this signal handler. */
 
-    pxThreadToSuspend = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
+        pxThreadToSuspend = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
 
-    if( xTaskIncrementTick() != pdFALSE )
-    {
-        /* Select Next Task. */
-        vTaskSwitchContext();
+        if( xTaskIncrementTick() != pdFALSE )
+        {
+            /* Select Next Task. */
+            vTaskSwitchContext();
 
-        pxThreadToResume = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
+            pxThreadToResume = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
 
-        prvSwitchThread( pxThreadToResume, pxThreadToSuspend );
-    }
+            prvSwitchThread( pxThreadToResume, pxThreadToSuspend );
+        }
 
-    uxCriticalNesting--;
+        uxCriticalNesting--;
+    } else {
+        fprintf( stderr, "vPortSystemTickHandler called from non-FreeRTOS thread\n" );
+    }
 }
 /*-----------------------------------------------------------*/
 
@@ -448,6 +508,8 @@ static void * prvWaitForStart( void * pvParams )
 {
     Thread_t * pxThread = pvParams;
 
+    prvMarkAsFreeRTOSThread( pthread_self() );
+
     prvSuspendSelf( pxThread );
 
     /* Resumed for the first time, unblocks all signals. */