Hmm that did not work. I think I did it right:

#define SIGSTOP SIGUSR1

Reader:

            struct sigaction sa;

  & nbsp;         sigemptyset(&sa.sa_mask);

            sa.sa_handler = sig_handler;

            sa.sa_flags = 0;

            int status  = sigaction(SIGSTOP, &sa, NULL);

            sio_fd = open("/dev/ttyS1", O_RDONLY);.

.

.

            uint8_t c;

            while (_tcb ->theventset == noEvents ) {

                        if (sizeof(c) == read(sio_fd,&c,sizeof(c))) {

                                    yada

                        }

            }

Task stop

                          uint32_t flags = irqsave();

             & nbsp;          _tcb->theventset |= ExitRequest;

                          irqrestore(flags);

                          pthread_kill(_tcb->thread,SIGSTOP);

&nbsp ;

…. The issue is was in uart_read it never returned. I looked at it was waiting one a semaphore in a loop. And the loop did not exit

David