AsynPortDriver separate thread causes Segmentation fault with "dbGetLinkValue" error message

[Abdalla Ahmad via Tech-talk <tech-talk at aps.anl.gov>]

Hi

I am writing an AsynPortDriver class for the libera spark and I would like to do the waveforms data acquisition in a separate thread (attached is my initial implementation). Whenever a large data size requested (Using command "ADC 100" for example), the IOC crashes with the following message:

dbGetLinkValue: Illegal link type -13664

Segmentation fault

Noticing that this number is random at every time the IOC crashes. Right now I am trying to enable core dumps on my machine (for some reason they are not dumped), but in the meantime, what is wrong with my thread implementation?

Is it possible to have a variable length waveform record in EPICS? If yes, how does asyn implements this?

Best Regards,

Abdalla.

void LiberaSpark::performDAQ()
{
	printf("DAQ Thread initialized!\n");

	string line = "";
	char* command = (char*) "ADC 200\n";
	int status;
	ssize_t bytes;
	char buffer[48];
	struct pollfd polling_fds[1];

	polling_fds[0].fd = this->device_socket;
	polling_fds[0].events = POLLIN;
	polling_fds[0].revents = 0;
	while(true)
	{
		lock();
		pthread_mutex_lock(&device_mutex);

		bytes = write(device_socket, command, strlen(command));

		status = poll(polling_fds, 1, 1);
		int i = 0;
		while(status > 0)
		{
			memset(buffer, 0, sizeof(buffer));
			bytes = read(device_socket, buffer, sizeof(buffer));
			buffer[bytes - 1] = '\0';
			stringstream ss(buffer);
			cout << ss.str() << endl;
			while(ss >> line)
			{
				if(i % 4 == 0)
					adc_a[i / 4] = atoi(line.c_str());
				i++;
			}
			status = poll(polling_fds, 1, 1);
		}
	
		pthread_mutex_unlock(&device_mutex);
		unlock();
		sleep(1);
	}
}