async: add re_thread_async

[sreimers]

Usage:

re_thread_async(blocking_work, callback, data);

Example:

#include <re.h>

enum { JOBS = 100 };

static int cnt = 0;


static int work(void *arg)
{
	(void)arg;
	
	sys_msleep(10);
	
	return 0;
}


static void callback(int err, void *arg)
{
	(void)arg;
	(void)err;

	if (++cnt >= JOBS)
		re_cancel();
}


int main(void)
{
	libre_init();
	re_thread_async_init(16);

	for (int i = 0; i < JOBS; i++) {
		re_thread_async(work, callback, NULL);
	}

	re_main(NULL);

	re_thread_async_close();
	libre_close();
}

[cspiel1]

Would the RX RTP "real-time" thread in baresip one possible application for this new API?

[sreimers]

In first place I need it to make getaddrinfo or filesystem accesses async. But maybe its much easier with this new API, since the callback is executed by re main thread. Only the accessed data by work has to be thread-safe. Maybe its enough to make the heavy work async/multithreaded (video decoding for example).