rw_mutex condition_variable deadlock

[BrettRToomey]

Hello, I understand that Linux is not currently supported, but I just wanted to point this out and ask if there's any way I could help.

raddebugger/src/os/core/linux/os_core_linux.c

Lines 943 to 958 in 9ec7fb6

	// TODO(rjf): because pthread does not supply cv/rw natively, I had to hack
	// this together, but this would probably just be a lot better if we just
	// implemented the primitives ourselves with e.g. futexes
	//
	if(os_handle_match(cv, os_handle_zero())) { return 0; }
	if(os_handle_match(mutex_rw, os_handle_zero())) { return 0; }
	OS_LNX_Entity *cv_entity = (OS_LNX_Entity *)cv.u64[0];
	OS_LNX_Entity *rw_mutex_entity = (OS_LNX_Entity *)mutex_rw.u64[0];
	struct timespec endt_timespec;
	endt_timespec.tv_sec = endt_us/Million(1);
	endt_timespec.tv_nsec = Thousand(1) * (endt_us - (endt_us/Million(1))*Million(1));
	B32 result = 0;
	for(;;)
	{
	pthread_mutex_lock(&cv_entity->cv.rwlock_mutex_handle);
	int wait_result = pthread_cond_timedwait(&cv_entity->cv.cond_handle, &cv_entity->cv.rwlock_mutex_handle, &endt_timespec);

On line 958, there's a wait on the cv's rw-workaround-mutex, but the thread still holds the reader lock. If this reader is waiting on a writer to publish results, like in the task system, the writer won't ever be able to publish.

Unless I'm mistaken, a way around this would be to unlock the reader lock after taking the rw-workaround-mutex. Then I think the rw-workaround-mutex would also have to be locked before signalling and broadcasting.

I see in your comment above that you would like to replace this with a futex and I was wondering if this was something I could contribute? Were you planning on implementing a condition variable or was there something smarter/simpler than that?

On a personal project I have ported your OS layer and Render layer to macOS and Metal hoping that if/when you look into macOS I can seed this project with an initial implementation. I understand that right now this is just noise and I have no expectation that you will want it merged in, but if you're interested please let me know and I can publish my efforts.