[Linuxsampler-devel] Thread changes

[Christian S. <sch...@li...>]

Hi guys,

I've been working on fixing some dead locks that were occurring once in a 
while. The problem was that threads were restarted while holding mutex 
lock(s), which inevitably leads to dead locks even if the thread resumes later 
on.

To address this, I changed the way all thread loops work in LS, which 
basically is now:

int SomeThread::Main() {
	while (true) {
		// custom & safe cancellation point for thread
		TestCancel();

		// prevent thread from being cancelled
		// (e.g. to prevent deadlocks while holding a mutex lock)
		pushCanelable(false);

		// enter critical section involving locks and syscalls, e.g.:
		mutex.Lock();
		doSomeWork();
		usleep(100); //NOTE: defined as cancellation point by POSIX!
		mutex.Unlock();

		// now allow thread being cancelled again
		popCancelable();
	}
}

So threads use now "well defined", safe cancellation points. Accordingly the 
code base now relies on pthread_testcancel() being available, and if it is 
avilable then threads are no longer created as being asynchronously 
cancellable.

Since this meant quite a bunch of sensible changes, please let me know if 
things start to hang somewhere!

CU
Christian