On Tue, Oct 10, 2017 at 09:56:26AM -0700, Linus Torvalds wrote:
> So I think the best model would be something like this:
>
> - T1:
> mutex_lock(&lock)
> ...
> mutex_transfer(&lock)
>
> - T2:
> mutex_receive(&lock);
> ...
> mutex_unlock(&lock);
>
> where the "mutex_transfer() -> mutex_receive()" thing really makes it
> obvious that "now thread 1 is transferring the lock to thread 2".
Ah, but that's not at all what cross-release is about. Nobody really
does wonky ownership transfer of mutexes like that (although there might
be someone doing something with semaphores, I didn't check). Its to
allow detecting this deadlock:
mutex_lock(&lock)
wait_for_completion(&c);
mutex_lock(&lock);
complete(&c);
The completion doesn't have an owner to transfer.
