Explicit context switch of fibers

[SerenGTI]

Hi there,
I am currently researching the behavior of non-blocking code such as boost::fiber under different scheduling mechanisms. One such mechanism is the symmetric transfer, wherein one fiber is suspended and another fiber is immediately resumed with no caller/callee relationship between the two.

Hence, I would like to explicitly resume a previously suspended fiber in the current thread, bypassing the scheduler. Assume I have a list of suspended fibers, represented by their contexts, for example as

std::deque<context*> suspended_contexts;

Now, in a running fiber, let's call it F, I would like to be able to yield F and then resume suspended_contexts.front() without passing control to any other fibers that may be in the scheduler's ready queue. However, I seem to be unable to get context->attach(), context->resume() or any other method used throughout the codebase to work.

I know that the scheduler realizes a context switch between fibers through

// resume another context
algo_->pick_next()->resume();

which essentially does

context::active()->attach(next_fiber_context);
next_fiber_context->resume();

however, when I use next_fiber_context = suspended_contexts.front(), my code deadlocks on the call to resume().

Am I missing something crucial about the fiber context switch?
Could you direct me to a more detailed documentation of a context switch as it is used in the library?

Moreover, is there a way to pass the suspended fiber F to the scheduler so that another thread may execute it in the meantime? A fiber must be explicitly enqueued into the scheduler's ready queue by calling awakened(ctx). Is it safe to do so with ctx = context::active()?