thread cancel_blocking usage, kernels

The Genode book suggests that an RPC caller can protect itself from blocking in a stalled server by creating a watchdog thread to monitor the process of the call, and cancel it if it takes too long.

Is there a robust/canonical example of using cancel_blocking in this way?

My experiment with this (Genode 17.08, x86_32) seems to work as expected--but, only with the OKL4 kernel!? With nova, hw, and seL4, the cancel_blocking() method executes but seemingly to no effect: the thread continues to wait on the (contrived) very slow RPC call, which eventually completes.

Suggestions?

// Steve Harp