cb7b5ddd25
Every sched_algorithm_with_properties<PROPS> subclass awakened() call must ensure that control reaches sched_algorithm_with_properties<PROPS>::awakened() _before_ any logic in the subclass method attempts to access properties. This turns out to be all too easy to forget. So instead, advise subclasses to overrride new awakened_props() method. Base- class method sets things up and then calls awakened_props(). Moreover, when the compiler supports it, sched_algorithm_with_properties<PROPS>::awakened() is now marked 'final' to remind subclass authors to override awakened_props() instead.
boost.fiber
boost.fiber provides a framework for micro-/userland-threads (fibers) scheduled cooperativly. The API contains classes and functions to manage and synchronize fibers similiar to boost.thread.
A fiber is able to store the current execution state, including all registers and CPU flags, the instruction pointer, and the stack pointer and later restore this state. The idea is to have multiple execution paths running on a single thread using a sort of cooperative scheduling (threads are preemptively scheduled) - the running fiber decides explicitly when its yields to allow another fiber to run (context switching).
A context switch between threads costs usally thousends of CPU cycles on x86 compared to a fiber switch with less than 100 cycles. A fiber can only run on a single thread at any point in time.
Building: Detailed instructions can be found at https://svn.boost.org/trac/boost/wiki/TryModBoost.