Specificaly, remove access methods in worker_fiber, fiber and this_fiber.
thread_affinity is not used by any present library code. It was intended for
use by workstealing user sched_algorithm implementations. The properties
mechanism is a better way to address scheduler-specific properties.
Change waiting_queue::head_ from worker_fiber* to fiber_base* for uniformity
with worker_fiber::nxt_. This lets push() scan from head_ with a fiber_base**,
looking for the right insertion point. Insertion then becomes a couple
unconditional assignments.
Because push() always scans from head_, tail_ was actually never used. Remove
it.
Maintaining a singly-linked list is tricky when you walk it with a node*
pointer. But if you use a node** pointer starting at &head_ and advancing to
point to each &nxt_ pointer, you can coalesce the empty-list case into the
normal case.
Some reviewers disliked that to build a custom sched_algorithm subclass, you
must necessarily manipulate pointers to classes in the boost::fibers::detail
namespace. Redefine all such methods to use fiber_base* rather than
detail::worker_fiber*.
Hoist fiber_base* into boost::fibers namespace. We considered an opaque
typedef rather than fiber_base*, but in fact a sched_algorithm subclass may
need is_ready().
Moreover, a sched_algorithm subclass may well want to use an intrusive linked
list to queue fibers. Hoist worker_fiber::nxt_ pointer into fiber_base, and
remove worker_fiber::next() and next_reset() methods. This allows recasting
detail::fifo in terms of fiber_base*, therefore round_robin can be stated
almost entirely in terms of fiber_base* rather than worker_fiber*.
Recast fiber constructor taking worker_fiber* to take fiber_base* instead.
This constructor is used solely for fiber migration; with relevant functions
now returning fiber_base*, we think we no longer need fiber(worker_fiber*).
Instead of setting a fiber_properties subclass's sched_algo_ back pointer once
at construction time, unconditionally set it every time that fiber becomes
READY (and is therefore passed to sched_algorithm::awakened()). This handles
the case in which that fiber migrates to a different thread with a different
sched_algorithm subclass instance.
Break out fiber_properties::notify() implementation to a separate .cpp
implementation file so it can bring in algorithm.hpp. We don't want
properties.hpp to depend on algorithm.hpp.
Introduce fiber_properties class from which to derive a specific properties
class for a particular user-coded sched_algorithm subclass.
Add sched_algorithm::property_change(worker_fiber*, fiber_properties*) method
to allow a fiber_properties subclass method to notify the sched_algorithm
subclass of a change in a relevant property. This generalizes the present
priority() method.
Introduce sched_algorithm_with_properties<PROPS> template class from which to
derive a user-coded scheduler that uses fiber_properties subclass PROPS. Give
it ref-returning properties(fiber::id) and properties(worker_fiber*) methods.
Introduce fiber_properties* field in worker_fiber, and initialize it to 0.
Delete it when the worker_fiber is destroyed. Give it pointer-flavored access
methods. Normally this field will remain 0; but the first time the
worker_fiber is passed to a sched_algorithm_with_properties<PROPS> subclass,
its awakened() method will instantiate the relevant PROPS subclass.
Add ref-returning fiber::properties<PROPS>() method. Calling this method
presumes that the current thread's sched_algorithm is derived from
sched_algorithm_with_properties<PROPS>.
Also add this_fiber::properties<PROPS>() with the same restriction.
Add ref-returning fm_properties<PROPS>() functions to implement
fiber::properties<PROPS>() and this_fiber::properties<PROPS>().
Allow sched_algorithm_with_properties to extract the worker_fiber* from a
fiber::id (aka worker_fiber::id) so it can present public-facing
properties(id) method as well as properties(worker_fiber*) method.
(cherry picked from commit 18c7f2c13b9642826b42aa3f6fa0a6642fce9cbc)
Conflicts:
include/boost/fiber/detail/worker_fiber.hpp
include/boost/fiber/fiber_manager.hpp
scheduler and setting it with set_scheduling_algorithm(). Document
sched_algorithm interface class.
Fix the example in condition_variables.qbk to explicitly unlock 'lk'
before
calling process_data().
Add some explanatory material in scheduling.qbk about coding your own
scheduler and setting it with set_scheduling_algorithm(). Document
sched_algorithm interface class.
Fix the example in condition_variables.qbk to explicitly unlock 'lk' before
calling process_data().
