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Common/Fiber: Implement Rewind on Boost Context.

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This commit is contained in:
Fernando Sahmkow 2020-04-01 09:19:10 -04:00
parent 59ce6e6d06
commit b6655aa2e4
2 changed files with 39 additions and 2 deletions
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39
src/common/fiber.cpp
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@ -113,7 +113,11 @@ std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
struct Fiber::FiberImpl { struct Fiber::FiberImpl {
alignas(64) std::array<u8, default_stack_size> stack; alignas(64) std::array<u8, default_stack_size> stack;
u8* stack_limit;
alignas(64) std::array<u8, default_stack_size> rewind_stack;
u8* rewind_stack_limit;
boost::context::detail::fcontext_t context; boost::context::detail::fcontext_t context;
boost::context::detail::fcontext_t rewind_context;
}; };
void Fiber::start(boost::context::detail::transfer_t& transfer) { void Fiber::start(boost::context::detail::transfer_t& transfer) {
@ -125,21 +129,43 @@ void Fiber::start(boost::context::detail::transfer_t& transfer) {
UNREACHABLE(); UNREACHABLE();
} }
void Fiber::onRewind(boost::context::detail::transfer_t& [[maybe_unused]] transfer) {
ASSERT(impl->context != nullptr);
impl->context = impl->rewind_context;
impl->rewind_context = nullptr;
u8* tmp = impl->stack_limit;
impl->stack_limit = impl->rewind_stack_limit;
impl->rewind_stack_limit = tmp;
rewind_point(rewind_parameter);
UNREACHABLE();
}
void Fiber::FiberStartFunc(boost::context::detail::transfer_t transfer) { void Fiber::FiberStartFunc(boost::context::detail::transfer_t transfer) {
auto fiber = static_cast<Fiber*>(transfer.data); auto fiber = static_cast<Fiber*>(transfer.data);
fiber->start(transfer); fiber->start(transfer);
} }
void Fiber::RewindStartFunc(boost::context::detail::transfer_t transfer) {
auto fiber = static_cast<Fiber*>(transfer.data);
fiber->onRewind(transfer);
}
Fiber::Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter) Fiber::Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter)
: guard{}, entry_point{std::move(entry_point_func)}, start_parameter{start_parameter}, : guard{}, entry_point{std::move(entry_point_func)}, start_parameter{start_parameter},
previous_fiber{} { previous_fiber{} {
impl = std::make_unique<FiberImpl>(); impl = std::make_unique<FiberImpl>();
u8* stack_limit = impl->stack.data(); impl->stack_limit = impl->stack.data();
u8* stack_base = stack_limit + default_stack_size; impl->rewind_stack_limit = impl->rewind_stack.data();
u8* stack_base = impl->stack_limit + default_stack_size;
impl->context = impl->context =
boost::context::detail::make_fcontext(stack_base, impl->stack.size(), FiberStartFunc); boost::context::detail::make_fcontext(stack_base, impl->stack.size(), FiberStartFunc);
} }
void Fiber::SetRewindPoint(std::function<void(void*)>&& rewind_func, void* start_parameter) {
rewind_point = std::move(rewind_func);
rewind_parameter = start_parameter;
}
Fiber::Fiber() { Fiber::Fiber() {
impl = std::make_unique<FiberImpl>(); impl = std::make_unique<FiberImpl>();
} }
@ -161,6 +187,15 @@ void Fiber::Exit() {
guard.unlock(); guard.unlock();
} }
void Fiber::Rewind() {
ASSERT(rewind_point);
ASSERT(impl->rewind_context == nullptr);
u8* stack_base = impl->rewind_stack_limit + default_stack_size;
impl->rewind_context =
boost::context::detail::make_fcontext(stack_base, impl->stack.size(), RewindStartFunc);
boost::context::detail::jump_fcontext(impl->rewind_context, this);
}
void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) { void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) {
ASSERT_MSG(from != nullptr, "Yielding fiber is null!"); ASSERT_MSG(from != nullptr, "Yielding fiber is null!");
ASSERT_MSG(to != nullptr, "Next fiber is null!"); ASSERT_MSG(to != nullptr, "Next fiber is null!");

2
src/common/fiber.h
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@ -70,8 +70,10 @@ private:
static void FiberStartFunc(void* fiber_parameter); static void FiberStartFunc(void* fiber_parameter);
static void RewindStartFunc(void* fiber_parameter); static void RewindStartFunc(void* fiber_parameter);
#else #else
void onRewind(boost::context::detail::transfer_t& transfer);
void start(boost::context::detail::transfer_t& transfer); void start(boost::context::detail::transfer_t& transfer);
static void FiberStartFunc(boost::context::detail::transfer_t transfer); static void FiberStartFunc(boost::context::detail::transfer_t transfer);
static void RewindStartFunc(boost::context::detail::transfer_t transfer);
#endif #endif
struct FiberImpl; struct FiberImpl;