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// SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#include <mutex>
#include "common/assert.h"
#include "common/fiber.h"
#include "common/virtual_buffer.h"
#include <boost/context/detail/fcontext.hpp>
namespace Common {
constexpr std::size_t default_stack_size = 512 * 1024;
struct Fiber::FiberImpl {
FiberImpl() : stack{default_stack_size}, rewind_stack{default_stack_size} {}
VirtualBuffer<u8> stack;
VirtualBuffer<u8> rewind_stack;
std::mutex guard;
std::function<void()> entry_point;
std::function<void()> rewind_point;
std::shared_ptr<Fiber> previous_fiber;
bool is_thread_fiber{};
bool released{};
u8* stack_limit{};
u8* rewind_stack_limit{};
boost::context::detail::fcontext_t context{};
boost::context::detail::fcontext_t rewind_context{};
};
void Fiber::SetRewindPoint(std::function<void()>&& rewind_func) {
impl->rewind_point = std::move(rewind_func);
}
void Fiber::Start(boost::context::detail::transfer_t& transfer) {
ASSERT(impl->previous_fiber != nullptr);
impl->previous_fiber->impl->context = transfer.fctx;
impl->previous_fiber->impl->guard.unlock();
impl->previous_fiber.reset();
impl->entry_point();
UNREACHABLE();
}
void Fiber::OnRewind([[maybe_unused]] boost::context::detail::transfer_t& 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;
impl->rewind_point();
UNREACHABLE();
}
void Fiber::FiberStartFunc(boost::context::detail::transfer_t transfer) {
auto* fiber = static_cast<Fiber*>(transfer.data);
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()>&& entry_point_func) : impl{std::make_unique<FiberImpl>()} {
impl->entry_point = std::move(entry_point_func);
impl->stack_limit = impl->stack.data();
impl->rewind_stack_limit = impl->rewind_stack.data();
u8* stack_base = impl->stack_limit + default_stack_size;
impl->context =
boost::context::detail::make_fcontext(stack_base, impl->stack.size(), FiberStartFunc);
}
Fiber::Fiber() : impl{std::make_unique<FiberImpl>()} {}
Fiber::~Fiber() {
if (impl->released) {
return;
}
// Make sure the Fiber is not being used
const bool locked = impl->guard.try_lock();
ASSERT_MSG(locked, "Destroying a fiber that's still running");
if (locked) {
impl->guard.unlock();
}
}
void Fiber::Exit() {
ASSERT_MSG(impl->is_thread_fiber, "Exitting non main thread fiber");
if (!impl->is_thread_fiber) {
return;
}
impl->guard.unlock();
impl->released = true;
}
void Fiber::Rewind() {
ASSERT(impl->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::weak_ptr<Fiber> weak_from, Fiber& to) {
to.impl->guard.lock();
to.impl->previous_fiber = weak_from.lock();
auto transfer = boost::context::detail::jump_fcontext(to.impl->context, &to);
// "from" might no longer be valid if the thread was killed
if (auto from = weak_from.lock()) {
if (from->impl->previous_fiber == nullptr) {
ASSERT_MSG(false, "previous_fiber is nullptr!");
return;
}
from->impl->previous_fiber->impl->context = transfer.fctx;
from->impl->previous_fiber->impl->guard.unlock();
from->impl->previous_fiber.reset();
}
}
std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
std::shared_ptr<Fiber> fiber = std::shared_ptr<Fiber>{new Fiber()};
fiber->impl->guard.lock();
fiber->impl->is_thread_fiber = true;
return fiber;
}
} // namespace Common
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