Archivist
/
PublicBin
1
0
Bifurcation 0
Code Tickets 0 Demandes d'ajout 0 Versions 0 Wiki Activité
A bunch of random code samples
Vous ne pouvez pas sélectionner plus de 25 sujets Les noms de sujets doivent commencer par une lettre ou un nombre, peuvent contenir des tirets ('-') et peuvent comporter jusqu'à 35 caractères.
3 Révisions
1 Branche
48 KiB
 
Aborescence: 98bbefa622
Branches Tags
${ item.name }
Créer la branche ${ searchTerm }
de '98bbefa622'
${ noResults }
PublicBin/less_minimal_scheduler.cpp

469 lignes
12 KiB
Brut Annotations Historique

// Build with: clang++ --std=c++20 -g -O1 schedtest.cpp
#include <array>
#include <span>
#include <memory>
#include <list>
#include <functional>
#include <iostream>
#include <map>
#include <chrono>
#include <exception>
#include <atomic>
#include <set>
#include <vector>
#include <optional>
#if defined(__x86_64__)
#if defined(__GNUG__)
constexpr bool is_x86_64_linux = true;
#else
#if defined(__clang__)
constexpr bool is_x86_64_linux = true;
#else
constexpr bool is_x86_64_linux = false;
#endif
#endif
#else
constexpr bool is_x86_64_linux = false;
#endif
static_assert(is_x86_64_linux, "This code probably only works on x86_64 GNU Extensions C++");
struct platform_data {
platform_data() = default;
platform_data(std::span<char> stack_str)
: stack_ptr(&*(stack_str.end()-16))
, base_ptr(stack_ptr)
{}
uint64_t rbx, r12, r13, r14, r15;
void* stack_ptr;
void* base_ptr;
void pull() __attribute__((always_inline))
{
__asm__ __volatile__(
"movq %%rsp, %0\n"
"movq %%rbp, %1\n"
"movq %%rbx, %2\n"
"movq %%r12, %3\n"
"movq %%r13, %4\n"
"movq %%r14, %5\n"
"movq %%r15, %6\n"
: "=m"(stack_ptr)
, "=m"(base_ptr)
, "=m"(rbx)
, "=m"(r12)
, "=m"(r13)
, "=m"(r14)
, "=m"(r15)
);
}
void* push(void* location) __attribute__((always_inline))
{
volatile void* volatile tmp = static_cast<char*>(stack_ptr) - sizeof(void*);
*static_cast<volatile void* volatile * volatile>(tmp) = location;
__asm__ __volatile__(
"movq %1, %%rsp\n"
"movq %2, %%rbp\n"
"movq %3, %%rbx\n"
"movq %4, %%r12\n"
"movq %5, %%r13\n"
"movq %6, %%r14\n"
"movq %7, %%r15\n"
"popq %0\n"
: "+r"(location)
: "m"(tmp)
, "m"(base_ptr)
, "m"(rbx)
, "m"(r12)
, "m"(r13)
, "m"(r14)
, "m"(r15)
: "memory"
);
return location;
}
};
enum class process_status {
inactive = 0,
running = 1,
waiting = 2,
finished = 3,
zombie = 4
};
struct process {
static int64_t counter;
char* stack;
size_t sz;
platform_data scheduling_swapper;
process_status state = process_status::inactive;
std::function<void()> fn;
int64_t t_id;
process(std::function<void()> _fn, size_t _sz = 16384)
: stack(new char[_sz])
, sz(_sz)
, scheduling_swapper(std::span<char>(stack, sz))
, fn(_fn)
, t_id(counter++)
{}
process(char* stack_base)
: stack(stack_base)
, sz(0)
, t_id(counter++)
{}
process(const process&) = delete;
~process() {
if(sz) delete[] stack;
}
};
int64_t process::counter = 0;
__attribute__((noinline)) struct system* spawner (struct system* sys);
struct system {
static system sys;
std::list<std::unique_ptr<process>>
running,
waiting,
naughty;
std::unique_ptr<process> previous;
std::unique_ptr<process> current;
std::unique_ptr<process> one() {
auto v = std::move(running.back());
running.pop_back();
return v;
}
void rid(std::unique_ptr<process> current) {
switch(current->state) {
case process_status::inactive:
case process_status::running:
running.push_front(std::move(current));
break;
case process_status::finished:
clean(std::move(current));
break;
case process_status::zombie:
naughty.push_front(std::move(current));
break;
case process_status::waiting:
waiting.push_front(std::move(current));
break;
}
}
void clean(std::unique_ptr<process>) {}
void yield_to(std::unique_ptr<process> target) noexcept {
current->scheduling_swapper.pull();
sys.rid(std::move(current));
current = std::move(target);
current->scheduling_swapper.push(this);
spawner(&sys);
}
void yield() noexcept {
current->scheduling_swapper.pull();
sys.rid(std::move(current));
current = one();
current->scheduling_swapper.push(this);
spawner(&sys);
}
template<typename fn>
void steal_and_yield(fn func) noexcept {
current->scheduling_swapper.pull();
func(std::move(current));
current = one();
current->scheduling_swapper.push(this);
spawner(&sys);
}
};
// Needs to return the system one way or another
__attribute__((noinline)) struct system* spawner (struct system* sys) {
auto& proc = *system::sys.current;
if(proc.state == process_status::inactive) {
proc.state = process_status::running;
proc.fn();
proc.state = process_status::finished;
sys->current->scheduling_swapper.pull();
sys->yield();
}
return sys;
}
struct system system::sys;
/********************* ***********************/
class dirty_bottleneck {
std::atomic_bool flag;
[[nodiscard]] bool try_lock() {
bool f = false;
bool t = true;
return flag.compare_exchange_strong(f,t,std::memory_order::acquire);
}
[[nodiscard]] bool try_unlock() {
bool f = false;
bool t = true;
return flag.compare_exchange_strong(t,f,std::memory_order::release);
}
public:
dirty_bottleneck() = default;
dirty_bottleneck(dirty_bottleneck&) = delete;
dirty_bottleneck(dirty_bottleneck&&) = delete;
void lock() {
while(not try_lock());
}
void unlock() {
if(!try_unlock()) throw std::runtime_error("Unlocking failed in dirty_bottleneck: potential double unlocking issue");
}
};
/********************* ***********************/
template<typename T>
class lock_guard {
T& ref;
public:
lock_guard(T& _ref)
: ref(_ref)
{
ref.lock();
}
~lock_guard() {
ref.unlock();
}
};
/********************* ***********************/
using mutex_handle = size_t;
enum class thread_state {
locking,
waiting,
unlocking
};
enum class mutex_state {
remove = 0,
create = 1
};
using namespace std::chrono_literals;
void mutex_state_update(mutex_handle, mutex_state);
void signal_locking(thread_state state, mutex_handle mtx, int64_t thrd);
class fast_bottleneck {
/** This is a secret tool that will help us later **/
static std::atomic<size_t> counter;
const mutex_handle handle;
dirty_bottleneck trigger_lock;
std::list<std::unique_ptr<process>> waiting;
std::atomic_bool flag;
[[nodiscard]] bool try_lock() {
bool f = false;
bool t = true;
return flag.compare_exchange_strong(f,t,std::memory_order::acquire);
}
[[nodiscard]] bool try_unlock() {
bool f = false;
bool t = true;
return flag.compare_exchange_strong(t,f,std::memory_order::release);
}
public:
fast_bottleneck()
: flag()
, handle(counter.fetch_add(1)) //< We have to initialize that
{
mutex_state_update(handle, mutex_state::create);
}
fast_bottleneck(fast_bottleneck&) = delete;
fast_bottleneck(fast_bottleneck&&) = delete;
fast_bottleneck& operator=(fast_bottleneck&) = delete;
fast_bottleneck& operator=(fast_bottleneck&&) = delete;
~fast_bottleneck() {
mutex_state_update(handle, mutex_state::remove);
}
void lock() {
/// The exponential backing variables
constexpr std::chrono::milliseconds max{1};
std::chrono::nanoseconds wait{256};
while(not try_lock()) {
/// The implementation of our little trick when waiting
signal_locking(thread_state::waiting, handle, system::sys.current->t_id);
system::sys.steal_and_yield([&](std::unique_ptr<process> p){
lock_guard triggers(trigger_lock);
p->state = process_status::waiting;
waiting.push_front(std::move(p));
});
/// The exponential backing
//std::this_thread::sleep_for(wait);
wait += wait < max ? std::chrono::nanoseconds(wait.count()/2) : 0ns;
}
/// The implementation of our little trick when locking
signal_locking(thread_state::locking, handle, system::sys.current->t_id);
}
void unlock() {
if(!try_unlock()) throw std::runtime_error("Unlocking failed in fast_bottleneck: potential double unlocking issue");
/// The implementation of our little trick when unlocking
signal_locking(thread_state::unlocking, handle, system::sys.current->t_id);
{
lock_guard triggers(trigger_lock);
if(waiting.size()) {
system::sys.running.push_front(std::move(waiting.back()));
waiting.pop_back();
}
}
}
};
dirty_bottleneck checker_lock;
dirty_bottleneck lister_lock;
std::map<int64_t, std::vector<mutex_handle>> owned_locks;
std::map<int64_t, std::optional<mutex_handle>> waiting_locks;
std::set<mutex_handle> locks_that_exist;
void mutex_state_update(mutex_handle mtx, mutex_state state) {
lock_guard lister(lister_lock);
switch(state) {
case mutex_state::create: {
locks_that_exist.insert(mtx);
}break;
case mutex_state::remove: {
locks_that_exist.erase(mtx);
}break;
}
}
bool build_dependency_graph (
const mutex_handle mtx,
const int64_t thrd,
std::map<int64_t, std::vector<mutex_handle>>& owned_locks,
std::map<int64_t, std::optional<mutex_handle>>& waiting_locks
) {
std::map<mutex_handle, std::set<mutex_handle>> graph;
for(auto& elem : waiting_locks) {
if(elem.second.has_value()) {
for(auto& n : owned_locks[elem.first]) {
graph[n].insert(elem.second.value());
}
}
}
std::set<mutex_handle> nodes;
{
lock_guard lister(lister_lock);
nodes = locks_that_exist;
}
bool happened = true;
while(happened) {
happened = false;
for(auto& n : nodes) {
if(graph[n].size() == 0)
{
happened = true;
for(auto v : graph) {
v.second.erase(n);
}
nodes.erase(n);
break;
}
}
}
return nodes.size();
}
void signal_locking(thread_state state, mutex_handle mtx, int64_t thrd) {
bool bad = false;
{
lock_guard checker(checker_lock);
switch(state) {
case thread_state::locking: {
waiting_locks[thrd].reset();
owned_locks[thrd].push_back(mtx);
} break;
case thread_state::unlocking: {
auto it = std::find(owned_locks[thrd].begin(), owned_locks[thrd].end(), mtx);
if(it != owned_locks[thrd].end()) {
owned_locks[thrd].erase(it);
}
} break;
case thread_state::waiting: {
waiting_locks[thrd] = mtx;
bad = build_dependency_graph(mtx, thrd, owned_locks, waiting_locks);
} break;
}
}
if(bad) throw std::runtime_error("Deadlock detected");
}
std::atomic<size_t> fast_bottleneck::counter;
/********************* ***********************/
fast_bottleneck A;
fast_bottleneck B;
int main() {
char c;
system::sys.current = std::make_unique<process>(&c);
std::cout << "1" << std::endl;
A.lock();
system::sys.current->state = process_status::running;
system::sys.yield_to(std::make_unique<process>([](){
A.lock();
std::cout << "A" << std::endl;
A.unlock();
}));
A.unlock();
system::sys.yield();
system::sys.yield_to(std::make_unique<process>([](){
A.lock();
std::cout << "B" << std::endl;
A.unlock();
}));
std::cout << "3" << std::endl;
return 0;
}