FEX-Emu--FEX/Source/Tools/LinuxEmulation/LinuxSyscalls/ThreadManager.cpp

// SPDX-License-Identifier: MIT

#include "LinuxSyscalls/Syscalls.h"
#include "LinuxSyscalls/SignalDelegator.h"

#include <FEXHeaderUtils/Syscalls.h>
#include <FEXCore/Utils/Profiler.h>
#include <FEXCore/fextl/fmt.h>

#include <sys/mman.h>
#include <sys/personality.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <git_version.h>

namespace FEX::HLE {

ThreadManager::StatAlloc::StatAlloc() {
  Initialize();
  SaveHeader(Is64BitMode() ? FEXCore::Profiler::AppType::LINUX_64 : FEXCore::Profiler::AppType::LINUX_32);
}

void ThreadManager::StatAlloc::Initialize() {
  if (!ProfileStats()) {
    return;
  }

  int fd = shm_open(fextl::fmt::format("fex-{}-stats", ::getpid()).c_str(), O_CREAT | O_TRUNC | O_RDWR, USER_PERMS);
  if (fd == -1) {
    return;
  }
  CurrentSize = sysconf(_SC_PAGESIZE);
  CurrentSize = CurrentSize > 0 ? CurrentSize : FEXCore::Utils::FEX_PAGE_SIZE;

  if (ftruncate(fd, CurrentSize) == -1) {
    LogMan::Msg::EFmt("[StatAlloc] ftruncate failed");
    goto err;
  }

  // Reserve a region of MAX_STATS_SIZE so we can grow the allocation buffer.
  // Number of thread slots when ThreadStatsHeader == 64bytes and ThreadStats == 40bytes:
  // 1 page: 99 slots
  // 1 MB: 26211 slots
  // 128 MB: 3355440 slots
  Base = ::mmap(nullptr, MAX_STATS_SIZE, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
  if (Base == MAP_FAILED) {
    LogMan::Msg::EFmt("[StatAlloc] mmap base failed");
    Base = nullptr;
    goto err;
  }

  // Allocate a small working shared space for now, grow as necessary.
  {
    auto SharedBase = ::mmap(Base, CurrentSize, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, 0);
    if (SharedBase == MAP_FAILED) {
      LogMan::Msg::EFmt("[StatAlloc] mmap shm failed");
      munmap(Base, MAX_STATS_SIZE);
      Base = nullptr;
      goto err;
    }
  }

err:
  close(fd);
}

uint32_t ThreadManager::StatAlloc::FrontendAllocateSlots(uint32_t NewSize) {
  if (CurrentSize == MAX_STATS_SIZE) {
    // Allocator has reached maximum slots. We can't allocate anymore.
    // New threads won't get stats.
    return CurrentSize;
  }
  NewSize = std::max(MAX_STATS_SIZE, NewSize);

  // When allocating more slots, open the fd without O_TRUNC | O_CREAT.
  int fd = shm_open(fextl::fmt::format("fex-{}-stats", ::getpid()).c_str(), O_RDWR, USER_PERMS);
  if (fd == -1) {
    return CurrentSize;
  }

  if (ftruncate(fd, NewSize) == -1) {
    LogMan::Msg::EFmt("[StatAlloc] ftruncate more failed");

    goto err;
  }

  {
    auto SharedBase = ::mmap(Base, NewSize, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, 0);
    if (SharedBase == MAP_FAILED) {
      LogMan::Msg::EFmt("[StatAlloc] allocate more mmap shm failed");
      goto err;
    }
  }

err:
  close(fd);
  return NewSize;
}

FEXCore::Profiler::ThreadStats* ThreadManager::StatAlloc::AllocateSlot(uint32_t TID) {
  std::scoped_lock lk(StatMutex);
  return StatAllocBase::AllocateSlot(TID);
}

void ThreadManager::StatAlloc::DeallocateSlot(FEXCore::Profiler::ThreadStats* AllocatedSlot) {
  if (!AllocatedSlot) {
    return;
  }

  std::scoped_lock lk(StatMutex);
  StatAllocBase::DeallocateSlot(AllocatedSlot);
}

void ThreadManager::StatAlloc::CleanupForExit() {
  shm_unlink(fextl::fmt::format("fex-{}-stats", ::getpid()).c_str());
}

void ThreadManager::StatAlloc::LockBeforeFork() {
  if (!ProfileStats()) {
    return;
  }
  StatMutex.lock();
}

void ThreadManager::StatAlloc::UnlockAfterFork(FEXCore::Core::InternalThreadState* Thread, bool Child) {
  if (!ProfileStats()) {
    return;
  }

  if (!Child) {
    StatMutex.unlock();
    return;
  }

  StatMutex.StealAndDropActiveLocks();

  // shm_memory ownership is retained by the parent process, so the child must replace it with its own one.
  // Otherwise this process will keep reporting in the original parent thread's stats region.
  munmap(Base, MAX_STATS_SIZE);
  Base = nullptr;
  CurrentSize = 0;
  Head = nullptr;
  Stats = nullptr;
  StatTail = nullptr;
  RemainingSlots = 0;

  Thread->ThreadStats = nullptr;

  Initialize();
  SaveHeader(Is64BitMode() ? FEXCore::Profiler::AppType::LINUX_64 : FEXCore::Profiler::AppType::LINUX_32);

  // Update this thread's ThreadStats object
  auto ThreadObject = FEX::HLE::ThreadManager::GetStateObjectFromFEXCoreThread(Thread);
  ThreadObject->Thread->ThreadStats = AllocateSlot(ThreadObject->ThreadInfo.TID);
}

FEX::HLE::ThreadStateObject* ThreadManager::CreateThread(uint64_t InitialRIP, uint64_t StackPointer, const FEXCore::Core::CPUState* NewThreadState,
                                                         uint64_t ParentTID, FEX::HLE::ThreadStateObject* InheritThread) {
  auto ThreadStateObject = new FEX::HLE::ThreadStateObject;

  ThreadStateObject->ThreadInfo.parent_tid = ParentTID;
  ThreadStateObject->ThreadInfo.PID = ::getpid();

  ThreadStateObject->ThreadInfo.TID = FHU::Syscalls::gettid();

  ThreadStateObject->Thread = CTX->CreateThread(InitialRIP, StackPointer, NewThreadState);
  ThreadStateObject->Thread->FrontendPtr = ThreadStateObject;
  if (ProfileStats()) {
    ThreadStateObject->Thread->ThreadStats = Stat.AllocateSlot(ThreadStateObject->ThreadInfo.TID);
  }

  if (InheritThread) {
    FEX::HLE::_SyscallHandler->SeccompEmulator.InheritSeccompFilters(InheritThread, ThreadStateObject);
    ThreadStateObject->persona = InheritThread->persona;
  } else {
    ThreadStateObject->persona = ::personality(0xffffffff);
  }

  ++IdleWaitRefCount;
  return ThreadStateObject;
}

void ThreadManager::DestroyThread(FEX::HLE::ThreadStateObject* Thread, bool NeedsTLSUninstall) {
  {
    std::lock_guard lk(ThreadCreationMutex);
    auto It = std::find(Threads.begin(), Threads.end(), Thread);
    LOGMAN_THROW_A_FMT(It != Threads.end(), "Thread wasn't in Threads");
    Threads.erase(It);
  }

  Stat.DeallocateSlot(Thread->Thread->ThreadStats);

  HandleThreadDeletion(Thread, NeedsTLSUninstall);
}

void ThreadManager::StopThread(FEX::HLE::ThreadStateObject* Thread) {
  SignalDelegation->SignalThread(Thread->Thread, SignalEvent::Stop);
}

void ThreadManager::HandleThreadDeletion(FEX::HLE::ThreadStateObject* Thread, bool NeedsTLSUninstall) {
  if (Thread->ExecutionThread) {
    if (Thread->ExecutionThread->joinable()) {
      Thread->ExecutionThread->join(nullptr);
    }

    if (Thread->ExecutionThread->IsSelf()) {
      Thread->ExecutionThread->detach();
    }
  }

  if (NeedsTLSUninstall) {
#if defined(ASSERTIONS_ENABLED) && ASSERTIONS_ENABLED
    // Sanity check. This can only be called from the owning thread.
    {
      const auto pid = ::getpid();
      const auto tid = FHU::Syscalls::gettid();
      LOGMAN_THROW_A_FMT(Thread->ThreadInfo.PID == pid && Thread->ThreadInfo.TID == tid, "Can't delete TLS data from a different thread!");
    }
#endif
    FEXCore::Allocator::UninstallTLSData(Thread->Thread);
  }

  CTX->DestroyThread(Thread->Thread);
  FEX::HLE::_SyscallHandler->SeccompEmulator.FreeSeccompFilters(Thread);

  delete Thread;
  --IdleWaitRefCount;
  IdleWaitCV.notify_all();
}

void ThreadManager::NotifyPause() {
  // Tell all the threads that they should pause
  std::lock_guard lk(ThreadCreationMutex);
  for (auto& Thread : Threads) {
    SignalDelegation->SignalThread(Thread->Thread, SignalEvent::Pause);
  }
}

void ThreadManager::Pause() {
#if defined(ASSERTIONS_ENABLED) && ASSERTIONS_ENABLED
  // Sanity check. This can't be called from an emulation thread.
  {
    const auto pid = ::getpid();
    const auto tid = FHU::Syscalls::gettid();
    std::lock_guard lk(ThreadCreationMutex);
    for (auto& Thread : Threads) {
      LOGMAN_THROW_A_FMT(!(Thread->ThreadInfo.PID == pid && Thread->ThreadInfo.TID == tid), "Can't put threads to sleep from inside "
                                                                                            "emulation thread!");
    }
  }
#endif
  NotifyPause();
  WaitForIdle();
}

void ThreadManager::Run() {
  // Spin up all the threads
  std::lock_guard lk(ThreadCreationMutex);
  for (auto& Thread : Threads) {
    Thread->SignalReason.store(SignalEvent::Return);
  }
}

void ThreadManager::WaitForIdleWithTimeout() {
  std::unique_lock<std::mutex> lk(IdleWaitMutex);
  bool WaitResult = IdleWaitCV.wait_for(lk, std::chrono::milliseconds(1500), [this] { return IdleWaitRefCount.load() == 0; });

  if (!WaitResult) {
    // The wait failed, this will occur if we stepped in to a syscall
    // That's okay, we just need to pause the threads manually
    NotifyPause();
  }

  // We have sent every thread a pause signal
  // Now wait again because they /will/ be going to sleep
  WaitForIdle();
}

void ThreadManager::WaitForThreadsToRun() {
  size_t NumThreads {};
  {
    std::lock_guard lk(ThreadCreationMutex);
    NumThreads = Threads.size();
  }

  // Spin while waiting for the threads to start up
  std::unique_lock<std::mutex> lk(IdleWaitMutex);
  IdleWaitCV.wait(lk, [this, NumThreads] { return IdleWaitRefCount.load() >= NumThreads; });

  Running = true;
}

void ThreadManager::Step() {
  LogMan::Msg::AFmt("ThreadManager::Step currently not implemented");
  {
    std::lock_guard lk(ThreadCreationMutex);
    // Walk the threads and tell them to clear their caches
    // Useful when our block size is set to a large number and we need to step a single instruction
    for (auto& Thread : Threads) {
      CTX->ClearCodeCache(Thread->Thread);
    }
  }

  // TODO: Set to single step mode.
  Run();
  WaitForThreadsToRun();
  WaitForIdle();
  // TODO: Set back to full running mode.
}

void ThreadManager::Stop(bool IgnoreCurrentThread) {
  pid_t tid = FHU::Syscalls::gettid();
  FEX::HLE::ThreadStateObject* CurrentThread {};

  // Tell all the threads that they should stop
  {
    std::lock_guard lk(ThreadCreationMutex);
    for (auto& Thread : Threads) {
      if (IgnoreCurrentThread && Thread->ThreadInfo.TID == tid) {
        // If we are callign stop from the current thread then we can ignore sending signals to this thread
        // This means that this thread is already gone
      } else if (Thread->ThreadInfo.TID == tid) {
        // We need to save the current thread for last to ensure all threads receive their stop signals
        CurrentThread = Thread;
        continue;
      }

      StopThread(Thread);
    }
  }

  // Stop the current thread now if we aren't ignoring it
  if (CurrentThread) {
    StopThread(CurrentThread);
  }
}

void ThreadManager::SleepThread(FEXCore::Context::Context* CTX, FEXCore::Core::CpuStateFrame* Frame) {
  auto ThreadObject = FEX::HLE::ThreadManager::GetStateObjectFromCPUState(Frame);
#if defined(ASSERTIONS_ENABLED) && ASSERTIONS_ENABLED
  // Sanity check. This can only be called from the owning thread.
  {
    const auto pid = ::getpid();
    const auto tid = FHU::Syscalls::gettid();
    LOGMAN_THROW_A_FMT(ThreadObject->ThreadInfo.PID == pid && ThreadObject->ThreadInfo.TID == tid, "Can't delete TLS data from a different "
                                                                                                   "thread!");
  }
#endif

  --IdleWaitRefCount;
  IdleWaitCV.notify_all();

  ThreadObject->ThreadSleeping = true;

  // Go to sleep
  ThreadObject->ThreadPaused.Wait();

  ++IdleWaitRefCount;
  ThreadObject->ThreadSleeping = false;

  IdleWaitCV.notify_all();
}

void ThreadManager::UnpauseThread(FEX::HLE::ThreadStateObject* Thread) {
  Thread->ThreadPaused.NotifyOne();
}

void ThreadManager::LockBeforeFork() {
  Stat.LockBeforeFork();
}

void ThreadManager::UnlockAfterFork(FEXCore::Core::InternalThreadState* LiveThread, bool Child) {
  Stat.UnlockAfterFork(LiveThread, Child);
  if (!Child) {
    return;
  }

  // This function is called after fork
  // We need to cleanup some of the thread data that is dead
  for (auto& DeadThread : Threads) {
    // The fork parent retains ownership of ThreadStats
    DeadThread->Thread->ThreadStats = nullptr;

    if (DeadThread->Thread == LiveThread) {
      continue;
    }

    // Despite what google searches may susgest, glibc actually has special code to handle forks
    // with multiple active threads.
    // It cleans up the stacks of dead threads and marks them as terminated.
    // It also cleans up a bunch of internal mutexes.

    // FIXME: TLS is probally still alive. Investigate

    // Deconstructing the Interneal thread state should clean up most of the state.
    // But if anything on the now deleted stack is holding a refrence to the heap, it will be leaked
    CTX->DestroyThread(DeadThread->Thread);
    delete DeadThread;

    // FIXME: Make sure sure nothing gets leaked via the heap. Ideas:
    //         * Make sure nothing is allocated on the heap without ref in InternalThreadState
    //         * Surround any code that heap allocates with a per-thread mutex.
    //           Before forking, the the forking thread can lock all thread mutexes.
  }

  // Remove all threads but the live thread from Threads
  Threads.clear();

  auto ThreadObject = FEX::HLE::ThreadManager::GetStateObjectFromCPUState(LiveThread->CurrentFrame);
  Threads.push_back(ThreadObject);

  // Clean up dead stacks
  FEXCore::Threads::Thread::CleanupAfterFork();

  // We now only have one thread.
  IdleWaitRefCount = 1;
  ThreadCreationMutex.StealAndDropActiveLocks();
}

void ThreadManager::WaitForIdle() {
  std::unique_lock<std::mutex> lk(IdleWaitMutex);
  IdleWaitCV.wait(lk, [this] { return IdleWaitRefCount.load() == 0; });

  Running = false;
}

ThreadManager::~ThreadManager() {
  std::lock_guard lk(ThreadCreationMutex);

  for (auto& Thread : Threads) {
    HandleThreadDeletion(Thread);
  }
  Threads.clear();
}
} // namespace FEX::HLE