Accelerator.cpp

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//===- Accelerator.cpp - ESI accelerator system API -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// DO NOT EDIT!
// This file is distributed as part of an ESI package. The source for this file
// should always be modified within CIRCT (lib/dialect/ESI/runtime/cpp/).
//
//===----------------------------------------------------------------------===//
 
#include "esi/Accelerator.h"
 
#include <cassert>
#include <cstdlib>
#include <filesystem>
#include <map>
#include <sstream>
#include <stdexcept>
#include <vector>
 
#include <iostream>
 
#ifdef __linux__
#include <dlfcn.h>
#include <linux/limits.h>
#include <unistd.h>
#elif _WIN32
#include <windows.h>
#endif
 
using namespace esi;
using namespace esi::services;
 
namespace esi {
AcceleratorConnection::AcceleratorConnection(Context &ctxt)
    : ctxt(ctxt), serviceThread(nullptr) {}
AcceleratorConnection::~AcceleratorConnection() { disconnect(); }
 
AcceleratorServiceThread *AcceleratorConnection::getServiceThread() {
  if (!serviceThread)
    serviceThread = std::make_unique<AcceleratorServiceThread>();
  return serviceThread.get();
}
void AcceleratorConnection::createEngine(const std::string &engineTypeName,
                                         AppIDPath idPath,
                                         const ServiceImplDetails &details,
                                         const HWClientDetails &clients) {
  std::unique_ptr<Engine> engine = ::esi::registry::createEngine(
      *this, engineTypeName, idPath, details, clients);
  registerEngine(idPath, std::move(engine), clients);
}
 
void AcceleratorConnection::registerEngine(AppIDPath idPath,
                                           std::unique_ptr<Engine> engine,
                                           const HWClientDetails &clients) {
  assert(engine);
  auto [engineIter, _] = ownedEngines.emplace(idPath, std::move(engine));
 
  // Engine is now owned by the accelerator connection, so the std::unique_ptr
  // is no longer valid. Resolve a new one from the map iter.
  Engine *enginePtr = engineIter->second.get();
  // Compute our parents idPath path.
  AppIDPath prefix = std::move(idPath);
  if (prefix.size() > 0)
    prefix.pop_back();
 
  for (const auto &client : clients) {
    AppIDPath fullClientPath = prefix + client.relPath;
    for (const auto &channel : client.channelAssignments)
      clientEngines[fullClientPath].setEngine(channel.first, enginePtr);
  }
}
 
services::Service *AcceleratorConnection::getService(Service::Type svcType,
                                                     AppIDPath id,
                                                     std::string implName,
                                                     ServiceImplDetails details,
                                                     HWClientDetails clients) {
  std::unique_ptr<Service> &cacheEntry =
      serviceCache[make_tuple(std::string(svcType.name()), id)];
  if (cacheEntry == nullptr) {
    Service *svc = createService(svcType, id, implName, details, clients);
    if (!svc)
      svc = ServiceRegistry::createService(this, svcType, id, implName, details,
                                           clients);
    if (!svc)
      return nullptr;
    cacheEntry = std::unique_ptr<Service>(svc);
  }
  return cacheEntry.get();
}
 
Accelerator *
AcceleratorConnection::takeOwnership(std::unique_ptr<Accelerator> acc) {
  if (ownedAccelerator)
    throw std::runtime_error(
        "AcceleratorConnection already owns an accelerator");
  ownedAccelerator = std::move(acc);
  return ownedAccelerator.get();
}
 
/// Get the path to the currently running executable.
static std::filesystem::path getExePath() {
#ifdef __linux__
  char result[PATH_MAX];
  ssize_t count = readlink("/proc/self/exe", result, PATH_MAX);
  if (count == -1)
    throw std::runtime_error("Could not get executable path");
  return std::filesystem::path(std::string(result, count));
#elif _WIN32
  char buffer[MAX_PATH];
  DWORD length = GetModuleFileNameA(NULL, buffer, MAX_PATH);
  if (length == 0)
    throw std::runtime_error("Could not get executable path");
  return std::filesystem::path(std::string(buffer, length));
#else
#eror "Unsupported platform"
#endif
}
 
/// Get the path to the currently running shared library.
static std::filesystem::path getLibPath() {
#ifdef __linux__
  Dl_info dl_info;
  dladdr((void *)getLibPath, &dl_info);
  return std::filesystem::path(std::string(dl_info.dli_fname));
#elif _WIN32
  HMODULE hModule = NULL;
  if (!GetModuleHandleExA(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
                              GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
                          reinterpret_cast<LPCSTR>(&getLibPath), &hModule)) {
    // Handle error
    return std::filesystem::path();
  }
 
  char buffer[MAX_PATH];
  DWORD length = GetModuleFileNameA(hModule, buffer, MAX_PATH);
  if (length == 0)
    throw std::runtime_error("Could not get library path");
 
  return std::filesystem::path(std::string(buffer, length));
#else
#eror "Unsupported platform"
#endif
}
 
/// Get the list of directories to search for backend plugins.
static std::vector<std::filesystem::path> getESIBackendDirectories() {
  std::vector<std::filesystem::path> directories;
 
  // First, check current directory.
  directories.push_back(std::filesystem::current_path());
 
  // Next, parse the ESI_BACKENDS environment variable and add those.
  const char *esiBackends = std::getenv("ESI_BACKENDS");
  if (esiBackends) {
    // Use platform-specific path separator
#ifdef _WIN32
    const char separator = ';';
#else
    const char separator = ':';
#endif
 
    std::string pathsStr(esiBackends);
    std::stringstream ss(pathsStr);
    std::string path;
 
    while (std::getline(ss, path, separator))
      if (!path.empty())
        directories.emplace_back(path);
  }
 
  // Next, try the directory of the executable.
  directories.push_back(getExePath().parent_path());
  // Finally, try the directory of the library.
  directories.push_back(getLibPath().parent_path());
 
  return directories;
}
 
/// Load a backend plugin dynamically. Plugins are expected to be named
/// lib<BackendName>Backend.so and located in one of 1) CWD, 2) directories
/// specified in ESI_BACKENDS environment variable, 3) in the same directory as
/// the application, or 4) in the same directory as this library.
static void loadBackend(Context &ctxt, std::string backend) {
  Logger &logger = ctxt.getLogger();
  backend[0] = toupper(backend[0]);
 
  // Get the file name we are looking for.
#ifdef __linux__
  std::string backendFileName = "lib" + backend + "Backend.so";
#elif _WIN32
  // In MSVC debug builds, load the debug variant of the plugin DLL (e.g.
  // CosimBackend_d.dll) to ensure compatibility.
#if defined(_MSC_VER) && defined(_DEBUG)
  std::string backendFileName = backend + "Backend_d.dll";
#else
  std::string backendFileName = backend + "Backend.dll";
#endif
#else
#error "Unsupported platform"
#endif
 
  // First, try the current directory.
  std::filesystem::path backendPath;
  // Next, try directories specified in ESI_BACKENDS environment variable.
  std::vector<std::filesystem::path> esiBackendDirs =
      getESIBackendDirectories();
  bool found = false;
  for (const auto &dir : esiBackendDirs) {
    backendPath = dir / backendFileName;
    logger.debug("CONNECT",
                 "trying to find backend plugin: " + backendPath.string());
    if (std::filesystem::exists(backendPath)) {
      found = true;
      break;
    }
  }
 
  // If the path was found, convert it to a string.
  if (found) {
    backendPath = std::filesystem::absolute(backendPath);
    logger.debug("CONNECT", "found backend plugin: " + backendPath.string());
  } else {
    // If all else fails, just try the name.
    backendPath = backendFileName;
    logger.debug("CONNECT",
                 "trying to find backend plugin: " + backendFileName);
  }
 
  // Attempt to load it.
#ifdef __linux__
  void *handle = dlopen(backendPath.string().c_str(), RTLD_NOW | RTLD_GLOBAL);
  if (!handle) {
    std::string error(dlerror());
    logger.error("CONNECT",
                 "while attempting to load backend plugin: " + error);
    throw std::runtime_error("While attempting to load backend plugin: " +
                             error);
  }
#elif _WIN32
  // Set the DLL directory to the same directory as the backend DLL in case it
  // has transitive dependencies.
  if (found) {
    std::filesystem::path backendPathParent = backendPath.parent_path();
    // If backendPath has no parent directory (e.g., it's a relative path or
    // a filename without a directory), fallback to the current working
    // directory. This ensures a valid directory is used for setting the DLL
    // search path.
    if (backendPathParent.empty())
      backendPathParent = std::filesystem::current_path();
    logger.debug("CONNECT", "setting DLL search directory to: " +
                                backendPathParent.string());
    if (SetDllDirectoryA(backendPathParent.string().c_str()) == 0)
      throw std::runtime_error("While setting DLL directory: " +
                               std::to_string(GetLastError()));
  }
 
  // Load the backend plugin.
  HMODULE handle = LoadLibraryA(backendPath.string().c_str());
  if (!handle) {
    DWORD error = GetLastError();
    // Get the error message string
    LPSTR messageBuffer = nullptr;
    size_t size = FormatMessageA(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
            FORMAT_MESSAGE_IGNORE_INSERTS,
        nullptr, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPSTR)&messageBuffer, 0, nullptr);
 
    std::string errorMessage;
    if (size > 0 && messageBuffer != nullptr) {
      errorMessage = std::string(messageBuffer, size);
      LocalFree(messageBuffer);
    } else {
      errorMessage = "Unknown error";
    }
 
    std::string fullError = "While attempting to load backend plugin '" +
                            backendPath.string() + "': " + errorMessage +
                            " (error code: " + std::to_string(error) + ")";
 
    logger.error("CONNECT", fullError);
    throw std::runtime_error(fullError);
  }
#else
#eror "Unsupported platform"
#endif
  logger.info("CONNECT", "loaded backend plugin: " + backendPath.string());
}
 
namespace registry {
namespace internal {
 
class BackendRegistry {
public:
  static std::map<std::string, BackendCreate> &get() {
    static BackendRegistry instance;
    return instance.backendRegistry;
  }
 
private:
  std::map<std::string, BackendCreate> backendRegistry;
};
 
void registerBackend(const std::string &name, BackendCreate create) {
  auto &registry = BackendRegistry::get();
  if (registry.count(name))
    throw std::runtime_error("Backend already exists in registry");
  registry[name] = create;
}
} // namespace internal
 
} // namespace registry
 
AcceleratorConnection *Context::connect(std::string backend,
                                        std::string connection) {
  auto &registry = registry::internal::BackendRegistry::get();
  auto f = registry.find(backend);
  if (f == registry.end()) {
    // If it's not already found in the registry, try to load it dynamically.
    loadBackend(*this, backend);
    f = registry.find(backend);
    if (f == registry.end()) {
      ServiceImplDetails details;
      details["backend"] = backend;
      std::ostringstream loaded_backends;
      bool first = true;
      for (const auto &b : registry) {
        if (!first)
          loaded_backends << ", ";
        loaded_backends << b.first;
        first = false;
      }
      details["loaded_backends"] = loaded_backends.str();
      getLogger().error("CONNECT", "backend '" + backend + "' not found",
                        &details);
      throw std::runtime_error("Backend '" + backend + "' not found");
    }
  }
  getLogger().info("CONNECT", "connecting to backend " + backend + " via '" +
                                  connection + "'");
  auto conn = f->second(*this, connection);
  auto *connPtr = conn.get();
  connections.emplace_back(std::move(conn));
  return connPtr;
}
 
struct AcceleratorServiceThread::Impl {
  Impl() {}
  void start() { me = std::thread(&Impl::loop, this); }
  void stop() {
    shutdown = true;
    me.join();
  }
  /// When there's data on any of the listenPorts, call the callback. This
  /// method can be called from any thread.
  void
  addListener(std::initializer_list<ReadChannelPort *> listenPorts,
              std::function<void(ReadChannelPort *, MessageData)> callback);
 
  void addTask(std::function<void(void)> task) {
    std::lock_guard<std::mutex> g(m);
    taskList.push_back(task);
  }
 
private:
  void loop();
  volatile bool shutdown = false;
  std::thread me;
 
  // Protect the shared data structures.
  std::mutex m;
 
  // Map of read ports to callbacks.
  std::map<ReadChannelPort *,
           std::pair<std::function<void(ReadChannelPort *, MessageData)>,
                     std::future<MessageData>>>
      listeners;
 
  /// Tasks which should be called on every loop iteration.
  std::vector<std::function<void(void)>> taskList;
};
 
void AcceleratorServiceThread::Impl::loop() {
  // These two variables should logically be in the loop, but this avoids
  // reconstructing them on each iteration.
  std::vector<std::tuple<ReadChannelPort *,
                         std::function<void(ReadChannelPort *, MessageData)>,
                         MessageData>>
      portUnlockWorkList;
  std::vector<std::function<void(void)>> taskListCopy;
  MessageData data;
 
  while (!shutdown) {
    // Ideally we'd have some wake notification here, but this sufficies for
    // now.
    // TODO: investigate better ways to do this. For now, just play nice with
    // the other processes but don't waste time in between polling intervals.
    std::this_thread::yield();
 
    // Check and gather data from all the read ports we are monitoring. Put the
    // callbacks to be called later so we can release the lock.
    {
      std::lock_guard<std::mutex> g(m);
      for (auto &[channel, cbfPair] : listeners) {
        assert(channel && "Null channel in listener list");
        std::future<MessageData> &f = cbfPair.second;
        if (f.wait_for(std::chrono::seconds(0)) == std::future_status::ready) {
          portUnlockWorkList.emplace_back(channel, cbfPair.first, f.get());
          f = channel->readAsync();
        }
      }
    }
 
    // Call the callbacks outside the lock.
    for (auto [channel, cb, data] : portUnlockWorkList)
      cb(channel, std::move(data));
 
    // Clear the worklist for the next iteration.
    portUnlockWorkList.clear();
 
    // Call any tasks that have been added. Copy it first so we can release the
    // lock ASAP.
    {
      std::lock_guard<std::mutex> g(m);
      taskListCopy = taskList;
    }
    for (auto &task : taskListCopy)
      task();
  }
}
 
void AcceleratorServiceThread::Impl::addListener(
    std::initializer_list<ReadChannelPort *> listenPorts,
    std::function<void(ReadChannelPort *, MessageData)> callback) {
  std::lock_guard<std::mutex> g(m);
  for (auto port : listenPorts) {
    if (listeners.count(port))
      throw std::runtime_error("Port already has a listener");
    listeners[port] = std::make_pair(callback, port->readAsync());
  }
}
 
AcceleratorServiceThread::AcceleratorServiceThread()
    : impl(std::make_unique<Impl>()) {
  impl->start();
}
AcceleratorServiceThread::~AcceleratorServiceThread() { stop(); }
 
void AcceleratorServiceThread::stop() {
  if (impl) {
    impl->stop();
    impl.reset();
  }
}
 
// When there's data on any of the listenPorts, call the callback. This is
// kinda silly now that we have callback port support, especially given the
// polling loop. Keep the functionality for now.
void AcceleratorServiceThread::addListener(
    std::initializer_list<ReadChannelPort *> listenPorts,
    std::function<void(ReadChannelPort *, MessageData)> callback) {
  assert(impl && "Service thread not running");
  impl->addListener(listenPorts, callback);
}
 
void AcceleratorServiceThread::addPoll(HWModule &module) {
  assert(impl && "Service thread not running");
  impl->addTask([&module]() { module.poll(); });
}
 
void AcceleratorConnection::disconnect() {
  if (serviceThread) {
    serviceThread->stop();
    serviceThread.reset();
  }
}
 
} // namespace esi