use signal safe synchronization with platform specific semaphores (#607)

* use signal safe synchronization with platform specific semaphores

Signed-off-by: William Woodall <william@osrfoundation.org>

* addressed feedback and refactored into separate files

Signed-off-by: William Woodall <william@osrfoundation.org>

* Apply suggestions from code review

Co-Authored-By: wjwwood <william+github@osrfoundation.org>

* include what you use (cpplint)

Signed-off-by: William Woodall <william@osrfoundation.org>

* avoid redundant use of SignalHandler::

Signed-off-by: William Woodall <william@osrfoundation.org>

* Update rclcpp/src/rclcpp/signal_handler.hpp

Co-Authored-By: wjwwood <william+github@osrfoundation.org>

* fix Windows build

Signed-off-by: William Woodall <william@osrfoundation.org>

* actually fix Windows

Signed-off-by: William Woodall <william@osrfoundation.org>

rclcpp/CMakeLists.txt

@@ -65,6 +65,7 @@ set(${PROJECT_NAME}_SRCS
   src/rclcpp/parameter_service.cpp
   src/rclcpp/publisher.cpp
   src/rclcpp/service.cpp
+  src/rclcpp/signal_handler.cpp
   src/rclcpp/subscription.cpp
   src/rclcpp/time.cpp
   src/rclcpp/time_source.cpp

rclcpp/src/rclcpp/signal_handler.cpp

@@ -0,0 +1,357 @@
+// Copyright 2018 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "./signal_handler.hpp"
+
+#include <atomic>
+#include <csignal>
+#include <mutex>
+#include <string>
+#include <thread>
+
+// includes for semaphore notification code
+#if defined(_WIN32)
+#include <windows.h>
+#elif defined(__APPLE__)
+#include <dispatch/dispatch.h>
+#else  // posix
+#include <semaphore.h>
+#endif
+
+#include "rclcpp/logging.hpp"
+#include "rmw/impl/cpp/demangle.hpp"
+
+using rclcpp::SignalHandler;
+
+// initialize static storage in SignalHandler class
+SignalHandler::signal_handler_type SignalHandler::old_signal_handler_;
+std::atomic_bool SignalHandler::signal_received_ = ATOMIC_VAR_INIT(false);
+std::atomic_bool SignalHandler::wait_for_signal_is_setup_ = ATOMIC_VAR_INIT(false);
+#if defined(_WIN32)
+HANDLE SignalHandler::signal_handler_sem_;
+#elif defined(__APPLE__)
+dispatch_semaphore_t SignalHandler::signal_handler_sem_;
+#else  // posix
+sem_t SignalHandler::signal_handler_sem_;
+#endif
+
+SignalHandler &
+SignalHandler::get_global_signal_handler()
+{
+  static SignalHandler signal_handler;
+  return signal_handler;
+}
+
+rclcpp::Logger &
+SignalHandler::get_logger()
+{
+  static rclcpp::Logger logger = rclcpp::get_logger("rclcpp");
+  return logger;
+}
+
+bool
+SignalHandler::install()
+{
+  std::lock_guard<std::mutex> lock(install_mutex_);
+  bool already_installed = installed_.exchange(true);
+  if (already_installed) {
+    return false;
+  }
+  try {
+    setup_wait_for_signal();
+    signal_received_.store(false);
+
+    SignalHandler::signal_handler_type signal_handler_argument;
+#if defined(RCLCPP_HAS_SIGACTION)
+    memset(&signal_handler_argument, 0, sizeof(signal_handler_argument));
+    sigemptyset(&signal_handler_argument.sa_mask);
+    signal_handler_argument.sa_sigaction = signal_handler;
+    signal_handler_argument.sa_flags = SA_SIGINFO;
+#else
+    signal_handler_argument = signal_handler;
+#endif
+
+    old_signal_handler_ = SignalHandler::set_signal_handler(SIGINT, signal_handler_argument);
+
+    signal_handler_thread_ = std::thread(&SignalHandler::deferred_signal_handler, this);
+  } catch (...) {
+    installed_.store(false);
+    throw;
+  }
+  RCLCPP_DEBUG(get_logger(), "signal handler installed");
+  return true;
+}
+
+bool
+SignalHandler::uninstall()
+{
+  std::lock_guard<std::mutex> lock(install_mutex_);
+  bool installed = installed_.exchange(false);
+  if (!installed) {
+    return false;
+  }
+  try {
+    // TODO(wjwwood): what happens if someone overrides our signal handler then calls uninstall?
+    //   I think we need to assert that we're the current signal handler, and mitigate if not.
+    set_signal_handler(SIGINT, old_signal_handler_);
+    RCLCPP_DEBUG(get_logger(), "SignalHandler::uninstall(): notifying deferred signal handler");
+    notify_signal_handler();
+    signal_handler_thread_.join();
+    teardown_wait_for_signal();
+  } catch (...) {
+    installed_.exchange(true);
+    throw;
+  }
+  RCLCPP_DEBUG(get_logger(), "signal handler uninstalled");
+  return true;
+}
+
+bool
+SignalHandler::is_installed()
+{
+  return installed_.load();
+}
+
+SignalHandler::~SignalHandler()
+{
+  try {
+    uninstall();
+  } catch (const std::exception & exc) {
+    RCLCPP_ERROR(
+      get_logger(),
+      "caught %s exception when uninstalling the sigint handler in rclcpp::~SignalHandler: %s",
+      rmw::impl::cpp::demangle(exc).c_str(), exc.what());
+  } catch (...) {
+    RCLCPP_ERROR(
+      get_logger(),
+      "caught unknown exception when uninstalling the sigint handler in rclcpp::~SignalHandler");
+  }
+}
+
+RCLCPP_LOCAL
+void
+__safe_strerror(int errnum, char * buffer, size_t buffer_length)
+{
+#if defined(_WIN32)
+  strerror_s(buffer, buffer_length, errnum);
+#elif (defined(_GNU_SOURCE) && !defined(ANDROID))
+  char * msg = strerror_r(errnum, buffer, buffer_length);
+  if (msg != buffer) {
+    strncpy(buffer, msg, buffer_length);
+    buffer[buffer_length - 1] = '\0';
+  }
+#else
+  int error_status = strerror_r(errnum, buffer, buffer_length);
+  if (error_status != 0) {
+    throw std::runtime_error("Failed to get error string for errno: " + std::to_string(errnum));
+  }
+#endif
+}
+
+SignalHandler::signal_handler_type
+SignalHandler::set_signal_handler(
+  int signal_value,
+  const SignalHandler::signal_handler_type & signal_handler)
+{
+  bool signal_handler_install_failed;
+  SignalHandler::signal_handler_type old_signal_handler;
+#if defined(RCLCPP_HAS_SIGACTION)
+  ssize_t ret = sigaction(signal_value, &signal_handler, &old_signal_handler);
+  signal_handler_install_failed = (ret == -1);
+#else
+  old_signal_handler = std::signal(signal_value, signal_handler);
+  signal_handler_install_failed = (old_signal_handler == SIG_ERR);
+#endif
+  if (signal_handler_install_failed) {
+    char error_string[1024];
+    __safe_strerror(errno, error_string, sizeof(error_string));
+    auto msg =
+      "Failed to set SIGINT signal handler (" + std::to_string(errno) + "): " + error_string;
+    throw std::runtime_error(msg);
+  }
+
+  return old_signal_handler;
+}
+
+void
+SignalHandler::signal_handler_common()
+{
+  signal_received_.store(true);
+  RCLCPP_DEBUG(
+    get_logger(),
+    "signal_handler(): SIGINT received, notifying deferred signal handler");
+  notify_signal_handler();
+}
+
+#if defined(RCLCPP_HAS_SIGACTION)
+void
+SignalHandler::signal_handler(int signal_value, siginfo_t * siginfo, void * context)
+{
+  RCLCPP_INFO(get_logger(), "signal_handler(signal_value=%d)", signal_value);
+
+  if (old_signal_handler_.sa_flags & SA_SIGINFO) {
+    if (old_signal_handler_.sa_sigaction != NULL) {
+      old_signal_handler_.sa_sigaction(signal_value, siginfo, context);
+    }
+  } else {
+    if (
+      old_signal_handler_.sa_handler != NULL &&  // Is set
+      old_signal_handler_.sa_handler != SIG_DFL &&  // Is not default
+      old_signal_handler_.sa_handler != SIG_IGN)  // Is not ignored
+    {
+      old_signal_handler_.sa_handler(signal_value);
+    }
+  }
+
+  signal_handler_common();
+}
+#else
+void
+SignalHandler::signal_handler(int signal_value)
+{
+  RCLCPP_INFO(get_logger(), "signal_handler(signal_value=%d)", signal_value);
+
+  if (old_signal_handler_) {
+    old_signal_handler_(signal_value);
+  }
+
+  signal_handler_common();
+}
+#endif
+
+void
+SignalHandler::deferred_signal_handler()
+{
+  while (true) {
+    if (signal_received_.exchange(false)) {
+      RCLCPP_DEBUG(get_logger(), "deferred_signal_handler(): SIGINT received, shutting down");
+      for (auto context_ptr : rclcpp::get_contexts()) {
+        if (context_ptr->get_init_options().shutdown_on_sigint) {
+          RCLCPP_DEBUG(
+            get_logger(),
+            "deferred_signal_handler(): "
+            "shutting down rclcpp::Context @ %p, because it had shutdown_on_sigint == true",
+            context_ptr.get());
+          context_ptr->shutdown("signal handler");
+        }
+      }
+    }
+    if (!is_installed()) {
+      RCLCPP_DEBUG(get_logger(), "deferred_signal_handler(): signal handling uninstalled");
+      break;
+    }
+    RCLCPP_DEBUG(get_logger(), "deferred_signal_handler(): waiting for SIGINT or uninstall");
+    wait_for_signal();
+    RCLCPP_DEBUG(get_logger(), "deferred_signal_handler(): woken up due to SIGINT or uninstall");
+  }
+}
+
+void
+SignalHandler::setup_wait_for_signal()
+{
+#if defined(_WIN32)
+  signal_handler_sem_ = CreateSemaphore(
+    NULL,  // default security attributes
+    0,  // initial semaphore count
+    1,  // maximum semaphore count
+    NULL);  // unnamed semaphore
+  if (NULL == signal_handler_sem_) {
+    throw std::runtime_error("CreateSemaphore() failed in setup_wait_for_signal()");
+  }
+#elif defined(__APPLE__)
+  signal_handler_sem_ = dispatch_semaphore_create(0);
+#else  // posix
+  if (-1 == sem_init(&signal_handler_sem_, 0, 0)) {
+    throw std::runtime_error(std::string("sem_init() failed: ") + strerror(errno));
+  }
+#endif
+  wait_for_signal_is_setup_.store(true);
+}
+
+void
+SignalHandler::teardown_wait_for_signal() noexcept
+{
+  if (!wait_for_signal_is_setup_.exchange(false)) {
+    return;
+  }
+#if defined(_WIN32)
+  CloseHandle(signal_handler_sem_);
+#elif defined(__APPLE__)
+  dispatch_release(signal_handler_sem_);
+#else  // posix
+  if (-1 == sem_destroy(&signal_handler_sem_)) {
+    RCLCPP_ERROR(get_logger(), "invalid semaphore in teardown_wait_for_signal()");
+  }
+#endif
+}
+
+void
+SignalHandler::wait_for_signal()
+{
+  if (!wait_for_signal_is_setup_.load()) {
+    RCLCPP_ERROR(get_logger(), "called wait_for_signal() before setup_wait_for_signal()");
+    return;
+  }
+#if defined(_WIN32)
+  DWORD dw_wait_result = WaitForSingleObject(signal_handler_sem_, INFINITE);
+  switch (dw_wait_result) {
+    case WAIT_ABANDONED:
+      RCLCPP_ERROR(
+        get_logger(), "WaitForSingleObject() failed in wait_for_signal() with WAIT_ABANDONED: %s",
+        GetLastError());
+      break;
+    case WAIT_OBJECT_0:
+      // successful
+      break;
+    case WAIT_TIMEOUT:
+      RCLCPP_ERROR(get_logger(), "WaitForSingleObject() timedout out in wait_for_signal()");
+      break;
+    case WAIT_FAILED:
+      RCLCPP_ERROR(
+        get_logger(), "WaitForSingleObject() failed in wait_for_signal(): %s", GetLastError());
+      break;
+    default:
+      RCLCPP_ERROR(
+        get_logger(), "WaitForSingleObject() gave unknown return in wait_for_signal(): %s",
+        GetLastError());
+  }
+#elif defined(__APPLE__)
+  dispatch_semaphore_wait(signal_handler_sem_, DISPATCH_TIME_FOREVER);
+#else  // posix
+  int s;
+  do {
+    s = sem_wait(&signal_handler_sem_);
+  } while (-1 == s && EINTR == errno);
+#endif
+}
+
+void
+SignalHandler::notify_signal_handler() noexcept
+{
+  if (!wait_for_signal_is_setup_.load()) {
+    return;
+  }
+#if defined(_WIN32)
+  if (!ReleaseSemaphore(signal_handler_sem_, 1, NULL)) {
+    RCLCPP_ERROR(
+      get_logger(), "ReleaseSemaphore() failed in notify_signal_handler(): %s", GetLastError());
+  }
+#elif defined(__APPLE__)
+  dispatch_semaphore_signal(signal_handler_sem_);
+#else  // posix
+  if (-1 == sem_post(&signal_handler_sem_)) {
+    RCLCPP_ERROR(get_logger(), "sem_post failed in notify_signal_handler()");
+  }
+#endif
+}