Update linux host to handle SIGHUP. use it to reload config.

remoting/host/sighup_listener_mac.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// TODO(jamiewalch): Add unit tests for this.
-
-#include "remoting/host/sighup_listener_mac.h"
-
-#include <errno.h>
-
-#include "base/compiler_specific.h"
-#include "base/eintr_wrapper.h"
-#include "base/message_loop.h"
-#include "base/message_pump_libevent.h"
-#include "base/threading/platform_thread.h"
-
-namespace {
-
-class SigHupListener : public base::MessagePumpLibevent::Watcher {
- public:
-  SigHupListener(const base::Closure& callback);
-
-  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
-  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE {}
-
-  // WatchFileDescriptor needs a controller through which the operation can be
-  // canceled. We don't use it, but this is as good a place as any to store it.
-  base::MessagePumpLibevent::FileDescriptorWatcher controller;
-
- private:
-  base::Closure callback_;
-};
-
-SigHupListener::SigHupListener(const base::Closure& callback)
-    : callback_(callback) {
-}
-
-void SigHupListener::OnFileCanReadWithoutBlocking(int fd) {
-  char buffer;
-  int result = HANDLE_EINTR(read(fd, &buffer, sizeof(buffer)));
-  if (result > 0) {
-    callback_.Run();
-  }
-}
-
-SigHupListener* g_config_updater = NULL;
-int g_write_fd = 0;
-
-void HupSignalHandler(int signal) {
-  int r ALLOW_UNUSED = write(g_write_fd, "", 1);
-}
-
-}  // namespace
-
-namespace remoting {
-
-// RegisterHupSignalHandler registers a signal handler that writes a byte to a
-// pipe each time SIGHUP is received. The read end of the pipe is registered
-// with the current MessageLoop (which must be of type IO); whenever the pipe
-// is readable, it invokes the specified callback.
-//
-// This arrangement is required because the set of system APIs that are safe to
-// call from a singal handler is very limited (but does include write).
-bool RegisterHupSignalHandler(const base::Closure& callback) {
-  DCHECK(!g_config_updater);
-  MessageLoopForIO* message_loop = MessageLoopForIO::current();
-  int pipefd[2];
-  int result = pipe(pipefd);
-  if (result < 0) {
-    LOG(ERROR) << "Could not create SIGHUP pipe: " << errno;
-    return false;
-  }
-  g_write_fd = pipefd[1];
-  g_config_updater = new SigHupListener(callback);
-  result = message_loop->WatchFileDescriptor(
-      pipefd[0], true, MessageLoopForIO::WATCH_READ,
-      &g_config_updater->controller, g_config_updater);
-  if (!result) {
-    delete g_config_updater;
-    g_config_updater = NULL;
-    LOG(ERROR) << "Failed to create SIGHUP detector task.";
-    return false;
-  }
-  if (signal(SIGHUP, HupSignalHandler) == SIG_ERR) {
-    delete g_config_updater;
-    g_config_updater = NULL;
-    LOG(ERROR) << "signal() failed: " << errno;
-    return false;
-  }
-  return true;
-}
-
-}  // namespace remoting