chrome/browser/browser_main_posix.cc

// Copyright (c) 2010 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.

#include <errno.h>
#include <signal.h>
#include <sys/resource.h>

#include "base/command_line.h"
#include "base/eintr_wrapper.h"
#include "base/logging.h"
#include "base/string_util.h"
#include "chrome/browser/browser_list.h"
#include "chrome/browser/browser_main.h"
#include "chrome/browser/chrome_thread.h"
#include "chrome/common/chrome_switches.h"

namespace {

// See comment in |PreEarlyInitialization()|, where sigaction is called.
void SIGCHLDHandler(int signal) {
}

int g_shutdown_pipe_write_fd = -1;
int g_shutdown_pipe_read_fd = -1;

// Common code between SIG{HUP, INT, TERM}Handler.
void GracefulShutdownHandler(int signal) {
  // Reinstall the default handler.  We had one shot at graceful shutdown.
  struct sigaction action;
  memset(&action, 0, sizeof(action));
  action.sa_handler = SIG_DFL;
  RAW_CHECK(sigaction(signal, &action, NULL) == 0);

  RAW_CHECK(g_shutdown_pipe_write_fd != -1);
  RAW_CHECK(g_shutdown_pipe_read_fd != -1);
  size_t bytes_written = 0;
  do {
    int rv = HANDLE_EINTR(
        write(g_shutdown_pipe_write_fd,
              reinterpret_cast<const char*>(&signal) + bytes_written,
              sizeof(signal) - bytes_written));
    RAW_CHECK(rv >= 0);
    bytes_written += rv;
  } while (bytes_written < sizeof(signal));

  RAW_LOG(INFO,
          "Successfully wrote to shutdown pipe, resetting signal handler.");
}

// See comment in |PreEarlyInitialization()|, where sigaction is called.
void SIGHUPHandler(int signal) {
  RAW_CHECK(signal == SIGHUP);
  RAW_LOG(INFO, "Handling SIGHUP.");
  GracefulShutdownHandler(signal);
}

// See comment in |PreEarlyInitialization()|, where sigaction is called.
void SIGINTHandler(int signal) {
  RAW_CHECK(signal == SIGINT);
  RAW_LOG(INFO, "Handling SIGINT.");
  GracefulShutdownHandler(signal);
}

// See comment in |PreEarlyInitialization()|, where sigaction is called.
void SIGTERMHandler(int signal) {
  RAW_CHECK(signal == SIGTERM);
  RAW_LOG(INFO, "Handling SIGTERM.");
  GracefulShutdownHandler(signal);
}

class ShutdownDetector : public PlatformThread::Delegate {
 public:
  explicit ShutdownDetector(int shutdown_fd);

  virtual void ThreadMain();

 private:
  const int shutdown_fd_;

  DISALLOW_COPY_AND_ASSIGN(ShutdownDetector);
};

ShutdownDetector::ShutdownDetector(int shutdown_fd)
    : shutdown_fd_(shutdown_fd) {
  CHECK_NE(shutdown_fd_, -1);
}

void ShutdownDetector::ThreadMain() {
  int signal;
  size_t bytes_read = 0;
  ssize_t ret;
  do {
    ret = HANDLE_EINTR(
        read(shutdown_fd_,
             reinterpret_cast<char*>(&signal) + bytes_read,
             sizeof(signal) - bytes_read));
    if (ret < 0) {
      NOTREACHED() << "Unexpected error: " << strerror(errno);
      break;
    } else if (ret == 0) {
      NOTREACHED() << "Unexpected closure of shutdown pipe.";
      break;
    }
    bytes_read += ret;
  } while (bytes_read < sizeof(signal));

  LOG(INFO) << "Handling shutdown for signal " << signal << ".";

  if (!ChromeThread::PostTask(
      ChromeThread::UI, FROM_HERE,
      NewRunnableFunction(BrowserList::CloseAllBrowsersAndExit))) {
    // Without a UI thread to post the exit task to, there aren't many
    // options.  Raise the signal again.  The default handler will pick it up
    // and cause an ungraceful exit.
    RAW_LOG(WARNING, "No UI thread, exiting ungracefully.");
    kill(getpid(), signal);

    // The signal may be handled on another thread.  Give that a chance to
    // happen.
    sleep(3);

    // We really should be dead by now.  For whatever reason, we're not. Exit
    // immediately, with the exit status set to the signal number with bit 8
    // set.  On the systems that we care about, this exit status is what is
    // normally used to indicate an exit by this signal's default handler.
    // This mechanism isn't a de jure standard, but even in the worst case, it
    // should at least result in an immediate exit.
    RAW_LOG(WARNING, "Still here, exiting really ungracefully.");
    _exit(signal | (1 << 7));
  }
}

// Sets the file descriptor soft limit to |max_descriptors| or the OS hard
// limit, whichever is lower.
void SetFileDescriptorLimit(unsigned int max_descriptors) {
  struct rlimit limits;
  if (getrlimit(RLIMIT_NOFILE, &limits) == 0) {
    unsigned int new_limit = max_descriptors;
    if (limits.rlim_max > 0 && limits.rlim_max < max_descriptors) {
      new_limit = limits.rlim_max;
    }
    limits.rlim_cur = new_limit;
    if (setrlimit(RLIMIT_NOFILE, &limits) != 0) {
      PLOG(INFO) << "Failed to set file descriptor limit";
    }
  } else {
    PLOG(INFO) << "Failed to get file descriptor limit";
  }
}

}  // namespace

// BrowserMainPartsPosix -------------------------------------------------------

class BrowserMainPartsPosix : public BrowserMainParts {
 public:
  explicit BrowserMainPartsPosix(const MainFunctionParams& parameters)
      : BrowserMainParts(parameters) {}

  virtual void TemporaryPosix_1() {
    int pipefd[2];
    int ret = pipe(pipefd);
    if (ret < 0) {
      PLOG(DFATAL) << "Failed to create pipe";
    } else {
      g_shutdown_pipe_read_fd = pipefd[0];
      g_shutdown_pipe_write_fd = pipefd[1];
      const size_t kShutdownDetectorThreadStackSize = 4096;
      if (!PlatformThread::CreateNonJoinable(
          kShutdownDetectorThreadStackSize,
          new ShutdownDetector(g_shutdown_pipe_read_fd))) {
        LOG(DFATAL) << "Failed to create shutdown detector task.";
      }
    }
  }

 private:
  virtual void PreEarlyInitialization() {
    // We need to accept SIGCHLD, even though our handler is a no-op because
    // otherwise we cannot wait on children. (According to POSIX 2001.)
    struct sigaction action;
    memset(&action, 0, sizeof(action));
    action.sa_handler = SIGCHLDHandler;
    CHECK(sigaction(SIGCHLD, &action, NULL) == 0);

    // If adding to this list of signal handlers, note the new signal probably
    // needs to be reset in child processes. See
    // base/process_util_posix.cc:LaunchApp

    // We need to handle SIGTERM, because that is how many POSIX-based distros
    // ask processes to quit gracefully at shutdown time.
    memset(&action, 0, sizeof(action));
    action.sa_handler = SIGTERMHandler;
    CHECK(sigaction(SIGTERM, &action, NULL) == 0);
    // Also handle SIGINT - when the user terminates the browser via Ctrl+C. If
    // the browser process is being debugged, GDB will catch the SIGINT first.
    action.sa_handler = SIGINTHandler;
    CHECK(sigaction(SIGINT, &action, NULL) == 0);
    // And SIGHUP, for when the terminal disappears. On shutdown, many Linux
    // distros send SIGHUP, SIGTERM, and then SIGKILL.
    action.sa_handler = SIGHUPHandler;
    CHECK(sigaction(SIGHUP, &action, NULL) == 0);

    const std::string fd_limit_string =
        parsed_command_line().GetSwitchValueASCII(
            switches::kFileDescriptorLimit);
    int fd_limit = 0;
    if (!fd_limit_string.empty()) {
      StringToInt(fd_limit_string, &fd_limit);
    }
#if defined(OS_MACOSX)
    // We use quite a few file descriptors for our IPC, and the default limit on
    // the Mac is low (256), so bump it up if there is no explicit override.
    if (fd_limit == 0) {
      fd_limit = 1024;
    }
#endif  // OS_MACOSX
    if (fd_limit > 0)
      SetFileDescriptorLimit(fd_limit);
  }
};

// static
BrowserMainParts* BrowserMainParts::CreateBrowserMainParts(
    const MainFunctionParams& parameters) {
  return new BrowserMainPartsPosix(parameters);
}