blob: 5c7ffd922082d5b8d6b47ca544326bf93102a273 [file] [log] [blame]
// Copyright 2017 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 "chrome/app/shutdown_signal_handlers_posix.h"
#include <limits.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include "base/callback.h"
#include "base/debug/leak_annotations.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/posix/eintr_wrapper.h"
#include "base/single_thread_task_runner.h"
#include "base/threading/platform_thread.h"
#include "base/threading/thread_task_runner_handle.h"
namespace {
// The OSX fork() implementation can crash in the child process before
// fork() returns. In that case, the shutdown pipe will still be
// shared with the parent process. To prevent child crashes from
// causing parent shutdowns, |g_pipe_pid| is the pid for the process
// which registered |g_shutdown_pipe_write_fd|.
// See <>.
pid_t g_pipe_pid = -1;
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_pipe_pid != -1);
RAW_CHECK(g_shutdown_pipe_write_fd != -1);
RAW_CHECK(g_shutdown_pipe_read_fd != -1);
RAW_CHECK(g_pipe_pid == getpid());
size_t bytes_written = 0;
do {
int rv = HANDLE_EINTR(
reinterpret_cast<const char*>(&signal) + bytes_written,
sizeof(signal) - bytes_written));
RAW_CHECK(rv >= 0);
bytes_written += rv;
} while (bytes_written < sizeof(signal));
void SIGHUPHandler(int signal) {
RAW_CHECK(signal == SIGHUP);
void SIGINTHandler(int signal) {
RAW_CHECK(signal == SIGINT);
void SIGTERMHandler(int signal) {
// Runs a thread that invokes a callback when a termination signal handler
// is invoked. Uses a pipe to wait for the signal handler to run.
class ShutdownDetector : public base::PlatformThread::Delegate {
int shutdown_fd,
const base::Closure& shutdown_callback,
const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
~ShutdownDetector() override;
// base::PlatformThread::Delegate:
void ThreadMain() override;
const int shutdown_fd_;
const base::Closure shutdown_callback_;
const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
int shutdown_fd,
const base::Closure& shutdown_callback,
const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
: shutdown_fd_(shutdown_fd),
task_runner_(task_runner) {
CHECK_NE(shutdown_fd_, -1);
ShutdownDetector::~ShutdownDetector() {}
// These functions are used to help us diagnose crash dumps that happen
// during the shutdown process.
NOINLINE void ShutdownFDReadError() {
// Ensure function isn't optimized away.
NOINLINE void ShutdownFDClosedError() {
// Ensure function isn't optimized away.
NOINLINE void ExitPosted() {
// Ensure function isn't optimized away.
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);
} else if (ret == 0) {
NOTREACHED() << "Unexpected closure of shutdown pipe.";
bytes_read += ret;
} while (bytes_read < sizeof(signal));
VLOG(1) << "Handling shutdown for signal " << signal << ".";
if (!task_runner_->PostTask(FROM_HERE, shutdown_callback_)) {
// Without a valid task runner 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 valid task runner, exiting ungracefully.");
kill(getpid(), signal);
// The signal may be handled on another thread. Give that a chance to
// happen.
// 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));
} // namespace
void InstallShutdownSignalHandlers(
const base::Closure& shutdown_callback,
const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
int pipefd[2];
int ret = pipe(pipefd);
if (ret < 0) {
PLOG(DFATAL) << "Failed to create pipe";
g_pipe_pid = getpid();
g_shutdown_pipe_read_fd = pipefd[0];
g_shutdown_pipe_write_fd = pipefd[1];
const size_t kShutdownDetectorThreadStackSize = PTHREAD_STACK_MIN * 2;
// ASan instrumentation and -finstrument-functions (used for keeping the
// shadow stacks) bloat the stack frames, so we need to increase the stack
// size to avoid hitting the guard page.
const size_t kShutdownDetectorThreadStackSize = PTHREAD_STACK_MIN * 4;
ShutdownDetector* detector = new ShutdownDetector(
g_shutdown_pipe_read_fd, shutdown_callback, task_runner);
// PlatformThread does not delete its delegate.
if (!base::PlatformThread::CreateNonJoinable(kShutdownDetectorThreadStackSize,
detector)) {
LOG(DFATAL) << "Failed to create shutdown detector task.";
// Setup signal handlers for shutdown AFTER shutdown pipe is setup because
// it may be called right away after handler is set.
// If adding to this list of signal handlers, note the new signal probably
// needs to be reset in child processes. See
// base/
// We need to handle SIGTERM, because that is how many POSIX-based distros
// ask processes to quit gracefully at shutdown time.
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_handler = SIGTERMHandler;
CHECK(sigaction(SIGTERM, &action, nullptr) == 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, nullptr) == 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, nullptr) == 0);