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Subprocess.cpp
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Subprocess.cpp
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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* 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.
*/
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <folly/Subprocess.h>
#if defined(__linux__)
#include <sys/prctl.h>
#endif
#include <fcntl.h>
#include <algorithm>
#include <array>
#include <system_error>
#include <thread>
#include <boost/container/flat_set.hpp>
#include <boost/range/adaptors.hpp>
#include <folly/Conv.h>
#include <folly/Exception.h>
#include <folly/ScopeGuard.h>
#include <folly/String.h>
#include <folly/io/Cursor.h>
#include <folly/lang/Assume.h>
#include <folly/logging/xlog.h>
#include <folly/portability/Dirent.h>
#include <folly/portability/Fcntl.h>
#include <folly/portability/Sockets.h>
#include <folly/portability/Stdlib.h>
#include <folly/portability/SysSyscall.h>
#include <folly/portability/Unistd.h>
#include <folly/system/AtFork.h>
#include <folly/system/Shell.h>
constexpr int kExecFailure = 127;
constexpr int kChildFailure = 126;
namespace folly {
ProcessReturnCode ProcessReturnCode::make(int status) {
if (!WIFEXITED(status) && !WIFSIGNALED(status)) {
throw std::runtime_error(
to<std::string>("Invalid ProcessReturnCode: ", status));
}
return ProcessReturnCode(status);
}
ProcessReturnCode::ProcessReturnCode(ProcessReturnCode&& p) noexcept
: rawStatus_(p.rawStatus_) {
p.rawStatus_ = ProcessReturnCode::RV_NOT_STARTED;
}
ProcessReturnCode& ProcessReturnCode::operator=(
ProcessReturnCode&& p) noexcept {
rawStatus_ = p.rawStatus_;
p.rawStatus_ = ProcessReturnCode::RV_NOT_STARTED;
return *this;
}
ProcessReturnCode::State ProcessReturnCode::state() const {
if (rawStatus_ == RV_NOT_STARTED) {
return NOT_STARTED;
}
if (rawStatus_ == RV_RUNNING) {
return RUNNING;
}
if (WIFEXITED(rawStatus_)) {
return EXITED;
}
if (WIFSIGNALED(rawStatus_)) {
return KILLED;
}
assume_unreachable();
}
void ProcessReturnCode::enforce(State expected) const {
State s = state();
if (s != expected) {
throw std::logic_error(to<std::string>(
"Bad use of ProcessReturnCode; state is ", s, " expected ", expected));
}
}
int ProcessReturnCode::exitStatus() const {
enforce(EXITED);
return WEXITSTATUS(rawStatus_);
}
int ProcessReturnCode::killSignal() const {
enforce(KILLED);
return WTERMSIG(rawStatus_);
}
bool ProcessReturnCode::coreDumped() const {
enforce(KILLED);
return WCOREDUMP(rawStatus_);
}
bool ProcessReturnCode::succeeded() const {
return exited() && exitStatus() == 0;
}
std::string ProcessReturnCode::str() const {
switch (state()) {
case NOT_STARTED:
return "not started";
case RUNNING:
return "running";
case EXITED:
return to<std::string>("exited with status ", exitStatus());
case KILLED:
return to<std::string>(
"killed by signal ",
killSignal(),
(coreDumped() ? " (core dumped)" : ""));
}
assume_unreachable();
}
CalledProcessError::CalledProcessError(ProcessReturnCode rc)
: SubprocessError(rc.str()), returnCode_(rc) {}
static inline std::string toSubprocessSpawnErrorMessage(
char const* executable, int errCode, int errnoValue) {
auto prefix = errCode == kExecFailure ? "failed to execute "
: "error preparing to execute ";
return to<std::string>(prefix, executable, ": ", errnoStr(errnoValue));
}
SubprocessSpawnError::SubprocessSpawnError(
const char* executable, int errCode, int errnoValue)
: SubprocessError(
toSubprocessSpawnErrorMessage(executable, errCode, errnoValue)),
errnoValue_(errnoValue) {}
namespace {
// Copy pointers to the given strings in a format suitable for posix_spawn
std::unique_ptr<const char*[]> cloneStrings(const std::vector<std::string>& s) {
std::unique_ptr<const char*[]> d(new const char*[s.size() + 1]);
for (size_t i = 0; i < s.size(); i++) {
d[i] = s[i].c_str();
}
d[s.size()] = nullptr;
return d;
}
// Check a wait() status, throw on non-successful
void checkStatus(ProcessReturnCode returnCode) {
if (returnCode.state() != ProcessReturnCode::EXITED ||
returnCode.exitStatus() != 0) {
throw CalledProcessError(returnCode);
}
}
} // namespace
Subprocess::Options& Subprocess::Options::fd(int fd, int action) {
if (action == Subprocess::PIPE) {
if (fd == 0) {
action = Subprocess::PIPE_IN;
} else if (fd == 1 || fd == 2) {
action = Subprocess::PIPE_OUT;
} else {
throw std::invalid_argument(
to<std::string>("Only fds 0, 1, 2 are valid for action=PIPE: ", fd));
}
}
fdActions_[fd] = action;
return *this;
}
Subprocess::Subprocess() = default;
Subprocess::Subprocess(
const std::vector<std::string>& argv,
const Options& options,
const char* executable,
const std::vector<std::string>* env)
: destroyBehavior_(options.destroyBehavior_) {
if (argv.empty()) {
throw std::invalid_argument("argv must not be empty");
}
if (!executable) {
executable = argv[0].c_str();
}
spawn(cloneStrings(argv), executable, options, env);
}
Subprocess::Subprocess(
const std::string& cmd,
const Options& options,
const std::vector<std::string>* env)
: destroyBehavior_(options.destroyBehavior_) {
if (options.usePath_) {
throw std::invalid_argument("usePath() not allowed when running in shell");
}
std::vector<std::string> argv = {"/bin/sh", "-c", cmd};
spawn(cloneStrings(argv), argv[0].c_str(), options, env);
}
Subprocess Subprocess::fromExistingProcess(pid_t pid) {
Subprocess sp;
sp.pid_ = pid;
sp.destroyBehavior_ = DestroyBehaviorLeak;
sp.returnCode_ = ProcessReturnCode::makeRunning();
return sp;
}
Subprocess::~Subprocess() {
if (returnCode_.state() == ProcessReturnCode::RUNNING) {
if (destroyBehavior_ == DestroyBehaviorFatal) {
// Explicitly crash if we are destroyed without reaping the child process.
//
// If you are running into this crash, you are destroying a Subprocess
// without cleaning up the child process first, which can leave behind a
// zombie process on the system until the current process exits. You may
// want to use one of the following options instead when creating the
// Subprocess:
// - Options::detach()
// If you do not want to wait on the child process to complete, and do
// not care about its exit status, use detach().
// - Options::killChildOnDestruction()
// If you want the child process to be automatically killed when the
// Subprocess is destroyed, use killChildOnDestruction() or
// terminateChildOnDestruction()
XLOG(FATAL) << "Subprocess destroyed without reaping child";
} else if (destroyBehavior_ == DestroyBehaviorLeak) {
// Do nothing if we are destroyed without reaping the child process.
XLOG(DBG) << "Subprocess destroyed without reaping child process";
} else {
// If we are killed without reaping the child process, explicitly
// terminate/kill it and wait for it to exit.
try {
TimeoutDuration timeout(destroyBehavior_);
terminateOrKill(timeout);
} catch (const std::exception& ex) {
XLOG(WARN) << "error terminating process in Subprocess destructor: "
<< ex.what();
}
}
}
}
namespace {
struct ChildErrorInfo {
int errCode;
int errnoValue;
};
[[noreturn]] void childError(int errFd, int errCode, int errnoValue) {
ChildErrorInfo info = {errCode, errnoValue};
// Write the error information over the pipe to our parent process.
// We can't really do anything else if this write call fails.
writeNoInt(errFd, &info, sizeof(info));
// exit
_exit(errCode);
}
} // namespace
void Subprocess::setAllNonBlocking() {
for (auto& p : pipes_) {
int fd = p.pipe.fd();
int flags = ::fcntl(fd, F_GETFL);
checkUnixError(flags, "fcntl");
int r = ::fcntl(fd, F_SETFL, flags | O_NONBLOCK);
checkUnixError(r, "fcntl");
}
}
void Subprocess::spawn(
std::unique_ptr<const char*[]> argv,
const char* executable,
const Options& optionsIn,
const std::vector<std::string>* env) {
if (optionsIn.usePath_ && env) {
throw std::invalid_argument(
"usePath() not allowed when overriding environment");
}
// Make a copy, we'll mutate options
Options options(optionsIn);
// On error, close all pipes_ (ignoring errors, but that seems fine here).
auto pipesGuard = makeGuard([this] { pipes_.clear(); });
// Create a pipe to use to receive error information from the child,
// in case it fails before calling exec()
int errFds[2];
#if FOLLY_HAVE_PIPE2
checkUnixError(::pipe2(errFds, O_CLOEXEC), "pipe2");
#else
checkUnixError(::pipe(errFds), "pipe");
#endif
SCOPE_EXIT {
CHECK_ERR(::close(errFds[0]));
if (errFds[1] >= 0) {
CHECK_ERR(::close(errFds[1]));
}
};
#if !FOLLY_HAVE_PIPE2
// Ask the child to close the read end of the error pipe.
checkUnixError(fcntl(errFds[0], F_SETFD, FD_CLOEXEC), "set FD_CLOEXEC");
// Set the close-on-exec flag on the write side of the pipe.
// This way the pipe will be closed automatically in the child if execve()
// succeeds. If the exec fails the child can write error information to the
// pipe.
checkUnixError(fcntl(errFds[1], F_SETFD, FD_CLOEXEC), "set FD_CLOEXEC");
#endif
// Perform the actual work of setting up pipes then forking and
// executing the child.
spawnInternal(std::move(argv), executable, options, env, errFds[1]);
// After spawnInternal() returns the child is alive. We have to be very
// careful about throwing after this point. We are inside the constructor,
// so if we throw the Subprocess object will have never existed, and the
// destructor will never be called.
//
// We should only throw if we got an error via the errFd, and we know the
// child has exited and can be immediately waited for. In all other cases,
// we have no way of cleaning up the child.
// Close writable side of the errFd pipe in the parent process
CHECK_ERR(::close(errFds[1]));
errFds[1] = -1;
// Read from the errFd pipe, to tell if the child ran into any errors before
// calling exec()
readChildErrorPipe(errFds[0], executable);
// If we spawned a detached child, wait on the intermediate child process.
// It always exits immediately.
if (options.detach_) {
wait();
}
// We have fully succeeded now, so release the guard on pipes_
pipesGuard.dismiss();
}
// With -Wclobbered, gcc complains about vfork potentially cloberring the
// childDir variable, even though we only use it on the child side of the
// vfork.
FOLLY_PUSH_WARNING
FOLLY_GCC_DISABLE_WARNING("-Wclobbered")
void Subprocess::spawnInternal(
std::unique_ptr<const char*[]> argv,
const char* executable,
Options& options,
const std::vector<std::string>* env,
int errFd) {
// Parent work, pre-fork: create pipes
std::vector<int> childFds;
// Close all of the childFds as we leave this scope
SCOPE_EXIT {
// These are only pipes, closing them shouldn't fail
for (int cfd : childFds) {
CHECK_ERR(::close(cfd));
}
};
int r;
for (auto& p : options.fdActions_) {
if (p.second == PIPE_IN || p.second == PIPE_OUT) {
int fds[2];
// We're setting both ends of the pipe as close-on-exec. The child
// doesn't need to reset the flag on its end, as we always dup2() the fd,
// and dup2() fds don't share the close-on-exec flag.
#if FOLLY_HAVE_PIPE2
// If possible, set close-on-exec atomically. Otherwise, a concurrent
// Subprocess invocation can fork() between "pipe" and "fnctl",
// causing FDs to leak.
r = ::pipe2(fds, O_CLOEXEC);
checkUnixError(r, "pipe2");
#else
r = ::pipe(fds);
checkUnixError(r, "pipe");
r = fcntl(fds[0], F_SETFD, FD_CLOEXEC);
checkUnixError(r, "set FD_CLOEXEC");
r = fcntl(fds[1], F_SETFD, FD_CLOEXEC);
checkUnixError(r, "set FD_CLOEXEC");
#endif
pipes_.emplace_back();
Pipe& pipe = pipes_.back();
pipe.direction = p.second;
int cfd;
if (p.second == PIPE_IN) {
// Child gets reading end
pipe.pipe = folly::File(fds[1], /*ownsFd=*/true);
cfd = fds[0];
} else {
pipe.pipe = folly::File(fds[0], /*ownsFd=*/true);
cfd = fds[1];
}
p.second = cfd; // ensure it gets dup2()ed
pipe.childFd = p.first;
childFds.push_back(cfd);
}
}
// This should already be sorted, as options.fdActions_ is
DCHECK(std::is_sorted(pipes_.begin(), pipes_.end()));
// Note that the const casts below are legit, per
// http://pubs.opengroup.org/onlinepubs/009695399/functions/exec.html
auto argVec = const_cast<char**>(argv.get());
// Set up environment
std::unique_ptr<const char*[]> envHolder;
char** envVec;
if (env) {
envHolder = cloneStrings(*env);
envVec = const_cast<char**>(envHolder.get());
} else {
envVec = environ;
}
// Block all signals around vfork; see http://ewontfix.com/7/.
//
// As the child may run in the same address space as the parent until
// the actual execve() system call, any (custom) signal handlers that
// the parent has might alter parent's memory if invoked in the child,
// with undefined results. So we block all signals in the parent before
// vfork(), which will cause them to be blocked in the child as well (we
// rely on the fact that Linux, just like all sane implementations, only
// clones the calling thread). Then, in the child, we reset all signals
// to their default dispositions (while still blocked), and unblock them
// (so the exec()ed process inherits the parent's signal mask)
//
// The parent also unblocks all signals as soon as vfork() returns.
sigset_t allBlocked;
r = sigfillset(&allBlocked);
checkUnixError(r, "sigfillset");
sigset_t oldSignals;
r = pthread_sigmask(SIG_SETMASK, &allBlocked, &oldSignals);
checkPosixError(r, "pthread_sigmask");
SCOPE_EXIT {
// Restore signal mask
r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
CHECK_EQ(r, 0) << "pthread_sigmask: " << errnoStr(r); // shouldn't fail
};
// Call c_str() here, as it's not necessarily safe after fork.
const char* childDir =
options.childDir_.empty() ? nullptr : options.childDir_.c_str();
pid_t pid;
#ifdef __linux__
if (options.cloneFlags_) {
pid = syscall(SYS_clone, *options.cloneFlags_, 0, nullptr, nullptr);
} else {
#endif
if (options.detach_) {
// If we are detaching we must use fork() instead of vfork() for the first
// fork, since we aren't going to simply call exec() in the child.
pid = AtFork::forkInstrumented(fork);
} else {
if (kIsSanitizeThread) {
// TSAN treats vfork as fork, so use the instrumented version
// instead
pid = AtFork::forkInstrumented(fork);
} else {
pid = vfork();
}
}
#ifdef __linux__
}
#endif
checkUnixError(pid, errno, "failed to fork");
if (pid == 0) {
// Fork a second time if detach_ was requested.
// This must be done before signals are restored in prepareChild()
if (options.detach_) {
#ifdef __linux__
if (options.cloneFlags_) {
pid = syscall(SYS_clone, *options.cloneFlags_, 0, nullptr, nullptr);
} else {
#endif
if (kIsSanitizeThread) {
// TSAN treats vfork as fork, so use the instrumented version
// instead
pid = AtFork::forkInstrumented(fork);
} else {
pid = vfork();
}
#ifdef __linux__
}
#endif
if (pid == -1) {
// Inform our parent process of the error so it can throw in the parent.
childError(errFd, kChildFailure, errno);
} else if (pid != 0) {
// We are the intermediate process. Exit immediately.
// Our child will still inform the original parent of success/failure
// through errFd. The pid of the grandchild process never gets
// propagated back up to the original parent. In the future we could
// potentially send it back using errFd if we needed to.
_exit(0);
}
}
int errnoValue = prepareChild(options, &oldSignals, childDir);
if (errnoValue != 0) {
childError(errFd, kChildFailure, errnoValue);
}
errnoValue = runChild(executable, argVec, envVec, options);
// If we get here, exec() failed.
childError(errFd, kExecFailure, errnoValue);
}
// Child is alive. We have to be very careful about throwing after this
// point. We are inside the constructor, so if we throw the Subprocess
// object will have never existed, and the destructor will never be called.
//
// We should only throw if we got an error via the errFd, and we know the
// child has exited and can be immediately waited for. In all other cases,
// we have no way of cleaning up the child.
pid_ = pid;
returnCode_ = ProcessReturnCode::makeRunning();
}
FOLLY_POP_WARNING
// If requested, close all other file descriptors. Don't close
// any fds in options.fdActions_, and don't touch stdin, stdout, stderr.
// Ignore errors.
//
//
// This function is called in the child after fork but before exec so
// there is very little it can do. It cannot allocate memory and
// it cannot lock a mutex, just as if it were running in a signal
// handler.
void Subprocess::closeInheritedFds(const Options::FdMap& fdActions) {
#if defined(__linux__)
int dirfd = open("/proc/self/fd", O_RDONLY);
if (dirfd != -1) {
char buffer[32768];
int res;
while ((res = syscall(SYS_getdents64, dirfd, buffer, sizeof(buffer))) > 0) {
// linux_dirent64 is part of the kernel ABI for the getdents64 system
// call. It is currently the same as struct dirent64 in both glibc and
// musl, but those are library specific and could change. linux_dirent64
// is not defined in the standard set of Linux userspace headers
// (/usr/include/linux)
//
// We do not use the POSIX interfaces (opendir, readdir, etc..) for
// reading a directory since they may allocate memory / grab a lock, which
// is unsafe in this context.
struct linux_dirent64 {
uint64_t d_ino;
int64_t d_off;
uint16_t d_reclen;
unsigned char d_type;
char d_name[0];
} const* entry;
for (int offset = 0; offset < res; offset += entry->d_reclen) {
entry = reinterpret_cast<struct linux_dirent64*>(buffer + offset);
if (entry->d_type != DT_LNK) {
continue;
}
char* end_p = nullptr;
errno = 0;
int fd = static_cast<int>(::strtol(entry->d_name, &end_p, 10));
if (errno == ERANGE || fd < 3 || end_p == entry->d_name) {
continue;
}
if ((fd != dirfd) && (fdActions.count(fd) == 0)) {
::close(fd);
}
}
}
::close(dirfd);
return;
}
#endif
// If not running on Linux or if we failed to open /proc/self/fd, try to close
// all possible open file descriptors.
for (int fd = sysconf(_SC_OPEN_MAX) - 1; fd >= 3; --fd) {
if (fdActions.count(fd) == 0) {
::close(fd);
}
}
}
int Subprocess::prepareChild(
const Options& options,
const sigset_t* sigmask,
const char* childDir) const {
// While all signals are blocked, we must reset their
// dispositions to default.
for (int sig = 1; sig < NSIG; ++sig) {
::signal(sig, SIG_DFL);
}
{
// Unblock signals; restore signal mask.
int r = pthread_sigmask(SIG_SETMASK, sigmask, nullptr);
if (r != 0) {
return r; // pthread_sigmask() returns an errno value
}
}
// Change the working directory, if one is given
if (childDir) {
if (::chdir(childDir) == -1) {
return errno;
}
}
#ifdef __linux__
// Best effort
if (options.cpuSet_.hasValue()) {
const auto& cpuSet = options.cpuSet_.value();
::sched_setaffinity(0, sizeof(cpuSet), &cpuSet);
}
#endif
// We don't have to explicitly close the parent's end of all pipes,
// as they all have the FD_CLOEXEC flag set and will be closed at
// exec time.
// Redirect requested FDs to /dev/null or NUL
// dup2 any explicitly specified FDs
for (auto& p : options.fdActions_) {
if (p.second == DEV_NULL) {
// folly/portability/Fcntl provides an impl of open that will
// map this to NUL on Windows.
auto devNull = ::open("/dev/null", O_RDWR | O_CLOEXEC);
if (devNull == -1) {
return errno;
}
// note: dup2 will not set CLOEXEC on the destination
if (::dup2(devNull, p.first) == -1) {
// explicit close on error to avoid leaking fds
::close(devNull);
return errno;
}
::close(devNull);
} else if (p.second != p.first) {
if (::dup2(p.second, p.first) == -1) {
return errno;
}
}
}
if (options.closeOtherFds_) {
closeInheritedFds(options.fdActions_);
}
#if defined(__linux__)
// Opt to receive signal on parent death, if requested
if (options.parentDeathSignal_ != 0) {
const auto parentDeathSignal =
static_cast<unsigned long>(options.parentDeathSignal_);
if (prctl(PR_SET_PDEATHSIG, parentDeathSignal, 0, 0, 0) == -1) {
return errno;
}
}
#endif
if (options.processGroupLeader_) {
#if !defined(__FreeBSD__)
if (setpgrp() == -1) {
#else
if (setpgrp(getpid(), getpgrp()) == -1) {
#endif
return errno;
}
}
// The user callback comes last, so that the child is otherwise all set up.
if (options.dangerousPostForkPreExecCallback_) {
if (int error = (*options.dangerousPostForkPreExecCallback_)()) {
return error;
}
}
return 0;
}
int Subprocess::runChild(
const char* executable,
char** argv,
char** env,
const Options& options) const {
// Now, finally, exec.
if (options.usePath_) {
::execvp(executable, argv);
} else {
::execve(executable, argv, env);
}
return errno;
}
void Subprocess::readChildErrorPipe(int pfd, const char* executable) {
ChildErrorInfo info;
auto rc = readNoInt(pfd, &info, sizeof(info));
if (rc == 0) {
// No data means the child executed successfully, and the pipe
// was closed due to the close-on-exec flag being set.
return;
} else if (rc != sizeof(ChildErrorInfo)) {
// An error occurred trying to read from the pipe, or we got a partial read.
// Neither of these cases should really occur in practice.
//
// We can't get any error data from the child in this case, and we don't
// know if it is successfully running or not. All we can do is to return
// normally, as if the child executed successfully. If something bad
// happened the caller should at least get a non-normal exit status from
// the child.
XLOGF(
ERR,
"unexpected error trying to read from child error pipe rc={}, errno={}",
rc,
errno);
return;
}
// We got error data from the child. The child should exit immediately in
// this case, so wait on it to clean up.
wait();
// Throw to signal the error
throw SubprocessSpawnError(executable, info.errCode, info.errnoValue);
}
ProcessReturnCode Subprocess::poll(struct rusage* ru) {
returnCode_.enforce(ProcessReturnCode::RUNNING);
DCHECK_GT(pid_, 0);
int status;
pid_t found = ::wait4(pid_, &status, WNOHANG, ru);
// The spec guarantees that EINTR does not occur with WNOHANG, so the only
// two remaining errors are ECHILD (other code reaped the child?), or
// EINVAL (cosmic rays?), both of which merit an abort:
PCHECK(found != -1) << "waitpid(" << pid_ << ", &status, WNOHANG)";
if (found != 0) {
// Though the child process had quit, this call does not close the pipes
// since its descendants may still be using them.
returnCode_ = ProcessReturnCode::make(status);
pid_ = -1;
}
return returnCode_;
}
bool Subprocess::pollChecked() {
if (poll().state() == ProcessReturnCode::RUNNING) {
return false;
}
checkStatus(returnCode_);
return true;
}
ProcessReturnCode Subprocess::wait() {
returnCode_.enforce(ProcessReturnCode::RUNNING);
DCHECK_GT(pid_, 0);
int status;
pid_t found;
do {
found = ::waitpid(pid_, &status, 0);
} while (found == -1 && errno == EINTR);
// The only two remaining errors are ECHILD (other code reaped the
// child?), or EINVAL (cosmic rays?), and both merit an abort:
PCHECK(found != -1) << "waitpid(" << pid_ << ", &status, 0)";
// Though the child process had quit, this call does not close the pipes
// since its descendants may still be using them.
DCHECK_EQ(found, pid_);
returnCode_ = ProcessReturnCode::make(status);
pid_ = -1;
return returnCode_;
}
void Subprocess::waitChecked() {
wait();
checkStatus(returnCode_);
}
ProcessReturnCode Subprocess::waitTimeout(TimeoutDuration timeout) {
returnCode_.enforce(ProcessReturnCode::RUNNING);
DCHECK_GT(pid_, 0) << "The subprocess has been waited already";
auto pollUntil = std::chrono::steady_clock::now() + timeout;
auto sleepDuration = std::chrono::milliseconds{2};
constexpr auto maximumSleepDuration = std::chrono::milliseconds{100};
for (;;) {
// Always call waitpid once after the full timeout has elapsed.
auto now = std::chrono::steady_clock::now();
int status;
pid_t found;
do {
found = ::waitpid(pid_, &status, WNOHANG);
} while (found == -1 && errno == EINTR);
PCHECK(found != -1) << "waitpid(" << pid_ << ", &status, WNOHANG)";
if (found) {
// Just on the safe side, make sure it's the actual pid we are waiting.
DCHECK_EQ(found, pid_);
returnCode_ = ProcessReturnCode::make(status);
// Change pid_ to -1 to detect programming error like calling
// this method multiple times.
pid_ = -1;
return returnCode_;
}
if (now > pollUntil) {
// Timed out: still running().
return returnCode_;
}
// The subprocess is still running, sleep for increasing periods of time.
std::this_thread::sleep_for(sleepDuration);
sleepDuration =
std::min(maximumSleepDuration, sleepDuration + sleepDuration);
}
}
void Subprocess::sendSignal(int signal) {
returnCode_.enforce(ProcessReturnCode::RUNNING);
int r = ::kill(pid_, signal);
checkUnixError(r, "kill");
}
ProcessReturnCode Subprocess::waitOrTerminateOrKill(
TimeoutDuration waitTimeout, TimeoutDuration sigtermTimeout) {
returnCode_.enforce(ProcessReturnCode::RUNNING);
DCHECK_GT(pid_, 0) << "The subprocess has been waited already";
this->waitTimeout(waitTimeout);
if (returnCode_.running()) {
return terminateOrKill(sigtermTimeout);
}
return returnCode_;
}
ProcessReturnCode Subprocess::terminateOrKill(TimeoutDuration sigtermTimeout) {
returnCode_.enforce(ProcessReturnCode::RUNNING);
DCHECK_GT(pid_, 0) << "The subprocess has been waited already";
if (sigtermTimeout > TimeoutDuration(0)) {
// 1. Send SIGTERM to kill the process
terminate();
// 2. check whether subprocess has terminated using non-blocking waitpid
waitTimeout(sigtermTimeout);
if (!returnCode_.running()) {
return returnCode_;
}
}
// 3. If we are at this point, we have waited enough time after
// sending SIGTERM, we have to use nuclear option SIGKILL to kill
// the subprocess.
XLOGF(INFO, "Send SIGKILL to {}", pid_);
kill();
// 4. SIGKILL should kill the process otherwise there must be
// something seriously wrong, just use blocking wait to wait for the
// subprocess to finish.
return wait();
}
pid_t Subprocess::pid() const {
return pid_;
}
namespace {
ByteRange queueFront(const IOBufQueue& queue) {
auto* p = queue.front();
if (!p) {
return ByteRange{};
}
return io::Cursor(p).peekBytes();
}
// fd write
bool handleWrite(int fd, IOBufQueue& queue) {
for (;;) {
auto b = queueFront(queue);
if (b.empty()) {
return true; // EOF
}
ssize_t n = writeNoInt(fd, b.data(), b.size());
if (n == -1 && errno == EAGAIN) {
return false;
}
checkUnixError(n, "write");
queue.trimStart(n);
}
}
// fd read
bool handleRead(int fd, IOBufQueue& queue) {
for (;;) {
auto p = queue.preallocate(100, 65000);
ssize_t n = readNoInt(fd, p.first, p.second);
if (n == -1 && errno == EAGAIN) {
return false;
}
checkUnixError(n, "read");
if (n == 0) {
return true;
}
queue.postallocate(n);
}
}
bool discardRead(int fd) {
static const size_t bufSize = 65000;
// Thread unsafe, but it doesn't matter.
static std::unique_ptr<char[]> buf(new char[bufSize]);
for (;;) {
ssize_t n = readNoInt(fd, buf.get(), bufSize);
if (n == -1 && errno == EAGAIN) {
return false;
}
checkUnixError(n, "read");
if (n == 0) {
return true;
}
}
}
} // namespace
std::pair<std::string, std::string> Subprocess::communicate(StringPiece input) {
IOBufQueue inputQueue;
inputQueue.wrapBuffer(input.data(), input.size());
auto outQueues = communicateIOBuf(std::move(inputQueue));
auto outBufs =
std::make_pair(outQueues.first.move(), outQueues.second.move());
std::pair<std::string, std::string> out;
if (outBufs.first) {
outBufs.first->coalesce();
out.first.assign(
reinterpret_cast<const char*>(outBufs.first->data()),
outBufs.first->length());
}
if (outBufs.second) {
outBufs.second->coalesce();
out.second.assign(
reinterpret_cast<const char*>(outBufs.second->data()),
outBufs.second->length());
}
return out;
}
std::pair<IOBufQueue, IOBufQueue> Subprocess::communicateIOBuf(
IOBufQueue input) {
// If the user supplied a non-empty input buffer, make sure
// that stdin is a pipe so we can write the data.
if (!input.empty()) {
// findByChildFd() will throw std::invalid_argument if no pipe for
// STDIN_FILENO exists
findByChildFd(STDIN_FILENO);
}
std::pair<IOBufQueue, IOBufQueue> out;
auto readCallback = [&](int pfd, int cfd) -> bool {
if (cfd == STDOUT_FILENO) {
return handleRead(pfd, out.first);
} else if (cfd == STDERR_FILENO) {
return handleRead(pfd, out.second);
} else {
// Don't close the file descriptor, the child might not like SIGPIPE,
// just read and throw the data away.
return discardRead(pfd);
}
};
auto writeCallback = [&](int pfd, int cfd) -> bool {
if (cfd == STDIN_FILENO) {
return handleWrite(pfd, input);
} else {