use libc::c_int;
use crate::FromEnvErrorInner;
use std::fs::{File, OpenOptions};
use std::io::{self, Read, Write};
use std::mem;
use std::mem::MaybeUninit;
use std::os::unix::prelude::*;
use std::path::Path;
use std::process::Command;
use std::ptr;
use std::sync::{
atomic::{AtomicBool, Ordering},
Arc, Once,
};
use std::thread::{self, Builder, JoinHandle};
use std::time::Duration;
#[derive(Debug)]
/// This preserves the `--jobserver-auth` type at creation time,
/// so auth type will be passed down to and inherit from sub-Make processes correctly.
///
/// See <
https://github.com/rust-lang/jobserver-rs/issues/99> for details.
enum ClientCreationArg {
Fds { read: c_int, write: c_int },
Fifo(Box<Path>),
}
#[derive(Debug)]
pub struct Client {
read: File,
write: File,
creation_arg: ClientCreationArg,
/// It is set to `None` if the pipe is shared with other processes, so it
/// cannot support non-blocking mode.
///
/// If it is set to `Some`, then it can only go from
/// `Some(false)` -> `Some(true)` but not the other way around,
/// since that could cause a race condition.
is_non_blocking: Option<AtomicBool>,
}
#[derive(Debug)]
pub struct Acquired {
byte: u8,
}
impl Client {
pub fn new(mut limit: usize) -> io::Result<Client> {
let client = unsafe { Client::mk()? };
// I don't think the character written here matters, but I could be
// wrong!
const BUFFER: [u8; 128] = [b'|'; 128];
let mut write = &client.write;
set_nonblocking(write.as_raw_fd(), true)?;
while limit > 0 {
let n = limit.min(BUFFER.len());
write.write_all(&BUFFER[..n])?;
limit -= n;
}
set_nonblocking(write.as_raw_fd(), false)?;
Ok(client)
}
unsafe fn mk() -> io::Result<Client> {
let mut pipes = [0; 2];
// Attempt atomically-create-with-cloexec if we can on Linux,
// detected by using the `syscall` function in `libc` to try to work
// with as many kernels/glibc implementations as possible.
#[cfg(target_os = "linux")]
{
static PIPE2_AVAILABLE: AtomicBool = AtomicBool::new(true);
if PIPE2_AVAILABLE.load(Ordering::SeqCst) {
match libc::syscall(libc::SYS_pipe2, pipes.as_mut_ptr(), libc::O_CLOEXEC) {
-1 => {
let err = io::Error::last_os_error();
if err.raw_os_error() == Some(libc::ENOSYS) {
PIPE2_AVAILABLE.store(false, Ordering::SeqCst);
} else {
return Err(err);
}
}
_ => return Ok(Client::from_fds(pipes[0], pipes[1])),
}
}
}
cvt(libc::pipe(pipes.as_mut_ptr()))?;
drop(set_cloexec(pipes[0], true));
drop(set_cloexec(pipes[1], true));
Ok(Client::from_fds(pipes[0], pipes[1]))
}
pub(crate) unsafe fn open(s: &str, check_pipe: bool) -> Result<Client, FromEnvErrorInner> {
if let Some(client) = Self::from_fifo(s)? {
return Ok(client);
}
if let Some(client) = Self::from_pipe(s, check_pipe)? {
return Ok(client);
}
Err(FromEnvErrorInner::CannotParse(format!(
"expected `fifo:PATH` or `R,W`, found `{s}`"
)))
}
/// `--jobserver-auth=fifo:PATH`
fn from_fifo(s: &str) -> Result<Option<Client>, FromEnvErrorInner> {
let mut parts = s.splitn(2, ':');
if parts.next().unwrap() != "fifo" {
return Ok(None);
}
let path_str = parts.next().ok_or_else(|| {
FromEnvErrorInner::CannotParse("expected a path after `fifo:`".to_string())
})?;
let path = Path::new(path_str);
let open_file = || {
// Opening with read write is necessary, since opening with
// read-only or write-only could block the thread until another
// thread opens it with write-only or read-only (or RDWR)
// correspondingly.
OpenOptions::new()
.read(true)
.write(true)
.open(path)
.map_err(|err| FromEnvErrorInner::CannotOpenPath(path_str.to_string(), err))
};
Ok(Some(Client {
read: open_file()?,
write: open_file()?,
creation_arg: ClientCreationArg::Fifo(path.into()),
is_non_blocking: Some(AtomicBool::new(false)),
}))
}
/// `--jobserver-auth=R,W`
unsafe fn from_pipe(s: &str, check_pipe: bool) -> Result<Option<Client>, FromEnvErrorInner> {
let mut parts = s.splitn(2, ',');
let read = parts.next().unwrap();
let write = match parts.next() {
Some(w) => w,
None => return Ok(None),
};
let read = read
.parse()
.map_err(|e| FromEnvErrorInner::CannotParse(format!("cannot parse `read` fd: {e}")))?
;
let write = write
.parse()
.map_err(|e| FromEnvErrorInner::CannotParse(format!("cannot parse `write` fd: {e}")))?;
// If either or both of these file descriptors are negative,
// it means the jobserver is disabled for this process.
if read < 0 {
return Err(FromEnvErrorInner::NegativeFd(read));
}
if write < 0 {
return Err(FromEnvErrorInner::NegativeFd(write));
}
let creation_arg = ClientCreationArg::Fds { read, write };
// Ok so we've got two integers that look like file descriptors, but
// for extra sanity checking let's see if they actually look like
// valid files and instances of a pipe if feature enabled before we
// return the client.
//
// If we're called from `make` *without* the leading + on our rule
// then we'll have `MAKEFLAGS` env vars but won't actually have
// access to the file descriptors.
//
// `NotAPipe` is a worse error, return it if it's reported for any of the two fds.
match (fd_check(read, check_pipe), fd_check(write, check_pipe)) {
(read_err @ Err(FromEnvErrorInner::NotAPipe(..)), _) => read_err?,
(_, write_err @ Err(FromEnvErrorInner::NotAPipe(..))) => write_err?,
(read_err, write_err) => {
read_err?;
write_err?;
// Optimization: Try converting it to a fifo by using /dev/fd
//
// On linux, opening `/dev/fd/$fd` returns a fd with a new file description,
// so we can set `O_NONBLOCK` on it without affecting other processes.
//
// On macOS, opening `/dev/fd/$fd` seems to be the same as `File::try_clone`.
//
// I tested this on macOS 14 and Linux 6.5.13
#[cfg(target_os = "linux")]
if let (Ok(read), Ok(write)) = (
File::open(format!("/dev/fd/{}", read)),
OpenOptions::new()
.write(true)
.open(format!("/dev/fd/{}", write)),
) {
return Ok(Some(Client {
read,
write,
creation_arg,
is_non_blocking: Some(AtomicBool::new(false)),
}));
}
}
}
Ok(Some(Client {
read: clone_fd_and_set_cloexec(read)?,
write: clone_fd_and_set_cloexec(write)?,
creation_arg,
is_non_blocking: None,
}))
}
unsafe fn from_fds(read: c_int, write: c_int) -> Client {
Client {
read: File::from_raw_fd(read),
write: File::from_raw_fd(write),
creation_arg: ClientCreationArg::Fds { read, write },
is_non_blocking: None,
}
}
pub fn acquire(&self) -> io::Result<Acquired> {
// Ignore interrupts and keep trying if that happens
loop {
if let Some(token) = self.acquire_allow_interrupts()? {
return Ok(token);
}
}
}
/// Block waiting for a token, returning `None` if we're interrupted with
/// EINTR.
fn acquire_allow_interrupts(&self) -> io::Result<Option<Acquired>> {
// We don't actually know if the file descriptor here is set in
// blocking or nonblocking mode. AFAIK all released versions of
// `make` use blocking fds for the jobserver, but the unreleased
// version of `make` doesn't. In the unreleased version jobserver
// fds are set to nonblocking and combined with `pselect`
// internally.
//
// Here we try to be compatible with both strategies. We optimistically
// try to read from the file descriptor which then may block, return
// a token or indicate that polling is needed.
// Blocking reads (if possible) allows the kernel to be more selective
// about which readers to wake up when a token is written to the pipe.
//
// We use `poll` here to block this thread waiting for read
// readiness, and then afterwards we perform the `read` itself. If
// the `read` returns that it would block then we start over and try
// again.
//
// Also note that we explicitly don't handle EINTR here. That's used
// to shut us down, so we otherwise punt all errors upwards.
unsafe {
let mut fd: libc::pollfd = mem::zeroed();
let mut read = &self.read;
fd.fd = read.as_raw_fd();
fd.events = libc::POLLIN;
loop {
let mut buf = [0];
match read.read(&mut buf) {
Ok(1) => return Ok(Some(Acquired { byte: buf[0] })),
Ok(_) => {
return Err(io::Error::new(
io::ErrorKind::UnexpectedEof,
"early EOF on jobserver pipe",
));
}
Err(e) => match e.kind() {
io::ErrorKind::WouldBlock => { /* fall through to polling */ }
io::ErrorKind::Interrupted => return Ok(None),
_ => return Err(e),
},
}
loop {
fd.revents = 0;
if libc::poll(&mut fd, 1, -1) == -1 {
let e = io::Error::last_os_error();
return match e.kind() {
io::ErrorKind::Interrupted => Ok(None),
_ => Err(e),
};
}
if fd.revents != 0 {
break;
}
}
}
}
}
pub fn try_acquire(&self) -> io::Result<Option<Acquired>> {
let mut buf = [0];
let mut fifo = &self.read;
if let Some(is_non_blocking) = self.is_non_blocking.as_ref() {
if !is_non_blocking.load(Ordering::Relaxed) {
set_nonblocking(fifo.as_raw_fd(), true)?;
is_non_blocking.store(true, Ordering::Relaxed);
}
} else {
return Err(io::ErrorKind::Unsupported.into());
}
loop {
match fifo.read(&mut buf) {
Ok(1) => break Ok(Some(Acquired { byte: buf[0] })),
Ok(_) => {
break Err(io::Error::new(
io::ErrorKind::UnexpectedEof,
"early EOF on jobserver pipe",
))
}
Err(e) if e.kind() == io::ErrorKind::WouldBlock => break Ok(None),
Err(e) if e.kind() == io::ErrorKind::Interrupted => continue,
Err(err) => break Err(err),
}
}
}
pub fn release(&self, data: Option<&Acquired>) -> io::Result<()> {
// Note that the fd may be nonblocking but we're going to go ahead
// and assume that the writes here are always nonblocking (we can
// always quickly release a token). If that turns out to not be the
// case we'll get an error anyway!
let byte = data.map(|d| d.byte).unwrap_or(b'+');
match (&self.write).write(&[byte])? {
1 => Ok(()),
_ => Err(io::Error::new(
io::ErrorKind::Other,
"failed to write token back to jobserver",
)),
}
}
pub fn string_arg(&self) -> String {
match &self.creation_arg {
ClientCreationArg::Fifo(path) => format!("fifo:{}", path.display()),
ClientCreationArg::Fds { read, write } => format!("{},{}", read, write),
}
}
pub fn available(&self) -> io::Result<usize> {
let mut len = MaybeUninit::<c_int>::uninit();
cvt(unsafe { libc::ioctl(self.read.as_raw_fd(), libc::FIONREAD, len.as_mut_ptr()) })?;
Ok(unsafe { len.assume_init() } as usize)
}
pub fn configure(&self, cmd: &mut Command) {
if matches!(self.creation_arg, ClientCreationArg::Fifo { .. }) {
// We `File::open`ed it when inheriting from environment,
// so no need to set cloexec for fifo.
return;
}
// Here we basically just want to say that in the child process
// we'll configure the read/write file descriptors to *not* be
// cloexec, so they're inherited across the exec and specified as
// integers through `string_arg` above.
let read = self.read.as_raw_fd();
let write = self.write.as_raw_fd();
unsafe {
cmd.pre_exec(move || {
set_cloexec(read, false)?;
set_cloexec(write, false)?;
Ok(())
});
}
}
}
#[derive(Debug)]
pub struct Helper {
thread: JoinHandle<()>,
state: Arc<super::HelperState>,
}
pub(crate) fn spawn_helper(
client: crate::Client,
state: Arc<super::HelperState>,
mut f: Box<dyn FnMut(io::Result<crate::Acquired>) + Send>,
) -> io::Result<Helper> {
static USR1_INIT: Once = Once::new();
let mut err = None;
USR1_INIT.call_once(|| unsafe {
let mut new: libc::sigaction = mem::zeroed();
#[cfg(target_os = "aix")]
{
new.sa_union.__su_sigaction = sigusr1_handler;
}
#[cfg(not(target_os = "aix"))]
{
new.sa_sigaction = sigusr1_handler as usize;
}
new.sa_flags = libc::SA_SIGINFO as _;
if libc::sigaction(libc::SIGUSR1, &new, ptr::null_mut()) != 0 {
err = Some(io::Error::last_os_error());
}
});
if let Some(e) = err.take() {
return Err(e);
}
let state2 = state.clone();
let thread = Builder::new().spawn(move || {
state2.for_each_request(|helper| loop {
match client.inner.acquire_allow_interrupts() {
Ok(Some(data)) => {
break f(Ok(crate::Acquired {
client: client.inner.clone(),
data,
disabled: false,
}));
}
Err(e) => break f(Err(e)),
Ok(None) if helper.lock().producer_done => break,
Ok(None) => {}
}
});
})?;
Ok(Helper { thread, state })
}
impl Helper {
pub fn join(self) {
let dur = Duration::from_millis(10);
let mut state = self.state.lock();
debug_assert!(state.producer_done);
// We need to join our helper thread, and it could be blocked in one
// of two locations. First is the wait for a request, but the
// initial drop of `HelperState` will take care of that. Otherwise
// it may be blocked in `client.acquire()`. We actually have no way
// of interrupting that, so resort to `pthread_kill` as a fallback.
// This signal should interrupt any blocking `read` call with
// `io::ErrorKind::Interrupt` and cause the thread to cleanly exit.
//
// Note that we don't do this forever though since there's a chance
// of bugs, so only do this opportunistically to make a best effort
// at clearing ourselves up.
for _ in 0..100 {
if state.consumer_done {
break;
}
unsafe {
// Ignore the return value here of `pthread_kill`,
// apparently on OSX if you kill a dead thread it will
// return an error, but on other platforms it may not. In
// that sense we don't actually know if this will succeed or
// not!
libc::pthread_kill(self.thread.as_pthread_t() as _, libc::SIGUSR1);
}
state = self
.state
.cvar
.wait_timeout(state, dur)
.unwrap_or_else(|e| e.into_inner())
.0;
thread::yield_now(); // we really want the other thread to run
}
// If we managed to actually see the consumer get done, then we can
// definitely wait for the thread. Otherwise it's... off in the ether
// I guess?
if state.consumer_done {
drop(self.thread.join());
}
}
}
unsafe fn fcntl_check(fd: c_int) -> Result<(), FromEnvErrorInner> {
match libc::fcntl(fd, libc::F_GETFD) {
-1 => Err(FromEnvErrorInner::CannotOpenFd(
fd,
io::Error::last_os_error(),
)),
_ => Ok(()),
}
}
unsafe fn fd_check(fd: c_int, check_pipe: bool) -> Result<(), FromEnvErrorInner> {
if check_pipe {
let mut stat = mem::zeroed();
if libc::fstat(fd, &mut stat) == -1 {
let last_os_error = io::Error::last_os_error();
fcntl_check(fd)?;
Err(FromEnvErrorInner::NotAPipe(fd, Some(last_os_error)))
} else {
// On android arm and i686 mode_t is u16 and st_mode is u32,
// this generates a type mismatch when S_IFIFO (declared as mode_t)
// is used in operations with st_mode, so we use this workaround
// to get the value of S_IFIFO with the same type of st_mode.
#[allow(unused_assignments)]
let mut s_ififo = stat.st_mode;
s_ififo = libc::S_IFIFO as _;
if stat.st_mode & s_ififo == s_ififo {
return Ok(());
}
Err(FromEnvErrorInner::NotAPipe(fd, None))
}
} else {
fcntl_check(fd)
}
}
fn clone_fd_and_set_cloexec(fd: c_int) -> Result<File, FromEnvErrorInner> {
// Safety: fd is a valid fd dand it remains open until returns
unsafe { BorrowedFd::borrow_raw(fd) }
.try_clone_to_owned()
.map(File::from)
.map_err(|err| FromEnvErrorInner::CannotOpenFd(fd, err))
}
fn set_cloexec(fd: c_int, set: bool) -> io::Result<()> {
unsafe {
let previous = cvt(libc::fcntl(fd, libc::F_GETFD))?;
let new = if set {
previous | libc::FD_CLOEXEC
} else {
previous & !libc::FD_CLOEXEC
};
if new != previous {
cvt(libc::fcntl(fd, libc::F_SETFD, new))?;
}
Ok(())
}
}
fn set_nonblocking(fd: c_int, set: bool) -> io::Result<()> {
let status_flag = if set { libc::O_NONBLOCK } else { 0 };
unsafe {
cvt(libc::fcntl(fd, libc::F_SETFL, status_flag))?;
}
Ok(())
}
fn cvt(t: c_int) -> io::Result<c_int> {
if t == -1 {
Err(io::Error::last_os_error())
} else {
Ok(t)
}
}
extern "C" fn sigusr1_handler(
_signum: c_int,
_info: *mut libc::siginfo_t,
_ptr: *mut libc::c_void,
) {
// nothing to do
}
#[cfg(test)]
mod test {
use super::Client as ClientImp;
use crate::{test::run_named_fifo_try_acquire_tests, Client};
use std::{
fs::File,
io::{self, Write},
os::unix::io::AsRawFd,
sync::Arc,
};
fn from_imp_client(imp: ClientImp) -> Client {
Client {
inner: Arc::new(imp),
}
}
fn new_client_from_fifo() -> (Client, String) {
let file = tempfile::NamedTempFile::new().unwrap();
let fifo_path = file.path().to_owned();
file.close().unwrap(); // Remove the NamedTempFile to create fifo
nix::unistd::mkfifo(&fifo_path, nix::sys::stat::Mode::S_IRWXU).unwrap();
let arg = format!("fifo:{}", fifo_path.to_str().unwrap());
(
ClientImp::from_fifo(&arg)
.unwrap()
.map(from_imp_client)
.unwrap(),
arg,
)
}
fn new_client_from_pipe() -> (Client, String) {
let (read, write) = nix::unistd::pipe().unwrap();
let read = File::from(read);
let mut write = File::from(write);
write.write_all(b"1").unwrap();
let arg = format!("{},{}", read.as_raw_fd(), write.as_raw_fd());
(
unsafe { ClientImp::from_pipe(&arg, true) }
.unwrap()
.map(from_imp_client)
.unwrap(),
arg,
)
}
#[test]
fn test_try_acquire_named_fifo() {
run_named_fifo_try_acquire_tests(&new_client_from_fifo().0);
}
#[test]
fn test_try_acquire_annoymous_pipe_linux_specific_optimization() {
#[cfg(not(target_os = "linux"))]
assert_eq!(
new_client_from_pipe().0.try_acquire().unwrap_err().kind(),
io::ErrorKind::Unsupported
);
#[cfg(target_os = "linux")]
{
let client = new_client_from_pipe().0;
client.acquire().unwrap().drop_without_releasing();
run_named_fifo_try_acquire_tests(&client);
}
}
#[test]
fn test_string_arg() {
let (client, arg) = new_client_from_fifo();
assert_eq!(client.inner.string_arg(), arg);
let (client, arg) = new_client_from_pipe();
assert_eq!(client.inner.string_arg(), arg);
}
}
