mirror of
https://github.com/fish-shell/fish-shell.git
synced 2024-12-26 12:13:46 +08:00
557 lines
20 KiB
Rust
557 lines
20 KiB
Rust
use std::os::unix::prelude::*;
|
|
use std::sync::atomic::{AtomicU64, Ordering};
|
|
use std::sync::{Arc, Mutex, Weak};
|
|
use std::time::{Duration, Instant};
|
|
|
|
use crate::common::exit_without_destructors;
|
|
use crate::fd_readable_set::FdReadableSet;
|
|
use crate::fds::AutoCloseFd;
|
|
use crate::flog::FLOG;
|
|
use crate::threads::assert_is_background_thread;
|
|
use crate::wutil::perror;
|
|
use errno::errno;
|
|
use libc::{c_void, EAGAIN, EINTR, EWOULDBLOCK};
|
|
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
use crate::fds::{make_autoclose_pipes, make_fd_nonblocking};
|
|
#[cfg(HAVE_EVENTFD)]
|
|
use libc::{EFD_CLOEXEC, EFD_NONBLOCK};
|
|
|
|
/// Reason for waking an item
|
|
#[derive(PartialEq, Eq)]
|
|
pub enum ItemWakeReason {
|
|
/// The fd became readable (or was HUP'd)
|
|
Readable,
|
|
/// The requested timeout was hit
|
|
Timeout,
|
|
/// The item was "poked" (woken up explicitly)
|
|
Poke,
|
|
}
|
|
|
|
/// An event signaller implemented using a file descriptor, so it can plug into
|
|
/// [`select()`](libc::select).
|
|
///
|
|
/// This is like a binary semaphore. A call to [`post()`](FdEventSignaller::post) will
|
|
/// signal an event, making the fd readable. Multiple calls to `post()` may be coalesced.
|
|
/// On Linux this uses [`eventfd()`](libc::eventfd), on other systems this uses a pipe.
|
|
/// [`try_consume()`](FdEventSignaller::try_consume) may be used to consume the event.
|
|
/// Importantly this is async signal safe. Of course it is `CLO_EXEC` as well.
|
|
pub struct FdEventSignaller {
|
|
// Always the read end of the fd; maybe the write end as well.
|
|
fd: OwnedFd,
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
write: OwnedFd,
|
|
}
|
|
|
|
impl FdEventSignaller {
|
|
/// The default constructor will abort on failure (fd exhaustion).
|
|
/// This should only be used during startup.
|
|
pub fn new() -> Self {
|
|
#[cfg(HAVE_EVENTFD)]
|
|
{
|
|
// Note we do not want to use EFD_SEMAPHORE because we are binary (not counting) semaphore.
|
|
let fd = unsafe { libc::eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK) };
|
|
if fd < 0 {
|
|
perror("eventfd");
|
|
exit_without_destructors(1);
|
|
}
|
|
Self {
|
|
fd: unsafe { OwnedFd::from_raw_fd(fd) },
|
|
}
|
|
}
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
{
|
|
// Implementation using pipes.
|
|
let Ok(pipes) = make_autoclose_pipes() else {
|
|
exit_without_destructors(1);
|
|
};
|
|
make_fd_nonblocking(pipes.read.as_raw_fd()).unwrap();
|
|
make_fd_nonblocking(pipes.write.as_raw_fd()).unwrap();
|
|
Self {
|
|
fd: pipes.read,
|
|
write: pipes.write,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// \return the fd to read from, for notification.
|
|
pub fn read_fd(&self) -> RawFd {
|
|
self.fd.as_raw_fd()
|
|
}
|
|
|
|
/// If an event is signalled, consume it; otherwise return.
|
|
/// This does not block.
|
|
/// This retries on EINTR.
|
|
pub fn try_consume(&self) -> bool {
|
|
// If we are using eventfd, we want to read a single uint64.
|
|
// If we are using pipes, read a lot; note this may leave data on the pipe if post has been
|
|
// called many more times. In no case do we care about the data which is read.
|
|
#[cfg(HAVE_EVENTFD)]
|
|
let mut buff = [0_u64; 1];
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
let mut buff = [0_u8; 1024];
|
|
let mut ret;
|
|
loop {
|
|
ret = unsafe {
|
|
libc::read(
|
|
self.read_fd(),
|
|
&mut buff as *mut _ as *mut c_void,
|
|
std::mem::size_of_val(&buff),
|
|
)
|
|
};
|
|
if ret >= 0 || errno().0 != EINTR {
|
|
break;
|
|
}
|
|
}
|
|
if ret < 0 && ![EAGAIN, EWOULDBLOCK].contains(&errno().0) {
|
|
perror("read");
|
|
}
|
|
ret > 0
|
|
}
|
|
|
|
/// Mark that an event has been received. This may be coalesced.
|
|
/// This retries on EINTR.
|
|
pub fn post(&self) {
|
|
// eventfd writes uint64; pipes write 1 byte.
|
|
#[cfg(HAVE_EVENTFD)]
|
|
let c = 1_u64;
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
let c = 1_u8;
|
|
let mut ret;
|
|
loop {
|
|
let bytes = c.to_ne_bytes();
|
|
ret = nix::unistd::write(self.write_fd(), &bytes);
|
|
|
|
match ret {
|
|
Ok(_) => break,
|
|
Err(nix::Error::EINTR) => continue,
|
|
Err(_) => break,
|
|
}
|
|
}
|
|
|
|
if let Err(err) = ret {
|
|
// EAGAIN occurs if either the pipe buffer is full or the eventfd overflows (very unlikely).
|
|
if ![nix::Error::EAGAIN, nix::Error::EWOULDBLOCK].contains(&err) {
|
|
perror("write");
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Perform a poll to see if an event is received.
|
|
/// If \p wait is set, wait until it is readable; this does not consume the event
|
|
/// but guarantees that the next call to wait() will not block.
|
|
/// \return true if readable, false if not readable, or not interrupted by a signal.
|
|
pub fn poll(&self, wait: bool /* = false */) -> bool {
|
|
let mut timeout = libc::timeval {
|
|
tv_sec: 0,
|
|
tv_usec: 0,
|
|
};
|
|
let mut fds: libc::fd_set = unsafe { std::mem::zeroed() };
|
|
unsafe { libc::FD_ZERO(&mut fds) };
|
|
unsafe { libc::FD_SET(self.read_fd(), &mut fds) };
|
|
let res = unsafe {
|
|
libc::select(
|
|
self.read_fd() + 1,
|
|
&mut fds,
|
|
std::ptr::null_mut(),
|
|
std::ptr::null_mut(),
|
|
if wait {
|
|
std::ptr::null_mut()
|
|
} else {
|
|
&mut timeout
|
|
},
|
|
)
|
|
};
|
|
res > 0
|
|
}
|
|
|
|
/// \return the fd to write to.
|
|
fn write_fd(&self) -> RawFd {
|
|
#[cfg(HAVE_EVENTFD)]
|
|
return self.fd.as_raw_fd();
|
|
#[cfg(not(HAVE_EVENTFD))]
|
|
return self.write.as_raw_fd();
|
|
}
|
|
}
|
|
|
|
/// Each item added to fd_monitor_t is assigned a unique ID, which is not recycled. Items may have
|
|
/// their callback triggered immediately by passing the ID. Zero is a sentinel.
|
|
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
|
|
pub struct FdMonitorItemId(u64);
|
|
|
|
impl From<FdMonitorItemId> for u64 {
|
|
fn from(value: FdMonitorItemId) -> Self {
|
|
value.0
|
|
}
|
|
}
|
|
|
|
impl From<u64> for FdMonitorItemId {
|
|
fn from(value: u64) -> Self {
|
|
FdMonitorItemId(value)
|
|
}
|
|
}
|
|
|
|
/// The callback type used by [`FdMonitorItem`]. It is passed a mutable reference to the
|
|
/// `FdMonitorItem`'s [`FdMonitorItem::fd`] and [the reason](ItemWakeupReason) for the wakeup.
|
|
/// It should return an [`ItemAction`] to indicate whether the item should be removed from the
|
|
/// [`FdMonitor`] set.
|
|
pub type Callback = Box<dyn Fn(&mut AutoCloseFd, ItemWakeReason) -> ItemAction + Send + Sync>;
|
|
|
|
/// An item containing an fd and callback, which can be monitored to watch when it becomes readable
|
|
/// and invoke the callback.
|
|
pub struct FdMonitorItem {
|
|
/// The fd to monitor
|
|
fd: AutoCloseFd,
|
|
/// A callback to be invoked when the fd is readable, or for another reason given by the wake reason.
|
|
/// If the fd is invalid on return from the function, then the item is removed from the [`FdMonitor`] set.
|
|
callback: Callback,
|
|
/// The timeout associated with waiting on this item or `None` to wait indefinitely. A timeout
|
|
/// of `0` is not supported.
|
|
timeout: Option<Duration>,
|
|
/// The last time we were called or the time of initialization.
|
|
last_time: Option<Instant>,
|
|
/// The id for this item, assigned by [`FdMonitor`].
|
|
item_id: FdMonitorItemId,
|
|
}
|
|
|
|
/// A value returned by the callback to indicate what to do with the item.
|
|
#[derive(PartialEq, Eq)]
|
|
pub enum ItemAction {
|
|
Remove,
|
|
Retain,
|
|
}
|
|
|
|
impl FdMonitorItem {
|
|
/// Returns the id for this `FdMonitorItem` that is registered with the [`FdMonitor`].
|
|
pub fn id(&self) -> FdMonitorItemId {
|
|
self.item_id
|
|
}
|
|
|
|
/// Return the duration until the timeout should trigger or `None`. A return of `0` means we are
|
|
/// at or past the timeout.
|
|
fn remaining_time(&self, now: &Instant) -> Option<Duration> {
|
|
let last_time = self.last_time.expect("Should always have a last_time!");
|
|
let timeout = self.timeout?;
|
|
assert!(now >= &last_time, "Steady clock went backwards or bug!");
|
|
let since = *now - last_time;
|
|
Some(if since >= timeout {
|
|
Duration::ZERO
|
|
} else {
|
|
timeout - since
|
|
})
|
|
}
|
|
|
|
/// Invoke this item's callback if its value (when its value is set in the fd or has timed out).
|
|
/// Returns `true` if the item should be retained or `false` if it should be removed from the
|
|
/// set.
|
|
fn service_item(&mut self, fds: &FdReadableSet, now: &Instant) -> ItemAction {
|
|
let mut result = ItemAction::Retain;
|
|
let readable = fds.test(self.fd.as_raw_fd());
|
|
let timed_out = !readable && self.remaining_time(now) == Some(Duration::ZERO);
|
|
if readable || timed_out {
|
|
self.last_time = Some(*now);
|
|
let reason = if readable {
|
|
ItemWakeReason::Readable
|
|
} else {
|
|
ItemWakeReason::Timeout
|
|
};
|
|
result = (self.callback)(&mut self.fd, reason);
|
|
}
|
|
result
|
|
}
|
|
|
|
/// Invoke this item's callback with a poke, if its id is present in the sorted poke list.
|
|
fn maybe_poke_item(&mut self, pokelist: &[FdMonitorItemId]) -> ItemAction {
|
|
if self.item_id.0 == 0 || pokelist.binary_search(&self.item_id).is_err() {
|
|
// Not pokeable or not in the poke list.
|
|
return ItemAction::Retain;
|
|
}
|
|
|
|
(self.callback)(&mut self.fd, ItemWakeReason::Poke)
|
|
}
|
|
|
|
pub fn new(fd: AutoCloseFd, timeout: Option<Duration>, callback: Callback) -> Self {
|
|
FdMonitorItem {
|
|
fd,
|
|
timeout,
|
|
callback,
|
|
item_id: FdMonitorItemId(0),
|
|
last_time: None,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// A thread-safe class which can monitor a set of fds, invoking a callback when any becomes
|
|
/// readable (or has been HUP'd) or when per-item-configurable timeouts are reached.
|
|
pub struct FdMonitor {
|
|
/// Our self-signaller. When this is written to, it means there are new items pending, new items
|
|
/// in the poke list, or terminate has been set.
|
|
change_signaller: Arc<FdEventSignaller>,
|
|
/// The data shared between the background thread and the `FdMonitor` instance.
|
|
data: Arc<Mutex<SharedData>>,
|
|
/// The last ID assigned or `0` if none.
|
|
last_id: AtomicU64,
|
|
}
|
|
|
|
// We don't want to manually implement `Sync` for `FdMonitor` but we do want to make sure that it's
|
|
// always using interior mutability correctly and therefore automatically `Sync`.
|
|
const _: () = {
|
|
// It is sufficient to declare the generic function pointers; calling them too would require
|
|
// using `const fn` with Send/Sync constraints which wasn't stabilized until rustc 1.61.0
|
|
fn assert_sync<T: Sync>() {}
|
|
let _ = assert_sync::<FdMonitor>;
|
|
};
|
|
|
|
/// Data shared between the `FdMonitor` instance and its associated `BackgroundFdMonitor`.
|
|
struct SharedData {
|
|
/// Pending items. This is set by the main thread with the mutex locked, then the background
|
|
/// thread grabs them.
|
|
pending: Vec<FdMonitorItem>,
|
|
/// List of IDs for items that need to be poked (explicitly woken up).
|
|
pokelist: Vec<FdMonitorItemId>,
|
|
/// Whether the background thread is running.
|
|
running: bool,
|
|
/// Used to signal that the background thread should terminate.
|
|
terminate: bool,
|
|
}
|
|
|
|
/// The background half of the fd monitor, running on its own thread.
|
|
struct BackgroundFdMonitor {
|
|
/// The list of items to monitor. This is only accessed from the background thread.
|
|
/// This doesn't need to be in any particular order.
|
|
items: Vec<FdMonitorItem>,
|
|
/// Our self-signaller. When this is written to, it means there are new items pending, new items
|
|
/// in the poke list, or terminate has been set.
|
|
change_signaller: Weak<FdEventSignaller>,
|
|
/// The data shared between the background thread and the `FdMonitor` instance.
|
|
data: Arc<Mutex<SharedData>>,
|
|
}
|
|
|
|
impl FdMonitor {
|
|
/// Add an item to the monitor. Returns the [`FdMonitorItemId`] assigned to the item.
|
|
pub fn add(&self, mut item: FdMonitorItem) -> FdMonitorItemId {
|
|
assert!(item.fd.is_valid());
|
|
assert!(item.timeout != Some(Duration::ZERO), "Invalid timeout!");
|
|
assert!(
|
|
item.item_id == FdMonitorItemId(0),
|
|
"Item should not already have an id!"
|
|
);
|
|
|
|
let item_id = self.last_id.fetch_add(1, Ordering::Relaxed) + 1;
|
|
let item_id = FdMonitorItemId(item_id);
|
|
let start_thread = {
|
|
// Lock around a local region
|
|
let mut data = self.data.lock().expect("Mutex poisoned!");
|
|
|
|
// Assign an id and add the item to pending
|
|
item.item_id = item_id;
|
|
data.pending.push(item);
|
|
|
|
// Start the thread if it hasn't already been started
|
|
let already_started = data.running;
|
|
data.running = true;
|
|
!already_started
|
|
};
|
|
|
|
if start_thread {
|
|
FLOG!(fd_monitor, "Thread starting");
|
|
let background_monitor = BackgroundFdMonitor {
|
|
data: Arc::clone(&self.data),
|
|
change_signaller: Arc::downgrade(&self.change_signaller),
|
|
items: Vec::new(),
|
|
};
|
|
crate::threads::spawn(move || {
|
|
background_monitor.run();
|
|
});
|
|
}
|
|
|
|
// Tickle our signaller.
|
|
self.change_signaller.post();
|
|
|
|
item_id
|
|
}
|
|
|
|
/// Mark that the item with the given ID needs to be woken up explicitly.
|
|
pub fn poke_item(&self, item_id: FdMonitorItemId) {
|
|
assert!(item_id.0 > 0, "Invalid item id!");
|
|
let needs_notification = {
|
|
let mut data = self.data.lock().expect("Mutex poisoned!");
|
|
let needs_notification = data.pokelist.is_empty();
|
|
// Insert it, sorted. But not if it already exists.
|
|
if let Err(pos) = data.pokelist.binary_search(&item_id) {
|
|
data.pokelist.insert(pos, item_id);
|
|
};
|
|
needs_notification
|
|
};
|
|
|
|
if needs_notification {
|
|
self.change_signaller.post();
|
|
}
|
|
}
|
|
|
|
pub fn new() -> Self {
|
|
Self {
|
|
data: Arc::new(Mutex::new(SharedData {
|
|
pending: Vec::new(),
|
|
pokelist: Vec::new(),
|
|
running: false,
|
|
terminate: false,
|
|
})),
|
|
change_signaller: Arc::new(FdEventSignaller::new()),
|
|
last_id: AtomicU64::new(0),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl BackgroundFdMonitor {
|
|
/// Starts monitoring the fd set and listening for new fds to add to the set. Takes ownership
|
|
/// over its instance so that this method cannot be called again.
|
|
fn run(mut self) {
|
|
assert_is_background_thread();
|
|
|
|
let mut pokelist: Vec<FdMonitorItemId> = Vec::new();
|
|
let mut fds = FdReadableSet::new();
|
|
|
|
loop {
|
|
// Poke any items that need it
|
|
if !pokelist.is_empty() {
|
|
self.poke(&pokelist);
|
|
pokelist.clear();
|
|
}
|
|
fds.clear();
|
|
|
|
// Our change_signaller is special-cased
|
|
let change_signal_fd = self.change_signaller.upgrade().unwrap().read_fd();
|
|
fds.add(change_signal_fd);
|
|
|
|
let mut now = Instant::now();
|
|
// Use Duration::MAX to represent no timeout for comparison purposes.
|
|
let mut timeout = Duration::MAX;
|
|
|
|
for item in &mut self.items {
|
|
fds.add(item.fd.as_raw_fd());
|
|
if item.last_time.is_none() {
|
|
item.last_time = Some(now);
|
|
}
|
|
timeout = timeout.min(item.timeout.unwrap_or(Duration::MAX));
|
|
}
|
|
|
|
// If we have no items, then we wish to allow the thread to exit, but after a time, so
|
|
// we aren't spinning up and tearing down the thread repeatedly. Set a timeout of 256
|
|
// msec; if nothing becomes readable by then we will exit. We refer to this as the
|
|
// wait-lap.
|
|
let is_wait_lap = self.items.is_empty();
|
|
if is_wait_lap {
|
|
assert!(
|
|
timeout == Duration::MAX,
|
|
"Should not have a timeout on wait lap!"
|
|
);
|
|
timeout = Duration::from_millis(256);
|
|
}
|
|
|
|
// Don't leave Duration::MAX as an actual timeout value
|
|
let timeout = match timeout {
|
|
Duration::MAX => None,
|
|
timeout => Some(timeout),
|
|
};
|
|
|
|
// Call select()
|
|
let ret = fds.check_readable(
|
|
timeout
|
|
.map(|duration| duration.as_micros() as u64)
|
|
.unwrap_or(FdReadableSet::kNoTimeout),
|
|
);
|
|
if ret < 0 && errno::errno().0 != libc::EINTR {
|
|
// Surprising error
|
|
perror("select");
|
|
}
|
|
|
|
// Update the value of `now` after waiting on `fds.check_readable()`; it's used in the
|
|
// servicer closure.
|
|
now = Instant::now();
|
|
|
|
// A predicate which services each item in turn, returning true if it should be removed
|
|
let servicer = |item: &mut FdMonitorItem| {
|
|
let fd = item.fd.as_raw_fd();
|
|
let action = item.service_item(&fds, &now);
|
|
if action == ItemAction::Remove {
|
|
FLOG!(fd_monitor, "Removing fd", fd);
|
|
}
|
|
action
|
|
};
|
|
|
|
// Service all items that are either readable or have timed out, and remove any which
|
|
// say to do so.
|
|
|
|
self.items
|
|
.retain_mut(|item| servicer(item) == ItemAction::Retain);
|
|
|
|
// Handle any changes if the change signaller was set. Alternatively, this may be the
|
|
// wait lap, in which case we might want to commit to exiting.
|
|
let change_signalled = fds.test(change_signal_fd);
|
|
if change_signalled || is_wait_lap {
|
|
// Clear the change signaller before processing incoming changes
|
|
self.change_signaller.upgrade().unwrap().try_consume();
|
|
let mut data = self.data.lock().expect("Mutex poisoned!");
|
|
|
|
// Move from `pending` to the end of `items`
|
|
self.items.extend(&mut data.pending.drain(..));
|
|
|
|
// Grab any poke list
|
|
assert!(
|
|
pokelist.is_empty(),
|
|
"poke list should be empty or else we're dropping pokes!"
|
|
);
|
|
std::mem::swap(&mut pokelist, &mut data.pokelist);
|
|
|
|
if data.terminate
|
|
|| (is_wait_lap
|
|
&& self.items.is_empty()
|
|
&& pokelist.is_empty()
|
|
&& !change_signalled)
|
|
{
|
|
// Maybe terminate is set. Alternatively, maybe we had no items, waited a bit,
|
|
// and still have no items. It's important to do this while holding the lock,
|
|
// otherwise we race with new items being added.
|
|
assert!(
|
|
data.running,
|
|
"Thread should be running because we're that thread"
|
|
);
|
|
FLOG!(fd_monitor, "Thread exiting");
|
|
data.running = false;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Poke items in the poke list, removing any items that close their fd in their callback. The
|
|
/// poke list is consumed after this. This is only called from the background thread.
|
|
fn poke(&mut self, pokelist: &[FdMonitorItemId]) {
|
|
self.items.retain_mut(|item| {
|
|
let action = item.maybe_poke_item(pokelist);
|
|
if action == ItemAction::Remove {
|
|
FLOG!(fd_monitor, "Removing fd", item.fd.as_raw_fd());
|
|
}
|
|
return action == ItemAction::Retain;
|
|
});
|
|
}
|
|
}
|
|
|
|
/// In ordinary usage, we never invoke the destructor. This is used in the tests to not leave stale
|
|
/// fds arounds; this is why it's very hacky!
|
|
impl Drop for FdMonitor {
|
|
fn drop(&mut self) {
|
|
// Safety: this is a port of the C++ code and we are running in the destructor. The C++ code
|
|
// had no way to bubble back any errors encountered here, and the pthread mutex the C++ code
|
|
// uses does not have a concept of mutex poisoning.
|
|
self.data.lock().expect("Mutex poisoned!").terminate = true;
|
|
self.change_signaller.post();
|
|
|
|
// Safety: see note above.
|
|
while self.data.lock().expect("Mutex poisoned!").running {
|
|
std::thread::sleep(Duration::from_millis(5));
|
|
}
|
|
}
|
|
}
|