feat(select): fd arms in select + timed fd waits (RFC 008 phase 1)
FdArm composes fd readiness with channel arms on one wait epoch. Selectable grows fallible sel_register and an eager-cleanup hook; losing/stop-unwound/timed-out fd arms are unregistered (waiters entry + kernel ONESHOT) so the fd is never poisoned. try_select / try_select_timeout surface registration errors (EBADF, EMFILE, AlreadyExists) instead of RFC 008's permanently-ready lean, which would busy-loop a healthy-but-unregistrable fd; select/select_timeout stay infallible for channel-only arms. Adds wait_readable_timeout / wait_writable_timeout as one-arm selects. Known benign race (pre-existing, slightly widened): a queued FdReady racing the cleanup DEL can spuriously wake a fresh waiter on that fd; absorbed by select's defensive re-loop. Fixable by epoch-stamping completions.
This commit is contained in:
Claude
+153
-26
@@ -361,7 +361,7 @@ impl<T: Send + 'static> crate::timer::TimerTarget for RawMutex<Inner<T>> {
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// select — ready-index wait over multiple receivers
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// ---------------------------------------------------------------------------
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mod sealed {
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pub(crate) mod sealed {
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pub trait Sealed {}
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}
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impl<T> sealed::Sealed for Receiver<T> {}
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@@ -371,28 +371,46 @@ impl<T> sealed::Sealed for Receiver<T> {}
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///
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/// Contract (all under the arm's own lock): `sel_register` checks-or-
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/// registers atomically — if the arm is ready it does NOT register and
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/// returns `false`; otherwise it publishes `(pid, epoch)` where its wakers
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/// will find it. "Ready" means a receive would not park: a message is
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/// queued, or the arm is closed.
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/// returns `Ok(false)`; otherwise it publishes `(pid, epoch)` where its
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/// wakers will find it and returns `Ok(true)`. "Ready" means a receive
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/// would not park: a message is queued, or the arm is closed. `Err` means
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/// the arm could not register at all (only fd arms can fail; channel
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/// registration is infallible) — the wait must be retired and earlier
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/// eager-cleanup arms unregistered.
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pub trait Selectable: sealed::Sealed {
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#[doc(hidden)]
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fn sel_register(&self, pid: Pid, epoch: u32) -> bool;
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fn sel_register(&self, pid: Pid, epoch: u32) -> std::io::Result<bool>;
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#[doc(hidden)]
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fn sel_ready(&self) -> bool;
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/// Remove this arm's `(pid, epoch)` registration if — and only if — it
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/// is still in place. Default no-op: a losing channel arm's stale
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/// registration is inert (its wakers die at the epoch CAS; the next
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/// wait overwrites the slot). Fd arms override this: their staleness
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/// poisons the fd (waiters entry + kernel-side ONESHOT registration)
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/// and needs an eager cleanup pass.
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#[doc(hidden)]
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fn sel_unregister(&self, _pid: Pid, _epoch: u32) {}
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/// Whether this arm requires the eager cleanup pass at all. Gates the
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/// post-wake `sel_unregister` sweep so channel-only selects keep
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/// today's zero-cancellation hot path.
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#[doc(hidden)]
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fn sel_eager_cleanup(&self) -> bool {
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false
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}
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}
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impl<T> Selectable for Receiver<T> {
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fn sel_register(&self, pid: Pid, epoch: u32) -> bool {
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fn sel_register(&self, pid: Pid, epoch: u32) -> std::io::Result<bool> {
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let mut g = self.inner.lock();
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if !g.queue.is_empty() || g.senders == 0 {
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return false;
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return Ok(false);
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}
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debug_assert!(
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g.parked_receiver.is_none_or(|(p, _)| p == pid),
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"channel has more than one receiver"
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);
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g.parked_receiver = Some((pid, epoch));
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true
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Ok(true)
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}
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fn sel_ready(&self) -> bool {
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@@ -429,30 +447,95 @@ impl<T> Selectable for Receiver<T> {
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/// self-clean at their wakers' failed CAS, or get overwritten by this
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/// receiver's next wait on that channel.
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///
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/// Panics if `arms` is empty, or when called outside an actor.
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/// Panics if `arms` is empty, when called outside an actor, or if an fd
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/// arm fails to register (EBADF, EMFILE, a second waiter on one fd —
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/// see [`try_select`] for the fallible form; channel-only selects cannot
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/// fail).
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pub fn select(arms: &[&dyn Selectable]) -> usize {
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try_select(arms).expect("select(): fd arm failed to register (use try_select)")
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}
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/// [`select`], fallible: `Err` when an arm fails to register (only fd
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/// arms can — EBADF, EMFILE on the epoll set, or a second waiter on an
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/// fd that already has one). On `Err` the wait is fully retired and no
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/// registration is left behind: every arm registered before the failing
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/// one has been unregistered.
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pub fn try_select(arms: &[&dyn Selectable]) -> std::io::Result<usize> {
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assert!(!arms.is_empty(), "select() on an empty arm list");
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let me = crate::actor::current_pid().expect("select() called outside an actor");
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loop {
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let epoch = crate::scheduler::begin_wait();
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if let Some(i) = register_arms(me, epoch, arms) {
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return i;
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if let Some(i) = register_arms(me, epoch, arms)? {
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return Ok(i);
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}
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// Stale fd registrations are not harmless (a losing fd arm's
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// waiters entry poisons the fd with AlreadyExists and its
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// kernel-side ONESHOT registration can fire arbitrarily late), so
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// selects containing fd arms run an eager cleanup pass after the
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// park — including when a terminal stop unwinds out of it, via
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// the guard. Channel-only selects skip all of it: `eager` is
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// false, the guard is disarmed, and the loser-arm self-cleaning
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// story is unchanged.
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let eager = arms.iter().any(|a| a.sel_eager_cleanup());
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let mut guard = UnregisterGuard { arms, me, epoch, armed: eager };
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crate::scheduler::park_current();
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if eager {
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unregister_arms(arms, me, epoch);
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}
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guard.armed = false;
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drop(guard);
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// Woken precisely: an arm's send (message) or last-sender drop
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// (closure) consumed our epoch, and both leave their arm ready —
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// return the first one, in priority order (which may be a
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// different, higher-priority arm than the one that woke us; its
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// message stays queued and re-reports ready on the next call).
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// Fd arms classify by a fresh zero-timeout poll, so they too are
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// a pure function of state — independent of the registration the
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// cleanup pass just removed.
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for (i, arm) in arms.iter().enumerate() {
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if arm.sel_ready() {
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return i;
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return Ok(i);
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}
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}
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// Unreachable by protocol (a stop wake unwinds out of
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// park_current). Defensive: re-open the wait and re-register —
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// stale own-registrations are overwritten.
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// stale own-registrations are overwritten (channels) or were
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// removed by the cleanup pass above (fds).
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}
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}
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/// Eager-cleanup sweep: remove every fd arm's registration that is still
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/// ours. No-op per channel arm (one virtual call); one io-lock visit per
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/// fd arm.
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fn unregister_arms(arms: &[&dyn Selectable], me: Pid, epoch: u32) {
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for arm in arms {
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if arm.sel_eager_cleanup() {
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arm.sel_unregister(me, epoch);
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}
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}
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}
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/// Stop-unwind twin of the explicit cleanup pass: a terminal stop unwinds
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/// out of `park_current`, and a registered fd arm must not outlive its
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/// actor (the generalization of `wait_fd`'s `Dereg`). Disarmed on the
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/// normal path after the explicit pass runs; never armed when no fd arm
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/// registered, keeping the channel-only path guard-free in effect.
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struct UnregisterGuard<'a> {
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arms: &'a [&'a dyn Selectable],
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me: Pid,
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epoch: u32,
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armed: bool,
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}
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impl Drop for UnregisterGuard<'_> {
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fn drop(&mut self) {
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if self.armed {
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unregister_arms(self.arms, self.me, self.epoch);
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}
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}
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}
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@@ -462,19 +545,35 @@ pub fn select(arms: &[&dyn Selectable]) -> usize {
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/// right after its registration wakes the caller through the protocol (the
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/// prep-to-park window is closed by RunningNotified).
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///
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/// `Some(i)` = arm `i` was ready, the pass stopped, and the wait has been
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/// RETIRED (no park may follow): earlier arms hold live-epoch
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/// registrations, so the epoch is bumped, a landed notification eaten, and
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/// a pending stop re-observed — without which a stale arm wake could fault
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/// a later one-shot park. `None` = every arm registered; the caller parks.
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fn register_arms(me: Pid, epoch: u32, arms: &[&dyn Selectable]) -> Option<usize> {
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/// `Ok(Some(i))` = arm `i` was ready, the pass stopped, and the wait has
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/// been RETIRED (no park may follow): earlier arms hold live-epoch
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/// registrations, so earlier *fd* arms are unregistered eagerly, then the
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/// epoch is bumped, a landed notification eaten, and a pending stop
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/// re-observed — without which a stale arm wake could fault a later
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/// one-shot park. `Err` = an arm failed to register; identical unwind
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/// (earlier fd arms unregistered, wait retired). `Ok(None)` = every arm
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/// registered; the caller parks.
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fn register_arms(
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me: Pid,
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epoch: u32,
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arms: &[&dyn Selectable],
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) -> std::io::Result<Option<usize>> {
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for (i, arm) in arms.iter().enumerate() {
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if !arm.sel_register(me, epoch) {
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let registered = match arm.sel_register(me, epoch) {
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Ok(r) => r,
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Err(e) => {
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unregister_arms(&arms[..i], me, epoch);
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crate::scheduler::retire_wait();
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return Some(i);
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return Err(e);
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}
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};
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if !registered {
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unregister_arms(&arms[..i], me, epoch);
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crate::scheduler::retire_wait();
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return Ok(Some(i));
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}
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}
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None
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Ok(None)
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}
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/// The [`select_timeout`] timer target: stateless, because precise wakes
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@@ -506,16 +605,29 @@ impl crate::timer::TimerTarget for SelectTimeout {
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/// `Duration::ZERO` is a valid timeout: it parks until the immediately-due
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/// timer is drained, then reports `None` unless an arm was already ready.
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///
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/// Panics if `arms` is empty, or when called outside an actor.
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/// Panics if `arms` is empty, when called outside an actor, or if an fd
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/// arm fails to register (see [`try_select_timeout`] for the fallible
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/// form; channel-only selects cannot fail).
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pub fn select_timeout(
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arms: &[&dyn Selectable],
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timeout: std::time::Duration,
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) -> Option<usize> {
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try_select_timeout(arms, timeout)
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.expect("select_timeout(): fd arm failed to register (use try_select_timeout)")
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}
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/// [`select_timeout`], fallible: `Err` when an arm fails to register
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/// (only fd arms can). On `Err` the wait is fully retired and no
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/// registration — arm-side or kernel-side — is left behind.
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pub fn try_select_timeout(
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arms: &[&dyn Selectable],
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timeout: std::time::Duration,
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) -> std::io::Result<Option<usize>> {
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assert!(!arms.is_empty(), "select_timeout() on an empty arm list");
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let me = crate::actor::current_pid().expect("select_timeout() called outside an actor");
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let epoch = crate::scheduler::begin_wait();
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if let Some(i) = register_arms(me, epoch, arms) {
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return Some(i); // ready now: the timer was never armed
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if let Some(i) = register_arms(me, epoch, arms)? {
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return Ok(Some(i)); // ready now: the timer was never armed
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}
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// Arm the timer after the registration pass, outside every Channel
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@@ -524,7 +636,22 @@ pub fn select_timeout(
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let target: std::sync::Arc<dyn crate::timer::TimerTarget> = std::sync::Arc::new(SelectTimeout);
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crate::scheduler::insert_wait_timer(deadline, me, target, epoch);
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// Same eager-cleanup story as `try_select`: the timer arm needs none
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// (stateless, stale entries die at the epoch CAS), channel arms need
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// none, fd arms do — and a timer win in particular leaves every fd
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// arm's registration behind, which without this pass would poison
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// those fds until a kernel event happened to fire.
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let eager = arms.iter().any(|a| a.sel_eager_cleanup());
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let mut guard = UnregisterGuard { arms, me, epoch, armed: eager };
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crate::scheduler::park_current();
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if eager {
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unregister_arms(arms, me, epoch);
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}
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guard.armed = false;
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drop(guard);
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// Woken precisely: an arm (ready below) or the timer (nothing ready).
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arms.iter().position(|arm| arm.sel_ready())
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Ok(arms.iter().position(|arm| arm.sel_ready()))
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}
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+6
-2
@@ -45,7 +45,10 @@ static ALLOCATOR: preempt::PreemptingAllocator = preempt::PreemptingAllocator;
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// Public API re-exports
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// ---------------------------------------------------------------------------
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pub use channel::{channel, select, select_timeout, Receiver, RecvError, RecvTimeoutError, Selectable, Sender};
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pub use channel::{
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channel, select, select_timeout, try_select, try_select_timeout, Receiver, RecvError,
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RecvTimeoutError, Selectable, Sender,
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};
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pub use gen_server::{CallError, CallTimeoutError, CastError, GenServer, ServerBuilder, ServerCtx, ServerRef, Watcher};
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pub use link::{link, trap_exit, unlink, ExitSignal};
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pub use monitor::{demonitor, monitor, Down, DownReason, Monitor, MonitorId};
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@@ -55,7 +58,8 @@ pub use registry::{name_of, register, unregister, whereis, RegisterError};
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pub use runtime::{init, Config, Runtime};
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pub use scheduler::{
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block_on_io, request_stop, run, self_pid, sleep, spawn, spawn_under, wait_readable,
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wait_writable, yield_now, JoinError, JoinHandle,
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wait_readable_timeout, wait_writable, wait_writable_timeout, yield_now, FdArm, JoinError,
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JoinHandle,
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};
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pub use supervisor::{ChildSpec, OneForOne, Restart, Signal, Strategy};
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@@ -432,6 +432,138 @@ fn wait_fd(fd: std::os::fd::RawFd, readable: bool, writable: bool) -> std::io::R
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Ok(())
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}
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// ---------------------------------------------------------------------------
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// FdArm — fd readiness as a select arm (RFC 008)
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// ---------------------------------------------------------------------------
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/// An fd-readiness arm for [`crate::select`] / [`crate::select_timeout`]:
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/// ready when the fd is readable (resp. writable), composable with channel
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/// receivers on one wait epoch. Phase-1 rules apply: one waiter per fd at a
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/// time, one direction per arm (duplex on a single fd needs `dup`; epoll
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/// registrations key on the open file description, so dup'd fds register
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/// independently).
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pub struct FdArm {
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fd: std::os::fd::RawFd,
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readable: bool,
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writable: bool,
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}
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impl FdArm {
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pub fn readable(fd: std::os::fd::RawFd) -> Self {
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FdArm { fd, readable: true, writable: false }
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}
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pub fn writable(fd: std::os::fd::RawFd) -> Self {
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FdArm { fd, readable: false, writable: true }
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}
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}
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impl crate::channel::sealed::Sealed for FdArm {}
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impl crate::channel::Selectable for FdArm {
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/// Ready-now check is a zero-timeout `poll(2)`; if the requested events
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/// are pending the wait is retired without registering (`Ok(false)`,
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/// the channel-arm contract). Otherwise register with the io thread —
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/// every failure surfaces as `Err` (EBADF including a closed-fd
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/// POLLNVAL, EMFILE on the epoll set, AlreadyExists for a second
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/// waiter on the fd): the fallible-out, nothing-left-behind rule, in
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/// deviation from RFC 008's permanently-ready lean, which would spin a
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/// consumer whose fd is healthy but unregistrable (EMFILE).
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fn sel_register(&self, pid: Pid, epoch: u32) -> std::io::Result<bool> {
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if poll_events(self.fd, self.readable, self.writable)? {
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return Ok(false);
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}
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with_runtime(|inner| {
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let mut io = inner.io.lock().unwrap();
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io.as_mut()
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.expect("io thread not started")
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.epoll_register(self.fd, pid, epoch, self.readable, self.writable)
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})?;
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Ok(true)
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}
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/// Classification is the same zero-timeout poll: a pure function of fd
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/// state, independent of the registration the cleanup pass removed. An
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/// error here (EBADF: fd closed mid-wait) reports READY — the
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/// consumer's read/write surfaces the errno; a dead arm is an event,
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/// not a hang.
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fn sel_ready(&self) -> bool {
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poll_events(self.fd, self.readable, self.writable).unwrap_or(true)
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}
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/// `wait_fd`'s `Dereg` compare, verbatim: remove the waiters entry and
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/// kernel-side registration iff the entry is still `(pid, epoch)`-ours.
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/// A `FdReady` racing the wake may have consumed it (it removes + DELs
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/// under the io lock), after which the fd may even carry ANOTHER
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/// actor's fresh registration; in that case touch nothing.
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fn sel_unregister(&self, pid: Pid, epoch: u32) {
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with_runtime(|inner| {
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let mut io = inner.io.lock().unwrap();
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if let Some(io) = io.as_mut() {
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if io.waiters.get(&self.fd) == Some(&(pid, epoch)) {
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io.waiters.remove(&self.fd);
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io.epoll_deregister(self.fd);
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}
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}
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});
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}
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fn sel_eager_cleanup(&self) -> bool {
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true
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}
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}
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/// Zero-timeout `poll(2)`: are any of the requested events (or ERR/HUP,
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/// which make the consumer's read/write fail loudly rather than park
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/// forever) pending on `fd`? POLLNVAL maps to `Err(EBADF)`.
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fn poll_events(fd: std::os::fd::RawFd, readable: bool, writable: bool) -> std::io::Result<bool> {
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let mut events: libc::c_short = 0;
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if readable {
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events |= libc::POLLIN;
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}
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if writable {
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events |= libc::POLLOUT;
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}
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let mut pfd = libc::pollfd { fd, events, revents: 0 };
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loop {
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let r = unsafe { libc::poll(&mut pfd, 1, 0) };
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if r < 0 {
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let e = std::io::Error::last_os_error();
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if e.kind() == std::io::ErrorKind::Interrupted {
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continue;
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}
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return Err(e);
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}
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if r == 0 {
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return Ok(false);
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}
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if pfd.revents & libc::POLLNVAL != 0 {
|
||||
return Err(std::io::Error::from_raw_os_error(libc::EBADF));
|
||||
}
|
||||
return Ok(pfd.revents & (events | libc::POLLERR | libc::POLLHUP) != 0);
|
||||
}
|
||||
}
|
||||
|
||||
/// Wait until `fd` is readable or `timeout` elapses: `Ok(true)` = ready,
|
||||
/// `Ok(false)` = timed out. A one-arm [`crate::try_select_timeout`].
|
||||
pub fn wait_readable_timeout(
|
||||
fd: std::os::fd::RawFd,
|
||||
timeout: std::time::Duration,
|
||||
) -> std::io::Result<bool> {
|
||||
let arm = FdArm::readable(fd);
|
||||
Ok(crate::channel::try_select_timeout(&[&arm], timeout)?.is_some())
|
||||
}
|
||||
|
||||
/// Wait until `fd` is writable or `timeout` elapses: `Ok(true)` = ready,
|
||||
/// `Ok(false)` = timed out.
|
||||
pub fn wait_writable_timeout(
|
||||
fd: std::os::fd::RawFd,
|
||||
timeout: std::time::Duration,
|
||||
) -> std::io::Result<bool> {
|
||||
let arm = FdArm::writable(fd);
|
||||
Ok(crate::channel::try_select_timeout(&[&arm], timeout)?.is_some())
|
||||
}
|
||||
|
||||
pub fn read(fd: std::os::fd::RawFd, buf: &mut [u8]) -> std::io::Result<usize> {
|
||||
wait_readable(fd)?;
|
||||
let n = unsafe { libc::read(fd, buf.as_mut_ptr() as *mut _, buf.len()) };
|
||||
|
||||
@@ -0,0 +1,403 @@
|
||||
//! RFC 008 — fd arms in select. Beyond the functional cases, the
|
||||
//! *_stays_usable tests are the soundness probes for the one asymmetry the
|
||||
//! RFC must close: a losing CHANNEL arm's stale registration is inert, but
|
||||
//! a losing FD arm's registration (waiters entry + kernel ONESHOT) poisons
|
||||
//! the fd with AlreadyExists until the eager cleanup pass removes it. Every
|
||||
//! "loser" scenario therefore re-waits on the same fd afterwards and must
|
||||
//! succeed — pre-cleanup, each of those re-waits errors or hangs.
|
||||
//!
|
||||
//! House pattern: actor panics are trampoline-caught and `run` returns
|
||||
//! normally, so every test funnels its result into an outcome flag asserted
|
||||
//! OUTSIDE `run` — an in-actor assertion alone passes vacuously.
|
||||
|
||||
use smarm::{
|
||||
channel, run, select, select_timeout, spawn, try_select, wait_readable,
|
||||
wait_readable_timeout, wait_writable_timeout, yield_now, FdArm,
|
||||
};
|
||||
use std::os::fd::RawFd;
|
||||
use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
|
||||
use std::sync::Arc;
|
||||
use std::time::{Duration, Instant};
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Pipe helper (as in io_epoll.rs)
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
struct Pipe {
|
||||
read: RawFd,
|
||||
write: RawFd,
|
||||
}
|
||||
|
||||
impl Pipe {
|
||||
fn new() -> Self {
|
||||
let mut fds: [libc::c_int; 2] = [0; 2];
|
||||
let r = unsafe { libc::pipe2(fds.as_mut_ptr(), libc::O_CLOEXEC | libc::O_NONBLOCK) };
|
||||
assert_eq!(r, 0, "pipe2 failed");
|
||||
Pipe { read: fds[0], write: fds[1] }
|
||||
}
|
||||
}
|
||||
|
||||
impl Drop for Pipe {
|
||||
fn drop(&mut self) {
|
||||
unsafe {
|
||||
libc::close(self.read);
|
||||
libc::close(self.write);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn raw_write(fd: RawFd, buf: &[u8]) -> isize {
|
||||
unsafe { libc::write(fd, buf.as_ptr() as *const _, buf.len()) }
|
||||
}
|
||||
|
||||
fn raw_read(fd: RawFd, buf: &mut [u8]) -> isize {
|
||||
unsafe { libc::read(fd, buf.as_mut_ptr() as *mut _, buf.len()) }
|
||||
}
|
||||
|
||||
fn flag() -> (Arc<AtomicBool>, Arc<AtomicBool>) {
|
||||
let f = Arc::new(AtomicBool::new(false));
|
||||
(f.clone(), f)
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Ready-now: data already pending retires the wait without parking.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn fd_arm_ready_now_returns_without_parking() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
assert_eq!(raw_write(p.write, b"x"), 1);
|
||||
let (_tx, rx) = channel::<i64>();
|
||||
let fd_arm = FdArm::readable(p.read);
|
||||
// fd arm at index 1: the ready-now path must also work for a
|
||||
// non-first arm (and clean nothing — channel arms are inert).
|
||||
let i = select(&[&rx, &fd_arm]);
|
||||
assert_eq!(i, 1);
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(p.read, &mut buf), 1);
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Park-then-wake: fd arm wins against an idle channel arm.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn fd_arm_parks_until_data_then_wins() {
|
||||
let got = Arc::new(AtomicU32::new(0));
|
||||
let got2 = got.clone();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
let (_tx_keepalive, rx) = channel::<i64>();
|
||||
|
||||
let h = spawn(move || {
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
let i = select(&[&fd_arm, &rx]);
|
||||
assert_eq!(i, 0);
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
got2.store(buf[0] as u32, Ordering::SeqCst);
|
||||
});
|
||||
yield_now(); // let it park
|
||||
assert_eq!(raw_write(wfd, b"y"), 1);
|
||||
let _ = h.join();
|
||||
});
|
||||
assert_eq!(got.load(Ordering::SeqCst), b'y' as u32);
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// THE asymmetry probe: channel arm wins, losing fd arm must be cleaned —
|
||||
// the same actor (and the io thread) must be able to wait that fd again.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn losing_fd_arm_is_cleaned_up_and_fd_stays_usable() {
|
||||
let got = Arc::new(AtomicU32::new(0));
|
||||
let got2 = got.clone();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
let (tx, rx) = channel::<i64>();
|
||||
|
||||
let h = spawn(move || {
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
// Channel wins; the fd arm registered and lost.
|
||||
let i = select(&[&fd_arm, &rx]);
|
||||
assert_eq!(i, 1);
|
||||
assert_eq!(rx.try_recv().unwrap(), Some(7));
|
||||
|
||||
// Pre-cleanup this wait_readable fails AlreadyExists (the
|
||||
// waiters entry is stale-ours) — the cleanup pass must have
|
||||
// removed it.
|
||||
wait_readable(rfd).unwrap();
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
got2.store(buf[0] as u32, Ordering::SeqCst);
|
||||
});
|
||||
yield_now(); // let it park in the select
|
||||
tx.send(7).unwrap();
|
||||
yield_now(); // let it reach the second wait
|
||||
assert_eq!(raw_write(wfd, b"z"), 1);
|
||||
let _ = h.join();
|
||||
});
|
||||
assert_eq!(got.load(Ordering::SeqCst), b'z' as u32);
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Ready-now on a LATER arm must unregister an earlier fd arm (the
|
||||
// register_arms prefix-cleanup path: no park ever happens).
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn ready_now_later_arm_cleans_earlier_fd_arm() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
let (tx, rx) = channel::<i64>();
|
||||
tx.send(1).unwrap(); // arm 1 ready before the select
|
||||
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
let i = select(&[&fd_arm, &rx]);
|
||||
assert_eq!(i, 1);
|
||||
assert_eq!(rx.try_recv().unwrap(), Some(1));
|
||||
|
||||
// The fd arm registered (idle pipe), then arm 1 retired the wait.
|
||||
// Its registration must have been removed in the same pass.
|
||||
assert_eq!(raw_write(wfd, b"a"), 1);
|
||||
wait_readable(rfd).unwrap();
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Two fd arms in one select (phase-1: distinct fds, nothing special).
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn two_fd_arms_second_fires_first_stays_usable() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let pa = Pipe::new();
|
||||
let pb = Pipe::new();
|
||||
let (rfd_a, wfd_a) = (pa.read, pa.write);
|
||||
let (rfd_b, wfd_b) = (pb.read, pb.write);
|
||||
|
||||
let h = spawn(move || {
|
||||
let a = FdArm::readable(rfd_a);
|
||||
let b = FdArm::readable(rfd_b);
|
||||
let i = select(&[&a, &b]);
|
||||
assert_eq!(i, 1);
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd_b, &mut buf), 1);
|
||||
|
||||
// Arm a lost; its fd must be immediately re-waitable.
|
||||
assert_eq!(raw_write(wfd_a, b"q"), 1);
|
||||
wait_readable(rfd_a).unwrap();
|
||||
assert_eq!(raw_read(rfd_a, &mut buf), 1);
|
||||
assert_eq!(buf[0], b'q');
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
yield_now();
|
||||
assert_eq!(raw_write(wfd_b, b"b"), 1);
|
||||
let _ = h.join();
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// select_timeout: timer wins over an idle fd arm; the fd is left clean.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn select_timeout_timer_beats_idle_fd_arm_and_fd_stays_usable() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
let start = Instant::now();
|
||||
let r = select_timeout(&[&fd_arm], Duration::from_millis(30));
|
||||
assert!(r.is_none(), "idle fd must time out");
|
||||
assert!(start.elapsed() >= Duration::from_millis(30));
|
||||
|
||||
// Timer win is exactly the case where the fd arm's registration is
|
||||
// left behind without an eager pass.
|
||||
assert_eq!(raw_write(wfd, b"c"), 1);
|
||||
wait_readable(rfd).unwrap();
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Derived wrappers.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn wait_readable_timeout_times_out_then_succeeds_with_data() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
|
||||
let start = Instant::now();
|
||||
assert_eq!(wait_readable_timeout(rfd, Duration::from_millis(30)).unwrap(), false);
|
||||
assert!(start.elapsed() >= Duration::from_millis(30));
|
||||
|
||||
// Timed-out wait must leave the fd clean; ready path returns true.
|
||||
assert_eq!(raw_write(wfd, b"d"), 1);
|
||||
assert_eq!(wait_readable_timeout(rfd, Duration::from_secs(5)).unwrap(), true);
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn wait_readable_timeout_wakes_on_late_data() {
|
||||
let got = Arc::new(AtomicU32::new(0));
|
||||
let got2 = got.clone();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
let h = spawn(move || {
|
||||
assert_eq!(wait_readable_timeout(rfd, Duration::from_secs(5)).unwrap(), true);
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
got2.store(buf[0] as u32, Ordering::SeqCst);
|
||||
});
|
||||
yield_now();
|
||||
assert_eq!(raw_write(wfd, b"e"), 1);
|
||||
let _ = h.join();
|
||||
});
|
||||
assert_eq!(got.load(Ordering::SeqCst), b'e' as u32);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn wait_writable_timeout_ready_now_on_empty_pipe() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
// An empty pipe's write end is writable: ready-now path, no park.
|
||||
assert_eq!(wait_writable_timeout(p.write, Duration::from_secs(5)).unwrap(), true);
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Error surface: registration failure is an Err from try_select, with the
|
||||
// wait retired (the actor can immediately wait on something else).
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn try_select_surfaces_registration_error_and_retires_the_wait() {
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let bad: RawFd = {
|
||||
let p = Pipe::new();
|
||||
p.read
|
||||
}; // both ends closed by Drop: EBADF on registration
|
||||
|
||||
let fd_arm = FdArm::readable(bad);
|
||||
let err = try_select(&[&fd_arm]).unwrap_err();
|
||||
// EBADF, whether the pre-poll or epoll_ctl ADD reports it.
|
||||
assert_eq!(err.raw_os_error(), Some(libc::EBADF));
|
||||
|
||||
// The wait was retired: a normal select right after works.
|
||||
let (tx, rx) = channel::<i64>();
|
||||
tx.send(9).unwrap();
|
||||
let i = select(&[&rx]);
|
||||
assert_eq!(i, 0);
|
||||
assert_eq!(rx.try_recv().unwrap(), Some(9));
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Stop-unwind: an actor stopped while parked in an fd-arm select must not
|
||||
// poison the fd (the UnregisterGuard generalization of wait_fd's Dereg).
|
||||
// Mirrors io_epoll.rs::stopped_waiter_does_not_poison_the_fd.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn stopped_selector_does_not_poison_the_fd() {
|
||||
let seen = Arc::new(AtomicU32::new(0));
|
||||
let seen_outer = seen.clone();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
let (_tx_keepalive, rx) = channel::<i64>();
|
||||
|
||||
let h = spawn(move || {
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
select(&[&fd_arm, &rx]);
|
||||
unreachable!("neither arm ever fires while this actor lives");
|
||||
});
|
||||
yield_now(); // let it reach the park
|
||||
smarm::request_stop(h.pid());
|
||||
let _ = h.join(); // Ok(()): stopped, not panicked
|
||||
|
||||
// Second waiter on the SAME fd must register and be woken.
|
||||
let seen2 = seen.clone();
|
||||
let h2 = spawn(move || {
|
||||
wait_readable(rfd).unwrap();
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
seen2.store(buf[0] as u32, Ordering::SeqCst);
|
||||
});
|
||||
yield_now();
|
||||
assert_eq!(raw_write(wfd, b"x"), 1);
|
||||
let _ = h2.join();
|
||||
});
|
||||
assert_eq!(seen_outer.load(Ordering::SeqCst), b'x' as u32);
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Phase-1 misuse: a second waiter on an fd that already has one is an Err
|
||||
// (AlreadyExists), not a hang — and does not disturb the first waiter.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
#[test]
|
||||
fn second_waiter_on_same_fd_errs_without_disturbing_the_first() {
|
||||
let got = Arc::new(AtomicU32::new(0));
|
||||
let got2 = got.clone();
|
||||
let (ok, ok2) = flag();
|
||||
run(move || {
|
||||
let p = Pipe::new();
|
||||
let (rfd, wfd) = (p.read, p.write);
|
||||
|
||||
let h = spawn(move || {
|
||||
wait_readable(rfd).unwrap();
|
||||
let mut buf = [0u8; 1];
|
||||
assert_eq!(raw_read(rfd, &mut buf), 1);
|
||||
got2.store(buf[0] as u32, Ordering::SeqCst);
|
||||
});
|
||||
yield_now(); // first waiter parked
|
||||
|
||||
let fd_arm = FdArm::readable(rfd);
|
||||
let err = try_select(&[&fd_arm]).unwrap_err();
|
||||
assert_eq!(err.kind(), std::io::ErrorKind::AlreadyExists);
|
||||
|
||||
// First waiter still wakes normally.
|
||||
assert_eq!(raw_write(wfd, b"w"), 1);
|
||||
let _ = h.join();
|
||||
ok2.store(true, Ordering::SeqCst);
|
||||
});
|
||||
assert_eq!(got.load(Ordering::SeqCst), b'w' as u32);
|
||||
assert!(ok.load(Ordering::SeqCst));
|
||||
}
|
||||
Reference in New Issue
Block a user