Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 411 insertions, 0 deletions

diff --git a/vendor/crossbeam-utils/src/sync/parker.rs b/vendor/crossbeam-utils/src/sync/parker.rs
new file mode 100644
index 000000000..531f5a5fc
--- /dev/null
+++ b/vendor/crossbeam-utils/src/sync/parker.rs
@@ -0,0 +1,411 @@
+use crate::primitive::sync::atomic::AtomicUsize;
+use crate::primitive::sync::{Arc, Condvar, Mutex};
+use core::sync::atomic::Ordering::SeqCst;
+use std::fmt;
+use std::marker::PhantomData;
+use std::time::{Duration, Instant};
+
+/// A thread parking primitive.
+///
+/// Conceptually, each `Parker` has an associated token which is initially not present:
+///
+/// * The [`park`] method blocks the current thread unless or until the token is available, at
+///   which point it automatically consumes the token.
+///
+/// * The [`park_timeout`] and [`park_deadline`] methods work the same as [`park`], but block for
+///   a specified maximum time.
+///
+/// * The [`unpark`] method atomically makes the token available if it wasn't already. Because the
+///   token is initially absent, [`unpark`] followed by [`park`] will result in the second call
+///   returning immediately.
+///
+/// In other words, each `Parker` acts a bit like a spinlock that can be locked and unlocked using
+/// [`park`] and [`unpark`].
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_utils::sync::Parker;
+///
+/// let p = Parker::new();
+/// let u = p.unparker().clone();
+///
+/// // Make the token available.
+/// u.unpark();
+/// // Wakes up immediately and consumes the token.
+/// p.park();
+///
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_millis(500));
+///     u.unpark();
+/// });
+///
+/// // Wakes up when `u.unpark()` provides the token.
+/// p.park();
+/// ```
+///
+/// [`park`]: Parker::park
+/// [`park_timeout`]: Parker::park_timeout
+/// [`park_deadline`]: Parker::park_deadline
+/// [`unpark`]: Unparker::unpark
+pub struct Parker {
+    unparker: Unparker,
+    _marker: PhantomData<*const ()>,
+}
+
+unsafe impl Send for Parker {}
+
+impl Default for Parker {
+    fn default() -> Self {
+        Self {
+            unparker: Unparker {
+                inner: Arc::new(Inner {
+                    state: AtomicUsize::new(EMPTY),
+                    lock: Mutex::new(()),
+                    cvar: Condvar::new(),
+                }),
+            },
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl Parker {
+    /// Creates a new `Parker`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// ```
+    ///
+    pub fn new() -> Parker {
+        Self::default()
+    }
+
+    /// Blocks the current thread until the token is made available.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let u = p.unparker().clone();
+    ///
+    /// // Make the token available.
+    /// u.unpark();
+    ///
+    /// // Wakes up immediately and consumes the token.
+    /// p.park();
+    /// ```
+    pub fn park(&self) {
+        self.unparker.inner.park(None);
+    }
+
+    /// Blocks the current thread until the token is made available, but only for a limited time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    ///
+    /// // Waits for the token to become available, but will not wait longer than 500 ms.
+    /// p.park_timeout(Duration::from_millis(500));
+    /// ```
+    pub fn park_timeout(&self, timeout: Duration) {
+        self.park_deadline(Instant::now() + timeout)
+    }
+
+    /// Blocks the current thread until the token is made available, or until a certain deadline.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::{Duration, Instant};
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let deadline = Instant::now() + Duration::from_millis(500);
+    ///
+    /// // Waits for the token to become available, but will not wait longer than 500 ms.
+    /// p.park_deadline(deadline);
+    /// ```
+    pub fn park_deadline(&self, deadline: Instant) {
+        self.unparker.inner.park(Some(deadline))
+    }
+
+    /// Returns a reference to an associated [`Unparker`].
+    ///
+    /// The returned [`Unparker`] doesn't have to be used by reference - it can also be cloned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let u = p.unparker().clone();
+    ///
+    /// // Make the token available.
+    /// u.unpark();
+    /// // Wakes up immediately and consumes the token.
+    /// p.park();
+    /// ```
+    ///
+    /// [`park`]: Parker::park
+    /// [`park_timeout`]: Parker::park_timeout
+    pub fn unparker(&self) -> &Unparker {
+        &self.unparker
+    }
+
+    /// Converts a `Parker` into a raw pointer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let raw = Parker::into_raw(p);
+    /// # let _ = unsafe { Parker::from_raw(raw) };
+    /// ```
+    pub fn into_raw(this: Parker) -> *const () {
+        Unparker::into_raw(this.unparker)
+    }
+
+    /// Converts a raw pointer into a `Parker`.
+    ///
+    /// # Safety
+    ///
+    /// This method is safe to use only with pointers returned by [`Parker::into_raw`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let raw = Parker::into_raw(p);
+    /// let p = unsafe { Parker::from_raw(raw) };
+    /// ```
+    pub unsafe fn from_raw(ptr: *const ()) -> Parker {
+        Parker {
+            unparker: Unparker::from_raw(ptr),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl fmt::Debug for Parker {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Parker { .. }")
+    }
+}
+
+/// Unparks a thread parked by the associated [`Parker`].
+pub struct Unparker {
+    inner: Arc<Inner>,
+}
+
+unsafe impl Send for Unparker {}
+unsafe impl Sync for Unparker {}
+
+impl Unparker {
+    /// Atomically makes the token available if it is not already.
+    ///
+    /// This method will wake up the thread blocked on [`park`] or [`park_timeout`], if there is
+    /// any.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_utils::sync::Parker;
+    ///
+    /// let p = Parker::new();
+    /// let u = p.unparker().clone();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_millis(500));
+    ///     u.unpark();
+    /// });
+    ///
+    /// // Wakes up when `u.unpark()` provides the token.
+    /// p.park();
+    /// ```
+    ///
+    /// [`park`]: Parker::park
+    /// [`park_timeout`]: Parker::park_timeout
+    pub fn unpark(&self) {
+        self.inner.unpark()
+    }
+
+    /// Converts an `Unparker` into a raw pointer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::{Parker, Unparker};
+    ///
+    /// let p = Parker::new();
+    /// let u = p.unparker().clone();
+    /// let raw = Unparker::into_raw(u);
+    /// # let _ = unsafe { Unparker::from_raw(raw) };
+    /// ```
+    pub fn into_raw(this: Unparker) -> *const () {
+        Arc::into_raw(this.inner) as *const ()
+    }
+
+    /// Converts a raw pointer into an `Unparker`.
+    ///
+    /// # Safety
+    ///
+    /// This method is safe to use only with pointers returned by [`Unparker::into_raw`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_utils::sync::{Parker, Unparker};
+    ///
+    /// let p = Parker::new();
+    /// let u = p.unparker().clone();
+    ///
+    /// let raw = Unparker::into_raw(u);
+    /// let u = unsafe { Unparker::from_raw(raw) };
+    /// ```
+    pub unsafe fn from_raw(ptr: *const ()) -> Unparker {
+        Unparker {
+            inner: Arc::from_raw(ptr as *const Inner),
+        }
+    }
+}
+
+impl fmt::Debug for Unparker {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Unparker { .. }")
+    }
+}
+
+impl Clone for Unparker {
+    fn clone(&self) -> Unparker {
+        Unparker {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+const EMPTY: usize = 0;
+const PARKED: usize = 1;
+const NOTIFIED: usize = 2;
+
+struct Inner {
+    state: AtomicUsize,
+    lock: Mutex<()>,
+    cvar: Condvar,
+}
+
+impl Inner {
+    fn park(&self, deadline: Option<Instant>) {
+        // If we were previously notified then we consume this notification and return quickly.
+        if self
+            .state
+            .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst)
+            .is_ok()
+        {
+            return;
+        }
+
+        // If the timeout is zero, then there is no need to actually block.
+        if let Some(deadline) = deadline {
+            if deadline <= Instant::now() {
+                return;
+            }
+        }
+
+        // Otherwise we need to coordinate going to sleep.
+        let mut m = self.lock.lock().unwrap();
+
+        match self.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
+            Ok(_) => {}
+            // Consume this notification to avoid spurious wakeups in the next park.
+            Err(NOTIFIED) => {
+                // We must read `state` here, even though we know it will be `NOTIFIED`. This is
+                // because `unpark` may have been called again since we read `NOTIFIED` in the
+                // `compare_exchange` above. We must perform an acquire operation that synchronizes
+                // with that `unpark` to observe any writes it made before the call to `unpark`. To
+                // do that we must read from the write it made to `state`.
+                let old = self.state.swap(EMPTY, SeqCst);
+                assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
+                return;
+            }
+            Err(n) => panic!("inconsistent park_timeout state: {}", n),
+        }
+
+        loop {
+            // Block the current thread on the conditional variable.
+            m = match deadline {
+                None => self.cvar.wait(m).unwrap(),
+                Some(deadline) => {
+                    let now = Instant::now();
+                    if now < deadline {
+                        // We could check for a timeout here, in the return value of wait_timeout,
+                        // but in the case that a timeout and an unpark arrive simultaneously, we
+                        // prefer to report the former.
+                        self.cvar.wait_timeout(m, deadline - now).unwrap().0
+                    } else {
+                        // We've timed out; swap out the state back to empty on our way out
+                        match self.state.swap(EMPTY, SeqCst) {
+                            NOTIFIED | PARKED => return,
+                            n => panic!("inconsistent park_timeout state: {}", n),
+                        };
+                    }
+                }
+            };
+
+            if self
+                .state
+                .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst)
+                .is_ok()
+            {
+                // got a notification
+                return;
+            }
+
+            // Spurious wakeup, go back to sleep. Alternatively, if we timed out, it will be caught
+            // in the branch above, when we discover the deadline is in the past
+        }
+    }
+
+    pub(crate) fn unpark(&self) {
+        // To ensure the unparked thread will observe any writes we made before this call, we must
+        // perform a release operation that `park` can synchronize with. To do that we must write
+        // `NOTIFIED` even if `state` is already `NOTIFIED`. That is why this must be a swap rather
+        // than a compare-and-swap that returns if it reads `NOTIFIED` on failure.
+        match self.state.swap(NOTIFIED, SeqCst) {
+            EMPTY => return,    // no one was waiting
+            NOTIFIED => return, // already unparked
+            PARKED => {}        // gotta go wake someone up
+            _ => panic!("inconsistent state in unpark"),
+        }
+
+        // There is a period between when the parked thread sets `state` to `PARKED` (or last
+        // checked `state` in the case of a spurious wakeup) and when it actually waits on `cvar`.
+        // If we were to notify during this period it would be ignored and then when the parked
+        // thread went to sleep it would never wake up. Fortunately, it has `lock` locked at this
+        // stage so we can acquire `lock` to wait until it is ready to receive the notification.
+        //
+        // Releasing `lock` before the call to `notify_one` means that when the parked thread wakes
+        // it doesn't get woken only to have to wait for us to release `lock`.
+        drop(self.lock.lock().unwrap());
+        self.cvar.notify_one();
+    }
+}