Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/crossbeam-epoch/tests/loom.rs

@@ -0,0 +1,157 @@
+#![cfg(crossbeam_loom)]
+
+use crossbeam_epoch as epoch;
+use loom_crate as loom;
+
+use epoch::*;
+use epoch::{Atomic, Owned};
+use loom::sync::atomic::Ordering::{self, Acquire, Relaxed, Release};
+use loom::sync::Arc;
+use loom::thread::spawn;
+use std::mem::ManuallyDrop;
+use std::ptr;
+
+#[test]
+fn it_works() {
+    loom::model(|| {
+        let collector = Collector::new();
+        let item: Atomic<String> = Atomic::from(Owned::new(String::from("boom")));
+        let item2 = item.clone();
+        let collector2 = collector.clone();
+        let guard = collector.register().pin();
+
+        let jh = loom::thread::spawn(move || {
+            let guard = collector2.register().pin();
+            guard.defer(move || {
+                // this isn't really safe, since other threads may still have pointers to the
+                // value, but in this limited test scenario it's okay, since we know the test won't
+                // access item after all the pins are released.
+                let mut item = unsafe { item2.into_owned() };
+                // mutate it as a second measure to make sure the assert_eq below would fail
+                item.retain(|c| c == 'o');
+                drop(item);
+            });
+        });
+
+        let item = item.load(Ordering::SeqCst, &guard);
+        // we pinned strictly before the call to defer_destroy,
+        // so item cannot have been dropped yet
+        assert_eq!(*unsafe { item.deref() }, "boom");
+        drop(guard);
+
+        jh.join().unwrap();
+
+        drop(collector);
+    })
+}
+
+#[test]
+fn treiber_stack() {
+    /// Treiber's lock-free stack.
+    ///
+    /// Usable with any number of producers and consumers.
+    #[derive(Debug)]
+    pub struct TreiberStack<T> {
+        head: Atomic<Node<T>>,
+    }
+
+    #[derive(Debug)]
+    struct Node<T> {
+        data: ManuallyDrop<T>,
+        next: Atomic<Node<T>>,
+    }
+
+    impl<T> TreiberStack<T> {
+        /// Creates a new, empty stack.
+        pub fn new() -> TreiberStack<T> {
+            TreiberStack {
+                head: Atomic::null(),
+            }
+        }
+
+        /// Pushes a value on top of the stack.
+        pub fn push(&self, t: T) {
+            let mut n = Owned::new(Node {
+                data: ManuallyDrop::new(t),
+                next: Atomic::null(),
+            });
+
+            let guard = epoch::pin();
+
+            loop {
+                let head = self.head.load(Relaxed, &guard);
+                n.next.store(head, Relaxed);
+
+                match self
+                    .head
+                    .compare_exchange(head, n, Release, Relaxed, &guard)
+                {
+                    Ok(_) => break,
+                    Err(e) => n = e.new,
+                }
+            }
+        }
+
+        /// Attempts to pop the top element from the stack.
+        ///
+        /// Returns `None` if the stack is empty.
+        pub fn pop(&self) -> Option<T> {
+            let guard = epoch::pin();
+            loop {
+                let head = self.head.load(Acquire, &guard);
+
+                match unsafe { head.as_ref() } {
+                    Some(h) => {
+                        let next = h.next.load(Relaxed, &guard);
+
+                        if self
+                            .head
+                            .compare_exchange(head, next, Relaxed, Relaxed, &guard)
+                            .is_ok()
+                        {
+                            unsafe {
+                                guard.defer_destroy(head);
+                                return Some(ManuallyDrop::into_inner(ptr::read(&(*h).data)));
+                            }
+                        }
+                    }
+                    None => return None,
+                }
+            }
+        }
+
+        /// Returns `true` if the stack is empty.
+        pub fn is_empty(&self) -> bool {
+            let guard = epoch::pin();
+            self.head.load(Acquire, &guard).is_null()
+        }
+    }
+
+    impl<T> Drop for TreiberStack<T> {
+        fn drop(&mut self) {
+            while self.pop().is_some() {}
+        }
+    }
+
+    loom::model(|| {
+        let stack1 = Arc::new(TreiberStack::new());
+        let stack2 = Arc::clone(&stack1);
+
+        // use 5 since it's greater than the 4 used for the sanitize feature
+        let jh = spawn(move || {
+            for i in 0..5 {
+                stack2.push(i);
+                assert!(stack2.pop().is_some());
+            }
+        });
+
+        for i in 0..5 {
+            stack1.push(i);
+            assert!(stack1.pop().is_some());
+        }
+
+        jh.join().unwrap();
+        assert!(stack1.pop().is_none());
+        assert!(stack1.is_empty());
+    });
+}