Initial vendor packages

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

vendor/crossbeam-epoch/examples/sanitize.rs

@@ -0,0 +1,66 @@
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering::{AcqRel, Acquire, Relaxed};
+use std::sync::Arc;
+use std::thread;
+use std::time::{Duration, Instant};
+
+use crossbeam_epoch::{self as epoch, Atomic, Collector, LocalHandle, Owned, Shared};
+use rand::Rng;
+
+fn worker(a: Arc<Atomic<AtomicUsize>>, handle: LocalHandle) -> usize {
+    let mut rng = rand::thread_rng();
+    let mut sum = 0;
+
+    if rng.gen() {
+        thread::sleep(Duration::from_millis(1));
+    }
+    let timeout = Duration::from_millis(rng.gen_range(0..10));
+    let now = Instant::now();
+
+    while now.elapsed() < timeout {
+        for _ in 0..100 {
+            let guard = &handle.pin();
+            guard.flush();
+
+            let val = if rng.gen() {
+                let p = a.swap(Owned::new(AtomicUsize::new(sum)), AcqRel, guard);
+                unsafe {
+                    guard.defer_destroy(p);
+                    guard.flush();
+                    p.deref().load(Relaxed)
+                }
+            } else {
+                let p = a.load(Acquire, guard);
+                unsafe { p.deref().fetch_add(sum, Relaxed) }
+            };
+
+            sum = sum.wrapping_add(val);
+        }
+    }
+
+    sum
+}
+
+fn main() {
+    for _ in 0..100 {
+        let collector = Collector::new();
+        let a = Arc::new(Atomic::new(AtomicUsize::new(777)));
+
+        let threads = (0..16)
+            .map(|_| {
+                let a = a.clone();
+                let c = collector.clone();
+                thread::spawn(move || worker(a, c.register()))
+            })
+            .collect::<Vec<_>>();
+
+        for t in threads {
+            t.join().unwrap();
+        }
+
+        unsafe {
+            a.swap(Shared::null(), AcqRel, epoch::unprotected())
+                .into_owned();
+        }
+    }
+}