auto merge of #10080 : brson/rust/sched_queue, r=brson

Rebase and update of #9710

1 files changed, 205 insertions, 0 deletions

diff --git a/src/libstd/rt/mpsc_queue.rs b/src/libstd/rt/mpsc_queue.rs
new file mode 100644
index 00000000000..4f39a1df4fa
--- /dev/null
+++ b/src/libstd/rt/mpsc_queue.rs
@@ -0,0 +1,205 @@
+/* Multi-producer/single-consumer queue
+ * Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * The views and conclusions contained in the software and documentation are
+ * those of the authors and should not be interpreted as representing official
+ * policies, either expressed or implied, of Dmitry Vyukov.
+ */
+
+//! A mostly lock-free multi-producer, single consumer queue.
+// http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue
+
+use unstable::sync::UnsafeArc;
+use unstable::atomics::{AtomicPtr,Relaxed,Release,Acquire};
+use ptr::{mut_null, to_mut_unsafe_ptr};
+use cast;
+use option::*;
+use clone::Clone;
+use kinds::Send;
+
+struct Node<T> {
+    next: AtomicPtr<Node<T>>,
+    value: Option<T>,
+}
+
+impl<T> Node<T> {
+    fn empty() -> Node<T> {
+        Node{next: AtomicPtr::new(mut_null()), value: None}
+    }
+
+    fn with_value(value: T) -> Node<T> {
+        Node{next: AtomicPtr::new(mut_null()), value: Some(value)}
+    }
+}
+
+struct State<T> {
+    pad0: [u8, ..64],
+    head: AtomicPtr<Node<T>>,
+    pad1: [u8, ..64],
+    stub: Node<T>,
+    pad2: [u8, ..64],
+    tail: *mut Node<T>,
+    pad3: [u8, ..64],
+}
+
+struct Queue<T> {
+    priv state: UnsafeArc<State<T>>,
+}
+
+impl<T: Send> Clone for Queue<T> {
+    fn clone(&self) -> Queue<T> {
+        Queue {
+            state: self.state.clone()
+        }
+    }
+}
+
+impl<T: Send> State<T> {
+    pub fn new() -> State<T> {
+        State{
+            pad0: [0, ..64],
+            head: AtomicPtr::new(mut_null()),
+            pad1: [0, ..64],
+            stub: Node::<T>::empty(),
+            pad2: [0, ..64],
+            tail: mut_null(),
+            pad3: [0, ..64],
+        }
+    }
+
+    fn init(&mut self) {
+        let stub = self.get_stub_unsafe();
+        self.head.store(stub, Relaxed);
+        self.tail = stub;
+    }
+
+    fn get_stub_unsafe(&mut self) -> *mut Node<T> {
+        to_mut_unsafe_ptr(&mut self.stub)
+    }
+
+    fn push(&mut self, value: T) {
+        unsafe {
+            let node = cast::transmute(~Node::with_value(value));
+            self.push_node(node);
+        }
+    }
+
+    fn push_node(&mut self, node: *mut Node<T>) {
+        unsafe {
+            (*node).next.store(mut_null(), Release);
+            let prev = self.head.swap(node, Relaxed);
+            (*prev).next.store(node, Release);
+        }
+    }
+
+    fn pop(&mut self) -> Option<T> {
+        unsafe {
+            let mut tail = self.tail;
+            let mut next = (*tail).next.load(Acquire);
+            let stub = self.get_stub_unsafe();
+            if tail == stub {
+                if mut_null() == next {
+                    return None
+                }
+                self.tail = next;
+                tail = next;
+                next = (*next).next.load(Acquire);
+            }
+            if next != mut_null() {
+                let tail: ~Node<T> = cast::transmute(tail);
+                self.tail = next;
+                return tail.value
+            }
+            let head = self.head.load(Relaxed);
+            if tail != head {
+                return None
+            }
+            self.push_node(stub);
+            next = (*tail).next.load(Acquire);
+            if next != mut_null() {
+                let tail: ~Node<T> = cast::transmute(tail);
+                self.tail = next;
+                return tail.value
+            }
+        }
+        None
+    }
+}
+
+impl<T: Send> Queue<T> {
+    pub fn new() -> Queue<T> {
+        unsafe {
+            let q = Queue{state: UnsafeArc::new(State::new())};
+            (*q.state.get()).init();
+            q
+        }
+    }
+
+    pub fn push(&mut self, value: T) {
+        unsafe { (*self.state.get()).push(value) }
+    }
+
+    pub fn pop(&mut self) -> Option<T> {
+        unsafe{ (*self.state.get()).pop() }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use prelude::*;
+    use option::*;
+    use task;
+    use comm;
+    use super::Queue;
+
+    #[test]
+    fn test() {
+        let nthreads = 8u;
+        let nmsgs = 1000u;
+        let mut q = Queue::new();
+        assert_eq!(None, q.pop());
+
+        for _ in range(0, nthreads) {
+            let (port, chan)  = comm::stream();
+            chan.send(q.clone());
+            do task::spawn_sched(task::SingleThreaded) {
+                let mut q = port.recv();
+                for i in range(0, nmsgs) {
+                    q.push(i);
+                }
+            }
+        }
+
+        let mut i = 0u;
+        loop {
+            match q.pop() {
+                None => {},
+                Some(_) => {
+                    i += 1;
+                    if i == nthreads*nmsgs { break }
+                }
+            }
+        }
+    }
+}
+