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

Rebase and update of #9710

Author: bors

src/etc/licenseck.py

@@ -76,6 +76,8 @@
     "rt/isaac/randport.cpp", # public domain
     "rt/isaac/rand.h", # public domain
     "rt/isaac/standard.h", # public domain
+    "libstd/rt/mpsc_queue.rs", # BSD
+    "libstd/rt/mpmc_bounded_queue.rs", # BSD
 ]
 
 def check_license(name, contents):

src/libstd/rt/message_queue.rs

@@ -11,83 +11,45 @@
 //! A concurrent queue that supports multiple producers and a
 //! single consumer.
 
-use container::Container;
 use kinds::Send;
 use vec::OwnedVector;
-use cell::Cell;
-use option::*;
-use unstable::sync::{UnsafeArc, LittleLock};
+use option::Option;
 use clone::Clone;
+use rt::mpsc_queue::Queue;
 
 pub struct MessageQueue<T> {
-    priv state: UnsafeArc<State<T>>
-}
-
-struct State<T> {
-    count: uint,
-    queue: ~[T],
-    lock: LittleLock
+    priv queue: Queue<T>
 }
 
 impl<T: Send> MessageQueue<T> {
     pub fn new() -> MessageQueue<T> {
         MessageQueue {
-            state: UnsafeArc::new(State {
-                count: 0,
-                queue: ~[],
-                lock: LittleLock::new()
-            })
+            queue: Queue::new()
         }
     }
 
+    #[inline]
     pub fn push(&mut self, value: T) {
-        unsafe {
-            let value = Cell::new(value);
-            let state = self.state.get();
-            do (*state).lock.lock {
-                (*state).count += 1;
-                (*state).queue.push(value.take());
-            }
-        }
+        self.queue.push(value)
     }
 
+    #[inline]
     pub fn pop(&mut self) -> Option<T> {
-        unsafe {
-            let state = self.state.get();
-            do (*state).lock.lock {
-                if !(*state).queue.is_empty() {
-                    (*state).count += 1;
-                    Some((*state).queue.shift())
-                } else {
-                    None
-                }
-            }
-        }
+        self.queue.pop()
     }
 
     /// A pop that may sometimes miss enqueued elements, but is much faster
     /// to give up without doing any synchronization
+    #[inline]
     pub fn casual_pop(&mut self) -> Option<T> {
-        unsafe {
-            let state = self.state.get();
-            // NB: Unsynchronized check
-            if (*state).count == 0 { return None; }
-            do (*state).lock.lock {
-                if !(*state).queue.is_empty() {
-                    (*state).count += 1;
-                    Some((*state).queue.shift())
-                } else {
-                    None
-                }
-            }
-        }
+        self.queue.pop()
     }
 }
 
 impl<T: Send> Clone for MessageQueue<T> {
     fn clone(&self) -> MessageQueue<T> {
         MessageQueue {
-            state: self.state.clone()
+            queue: self.queue.clone()
         }
     }
 }

src/libstd/rt/mod.rs

@@ -136,6 +136,12 @@ mod work_queue;
 /// A parallel queue.
 mod message_queue;
 
+/// A mostly lock-free multi-producer, single consumer queue.
+mod mpsc_queue;
+
+/// A lock-free multi-producer, multi-consumer bounded queue.
+mod mpmc_bounded_queue;
+
 /// A parallel data structure for tracking sleeping schedulers.
 mod sleeper_list;
 

src/libstd/rt/mpmc_bounded_queue.rs

@@ -0,0 +1,213 @@
+/* Multi-producer/multi-consumer bounded 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.
+ */
+
+// http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
+
+use unstable::sync::UnsafeArc;
+use unstable::atomics::{AtomicUint,Relaxed,Release,Acquire};
+use option::*;
+use vec;
+use clone::Clone;
+use kinds::Send;
+use num::{Exponential,Algebraic,Round};
+
+struct Node<T> {
+    sequence: AtomicUint,
+    value: Option<T>,
+}
+
+struct State<T> {
+    pad0: [u8, ..64],
+    buffer: ~[Node<T>],
+    mask: uint,
+    pad1: [u8, ..64],
+    enqueue_pos: AtomicUint,
+    pad2: [u8, ..64],
+    dequeue_pos: AtomicUint,
+    pad3: [u8, ..64],
+}
+
+struct Queue<T> {
+    priv state: UnsafeArc<State<T>>,
+}
+
+impl<T: Send> State<T> {
+    fn with_capacity(capacity: uint) -> State<T> {
+        let capacity = if capacity < 2 || (capacity & (capacity - 1)) != 0 {
+            if capacity < 2 {
+                2u
+            } else {
+                // use next power of 2 as capacity
+                2f64.pow(&((capacity as f64).log2().ceil())) as uint
+            }
+        } else {
+            capacity
+        };
+        let buffer = do vec::from_fn(capacity) |i:uint| {
+            Node{sequence:AtomicUint::new(i),value:None}
+        };
+        State{
+            pad0: [0, ..64],
+            buffer: buffer,
+            mask: capacity-1,
+            pad1: [0, ..64],
+            enqueue_pos: AtomicUint::new(0),
+            pad2: [0, ..64],
+            dequeue_pos: AtomicUint::new(0),
+            pad3: [0, ..64],
+        }
+    }
+
+    fn push(&mut self, value: T) -> bool {
+        let mask = self.mask;
+        let mut pos = self.enqueue_pos.load(Relaxed);
+        loop {
+            let node = &mut self.buffer[pos & mask];
+            let seq = node.sequence.load(Acquire);
+            let diff: int = seq as int - pos as int;
+
+            if diff == 0 {
+                let enqueue_pos = self.enqueue_pos.compare_and_swap(pos, pos+1, Relaxed);
+                if enqueue_pos == pos {
+                    node.value = Some(value);
+                    node.sequence.store(pos+1, Release);
+                    break
+                } else {
+                    pos = enqueue_pos;
+                }
+            } else if (diff < 0) {
+                return false
+            } else {
+                pos = self.enqueue_pos.load(Relaxed);
+            }
+        }
+        true
+    }
+
+    fn pop(&mut self) -> Option<T> {
+        let mask = self.mask;
+        let mut pos = self.dequeue_pos.load(Relaxed);
+        loop {
+            let node = &mut self.buffer[pos & mask];
+            let seq = node.sequence.load(Acquire);
+            let diff: int = seq as int - (pos + 1) as int;
+            if diff == 0 {
+                let dequeue_pos = self.dequeue_pos.compare_and_swap(pos, pos+1, Relaxed);
+                if dequeue_pos == pos {
+                    let value = node.value.take();
+                    node.sequence.store(pos + mask + 1, Release);
+                    return value
+                } else {
+                    pos = dequeue_pos;
+                }
+            } else if diff < 0 {
+                return None
+            } else {
+                pos = self.dequeue_pos.load(Relaxed);
+            }
+        }
+    }
+}
+
+impl<T: Send> Queue<T> {
+    pub fn with_capacity(capacity: uint) -> Queue<T> {
+        Queue{
+            state: UnsafeArc::new(State::with_capacity(capacity))
+        }
+    }
+
+    pub fn push(&mut self, value: T) -> bool {
+        unsafe { (*self.state.get()).push(value) }
+    }
+
+    pub fn pop(&mut self) -> Option<T> {
+        unsafe { (*self.state.get()).pop() }
+    }
+}
+
+impl<T: Send> Clone for Queue<T> {
+    fn clone(&self) -> Queue<T> {
+        Queue {
+            state: self.state.clone()
+        }
+    }
+}
+
+#[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::with_capacity(nthreads*nmsgs);
+        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) {
+                    assert!(q.push(i));
+                }
+            }
+        }
+
+        let mut completion_ports = ~[];
+        for _ in range(0, nthreads) {
+            let (completion_port, completion_chan) = comm::stream();
+            completion_ports.push(completion_port);
+            let (port, chan)  = comm::stream();
+            chan.send(q.clone());
+            do task::spawn_sched(task::SingleThreaded) {
+                let mut q = port.recv();
+                let mut i = 0u;
+                loop {
+                    match q.pop() {
+                        None => {},
+                        Some(_) => {
+                            i += 1;
+                            if i == nmsgs { break }
+                        }
+                    }
+                }
+                completion_chan.send(i);
+            }
+        }
+
+        for completion_port in completion_ports.iter() {
+            assert_eq!(nmsgs, completion_port.recv());
+        }
+    }
+}