add multi-producer multi-consumer bounded queue to use for sleeper list

3 files changed, 211 insertions, 56 deletions

diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 771b15588d0..d87580c83bf 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -139,6 +139,9 @@ 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;
 
diff --git a/src/libstd/rt/mpmc_bounded_queue.rs b/src/libstd/rt/mpmc_bounded_queue.rs
new file mode 100644
index 00000000000..8e6ac8f79c7
--- /dev/null
+++ b/src/libstd/rt/mpmc_bounded_queue.rs
@@ -0,0 +1,199 @@
+/* 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.
+ */
+
+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> {
+    buffer: ~[Node<T>],
+    mask: uint,
+    enqueue_pos: AtomicUint,
+    dequeue_pos: AtomicUint,
+}
+
+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 {
+            // use next power of 2 as capacity
+            2f64.pow(&((capacity as f64).log2().floor()+1f64)) as uint
+        } else {
+            capacity
+        };
+        let buffer = do vec::from_fn(capacity) |i:uint| {
+            Node{sequence:AtomicUint::new(i),value:None}
+        };
+        State{
+            buffer: buffer,
+            mask: capacity-1,
+            enqueue_pos: AtomicUint::new(0),
+            dequeue_pos: AtomicUint::new(0),
+        }
+    }
+
+    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());
+        }
+    }
+}
diff --git a/src/libstd/rt/sleeper_list.rs b/src/libstd/rt/sleeper_list.rs
index f4fdf15cda6..39c7431837f 100644
--- a/src/libstd/rt/sleeper_list.rs
+++ b/src/libstd/rt/sleeper_list.rs
@@ -11,84 +11,37 @@
 //! Maintains a shared list of sleeping schedulers. Schedulers
 //! use this to wake each other up.
 
-use container::Container;
-use vec::OwnedVector;
-use option::{Option, Some, None};
-use cell::Cell;
-use unstable::sync::{UnsafeArc, LittleLock};
 use rt::sched::SchedHandle;
+use rt::mpmc_bounded_queue::Queue;
+use option::*;
 use clone::Clone;
 
 pub struct SleeperList {
-    priv state: UnsafeArc<State>
-}
-
-struct State {
-    count: uint,
-    stack: ~[SchedHandle],
-    lock: LittleLock
+    priv q: Queue<SchedHandle>,
 }
 
 impl SleeperList {
     pub fn new() -> SleeperList {
-        SleeperList {
-            state: UnsafeArc::new(State {
-                count: 0,
-                stack: ~[],
-                lock: LittleLock::new()
-            })
-        }
+        SleeperList{q: Queue::with_capacity(8*1024)}
     }
 
-    pub fn push(&mut self, handle: SchedHandle) {
-        let handle = Cell::new(handle);
-        unsafe {
-            let state = self.state.get();
-            do (*state).lock.lock {
-                (*state).count += 1;
-                (*state).stack.push(handle.take());
-            }
-        }
+    pub fn push(&mut self, value: SchedHandle) {
+        assert!(self.q.push(value))
     }
 
     pub fn pop(&mut self) -> Option<SchedHandle> {
-        unsafe {
-            let state = self.state.get();
-            do (*state).lock.lock {
-                if !(*state).stack.is_empty() {
-                    (*state).count -= 1;
-                    Some((*state).stack.pop())
-                } else {
-                    None
-                }
-            }
-        }
+        self.q.pop()
     }
 
-    /// A pop that may sometimes miss enqueued elements, but is much faster
-    /// to give up without doing any synchronization
     pub fn casual_pop(&mut self) -> Option<SchedHandle> {
-        unsafe {
-            let state = self.state.get();
-            // NB: Unsynchronized check
-            if (*state).count == 0 { return None; }
-            do (*state).lock.lock {
-                if !(*state).stack.is_empty() {
-                    // NB: count is also protected by the lock
-                    (*state).count -= 1;
-                    Some((*state).stack.pop())
-                } else {
-                    None
-                }
-            }
-        }
+        self.q.pop()
     }
 }
 
 impl Clone for SleeperList {
     fn clone(&self) -> SleeperList {
         SleeperList {
-            state: self.state.clone()
+            q: self.q.clone()
         }
     }
 }