diff --git a/src/libcore/pipes.rs b/src/libcore/pipes.rs
index ae141cedc82..d6c5b32de59 100644
--- a/src/libcore/pipes.rs
+++ b/src/libcore/pipes.rs
@@ -11,7 +11,7 @@ enum state {
 
 type packet<T: send> = {
     mut state: state,
-    mut blocked_task: option<task::task>,
+    mut blocked_task: option<*rust_task>,
     mut payload: option<T>
 };
 
@@ -31,6 +31,19 @@ native mod rusti {
     fn atomic_xchng_rel(&dst: int, src: int) -> int;
 }
 
+type rust_task = libc::c_void;
+
+native mod rustrt {
+    #[rust_stack]
+    fn rust_get_task() -> *rust_task;
+
+    #[rust_stack]
+    fn task_clear_event_reject(task: *rust_task);
+
+    fn task_wait_event(this: *rust_task) -> *libc::c_void;
+    fn task_signal_event(target: *rust_task, event: *libc::c_void);
+}
+
 // We should consider moving this to core::unsafe, although I
 // suspect graydon would want us to use void pointers instead.
 unsafe fn uniquify<T>(x: *T) -> ~T {
@@ -54,8 +67,8 @@ fn swap_state_rel(&dst: state, src: state) -> state {
 }
 
 fn send<T: send>(-p: send_packet<T>, -payload: T) {
-    let p = p.unwrap();
-    let p = unsafe { uniquify(p) };
+    let p_ = p.unwrap();
+    let p = unsafe { uniquify(p_) };
     assert (*p).payload == none;
     (*p).payload <- some(payload);
     let old_state = swap_state_rel((*p).state, full);
@@ -68,8 +81,13 @@ fn send<T: send>(-p: send_packet<T>, -payload: T) {
       }
       full { fail "duplicate send" }
       blocked {
-        // TODO: once the target will actually block, tell the
-        // scheduler to wake it up.
+        #debug("waking up task for %?", p_);
+        alt p.blocked_task {
+          some(task) {
+            rustrt::task_signal_event(task, p_ as *libc::c_void);
+          }
+          none { fail "blocked packet has no task" }
+        }
 
         // The receiver will eventually clean this up.
         unsafe { forget(p); }
@@ -82,16 +100,32 @@ fn send<T: send>(-p: send_packet<T>, -payload: T) {
 }
 
 fn recv<T: send>(-p: recv_packet<T>) -> option<T> {
-    let p = p.unwrap();
-    let p = unsafe { uniquify(p) };
+    let p_ = p.unwrap();
+    let p = unsafe { uniquify(p_) };
+    let this = rustrt::rust_get_task();
+    rustrt::task_clear_event_reject(this);
+    p.blocked_task = some(this);
     loop {
         let old_state = swap_state_acq((*p).state,
                                        blocked);
+        #debug("%?", old_state);
         alt old_state {
-          empty | blocked { task::yield(); }
+          empty {
+            #debug("no data available on %?, going to sleep.", p_);
+            rustrt::task_wait_event(this);
+            #debug("woke up, p.state = %?", p.state);
+            if p.state == full {
+                let mut payload = none;
+                payload <-> (*p).payload;
+                p.state = terminated;
+                ret some(option::unwrap(payload))
+            }
+          }
+          blocked { fail "blocking on already blocked packet" }
           full {
             let mut payload = none;
             payload <-> (*p).payload;
+            p.state = terminated;
             ret some(option::unwrap(payload))
           }
           terminated {
diff --git a/src/libcore/task.rs b/src/libcore/task.rs
index fd69525d63e..7730ef8adfe 100644
--- a/src/libcore/task.rs
+++ b/src/libcore/task.rs
@@ -782,6 +782,7 @@ extern mod rustrt {
     fn rust_new_sched(num_threads: libc::uintptr_t) -> sched_id;
 
     fn get_task_id() -> task_id;
+    #[rust_stack]
     fn rust_get_task() -> *rust_task;
 
     fn new_task() -> *rust_task;
diff --git a/src/rt/rust_builtin.cpp b/src/rt/rust_builtin.cpp
index a33d3cb90fe..732dbaa3293 100644
--- a/src/rt/rust_builtin.cpp
+++ b/src/rt/rust_builtin.cpp
@@ -922,6 +922,26 @@ rust_task_local_data_atexit(rust_task *task, void (*cleanup_fn)(void *data)) {
     task->task_local_data_cleanup = cleanup_fn;
 }
 
+extern "C" void
+task_clear_event_reject(rust_task *task) {
+    task->clear_event_reject();
+}
+
+// Waits on an event, returning the pointer to the event that unblocked this
+// task.
+extern "C" void *
+task_wait_event(rust_task *task) {
+    // TODO: we should assert that the passed in task is the currently running
+    // task. We wouldn't want to wait some other task.
+
+    return task->wait_event();
+}
+
+extern "C" void
+task_signal_event(rust_task *target, void *event) {
+    target->signal_event(event);
+}
+
 //
 // Local Variables:
 // mode: C++
diff --git a/src/rt/rust_task.cpp b/src/rt/rust_task.cpp
index d7d43bcd27d..6a9f5cf5001 100644
--- a/src/rt/rust_task.cpp
+++ b/src/rt/rust_task.cpp
@@ -36,6 +36,8 @@ rust_task::rust_task(rust_sched_loop *sched_loop, rust_task_state state,
     state(state),
     cond(NULL),
     cond_name("none"),
+    event_reject(false),
+    event(NULL),
     killed(false),
     reentered_rust_stack(false),
     disallow_kill(0),
@@ -407,13 +409,20 @@ rust_task::free(void *p)
 void
 rust_task::transition(rust_task_state src, rust_task_state dst,
                       rust_cond *cond, const char* cond_name) {
+    scoped_lock with(state_lock);
+    transition_locked(src, dst, cond, cond_name);
+}
+
+void rust_task::transition_locked(rust_task_state src, rust_task_state dst,
+                                  rust_cond *cond, const char* cond_name) {
+    state_lock.must_have_lock();
     sched_loop->transition(this, src, dst, cond, cond_name);
 }
 
 void
 rust_task::set_state(rust_task_state state,
                      rust_cond *cond, const char* cond_name) {
-    scoped_lock with(state_lock);
+    state_lock.must_have_lock();
     this->state = state;
     this->cond = cond;
     this->cond_name = cond_name;
@@ -422,7 +431,11 @@ rust_task::set_state(rust_task_state state,
 bool
 rust_task::block(rust_cond *on, const char* name) {
     scoped_lock with(kill_lock);
+    return block_locked(on, name);
+}
 
+bool
+rust_task::block_locked(rust_cond *on, const char* name) {
     if (must_fail_from_being_killed_unlocked()) {
         // We're already going to die. Don't block. Tell the task to fail
         return false;
@@ -433,19 +446,25 @@ rust_task::block(rust_cond *on, const char* name) {
     assert(cond == NULL && "Cannot block an already blocked task.");
     assert(on != NULL && "Cannot block on a NULL object.");
 
-    transition(task_state_running, task_state_blocked, on, name);
+    transition_locked(task_state_running, task_state_blocked, on, name);
 
     return true;
 }
 
 void
 rust_task::wakeup(rust_cond *from) {
+    scoped_lock with(state_lock);
+    wakeup_locked(from);
+}
+
+void
+rust_task::wakeup_locked(rust_cond *from) {
     assert(cond != NULL && "Cannot wake up unblocked task.");
     LOG(this, task, "Blocked on 0x%" PRIxPTR " woken up on 0x%" PRIxPTR,
                         (uintptr_t) cond, (uintptr_t) from);
     assert(cond == from && "Cannot wake up blocked task on wrong condition.");
 
-    transition(task_state_blocked, task_state_running, NULL, "none");
+    transition_locked(task_state_blocked, task_state_running, NULL, "none");
 }
 
 void
@@ -693,6 +712,34 @@ rust_task::allow_kill() {
     disallow_kill--;
 }
 
+void *
+rust_task::wait_event() {
+    scoped_lock with(state_lock);
+
+    if(!event_reject) {
+        block_locked(&event_cond, "waiting on event");
+        bool killed = false;
+        state_lock.unlock();
+        yield(&killed);
+        state_lock.lock();
+        // TODO: what is the right thing to do if we are killed?
+    }
+
+    event_reject = false;
+    return event;
+}
+
+void
+rust_task::signal_event(void *event) {
+    scoped_lock with(state_lock);
+
+    this->event = event;
+    event_reject = true;
+    if(task_state_blocked == state) {
+        wakeup_locked(&event_cond);
+    }
+}
+
 //
 // Local Variables:
 // mode: C++
diff --git a/src/rt/rust_task.h b/src/rt/rust_task.h
index 96b0bddd4e0..c5bdc50e430 100644
--- a/src/rt/rust_task.h
+++ b/src/rt/rust_task.h
@@ -175,6 +175,10 @@ private:
     rust_cond *cond;
     const char *cond_name;
 
+    bool event_reject;
+    rust_cond event_cond;
+    void *event;
+
     // Protects the killed flag, disallow_kill flag, reentered_rust_stack
     lock_and_signal kill_lock;
     // Indicates that the task was killed and needs to unwind
@@ -205,6 +209,8 @@ private:
 
     void transition(rust_task_state src, rust_task_state dst,
                     rust_cond *cond, const char* cond_name);
+    void transition_locked(rust_task_state src, rust_task_state dst,
+                           rust_cond *cond, const char* cond_name);
 
     bool must_fail_from_being_killed_unlocked();
     // Called by rust_task_fail to unwind on failure
@@ -221,6 +227,9 @@ private:
                                char const *file,
                                size_t line);
 
+    bool block_locked(rust_cond *on, const char* name);
+    void wakeup_locked(rust_cond *from);
+
 public:
 
     // Only a pointer to 'name' is kept, so it must live as long as this task.
@@ -303,6 +312,13 @@ public:
     rust_cond *get_cond() { return cond; }
     const char *get_cond_name() { return cond_name; }
 
+    void clear_event_reject() {
+        this->event_reject = false;
+    }
+
+    void *wait_event();
+    void signal_event(void *event);
+
     void cleanup_after_turn();
 
     void inhibit_kill();
diff --git a/src/rt/rustrt.def.in b/src/rt/rustrt.def.in
index a218782dcbe..e674d6fa197 100644
--- a/src/rt/rustrt.def.in
+++ b/src/rt/rustrt.def.in
@@ -64,6 +64,9 @@ start_task
 vec_reserve_shared
 str_reserve_shared
 vec_from_buf_shared
+task_clear_event_reject
+task_wait_event
+task_signal_event
 unsupervise
 upcall_cmp_type
 upcall_fail