From 5917ca35190b526b65b4d26ad0b98024ce9e0b09 Mon Sep 17 00:00:00 2001
From: Michael Bebenita <mbebenita@mozilla.com>
Date: Mon, 9 Aug 2010 08:06:08 -0700
Subject: [PATCH] Fixed deadlock in the scheduler caused by condition
 variables.

---
 src/rt/rust_dom.cpp    | 17 ++++++++++++-----
 src/rt/rust_dom.h      |  3 ---
 src/rt/rust_internal.h |  1 +
 src/rt/rust_task.cpp   |  3 ---
 4 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/rt/rust_dom.cpp b/src/rt/rust_dom.cpp
index f0739097ca0..b66fca829fb 100644
--- a/src/rt/rust_dom.cpp
+++ b/src/rt/rust_dom.cpp
@@ -262,8 +262,6 @@ void rust_dom::send_message(rust_message *message) {
                         this);
     A(this, message->dom == this, "Message owned by non-local domain.");
     _incoming_message_queue.enqueue(message);
-    _incoming_message_pending.signal();
-    _progress.signal();
 }
 
 /**
@@ -398,9 +396,11 @@ rust_dom::start_main_loop()
                 "all tasks are blocked, waiting for progress ...");
             if (_log.is_tracing(rust_log::TASK))
                 log_state();
-            _progress.wait();
             log(rust_log::TASK,
-                "progress made, resuming ...");
+                "all tasks are blocked, scheduler yielding ...");
+            sync::yield();
+            log(rust_log::TASK,
+                "scheduler resuming ...");
             continue;
         }
 
@@ -450,7 +450,14 @@ rust_dom::start_main_loop()
         }
 
         if (_incoming_message_queue.is_empty()) {
-            _incoming_message_pending.wait();
+            log(rust_log::DOM,
+                "waiting for %d dead tasks to become dereferenced, "
+                "scheduler yielding ...",
+                dead_tasks.length());
+            if (_log.is_tracing(rust_log::TASK)) {
+                log_state();
+            }
+            sync::yield();
         } else {
             drain_incoming_message_queue();
         }
diff --git a/src/rt/rust_dom.h b/src/rt/rust_dom.h
index 4f3a91dcc4b..5a3278b9cc0 100644
--- a/src/rt/rust_dom.h
+++ b/src/rt/rust_dom.h
@@ -34,13 +34,10 @@ struct rust_dom
     rust_task *curr_task;
     int rval;
 
-    condition_variable _progress;
-
     hash_map<rust_task *, rust_proxy<rust_task> *> _task_proxies;
     hash_map<rust_port *, rust_proxy<rust_port> *> _port_proxies;
 
     // Incoming messages from other domains.
-    condition_variable _incoming_message_pending;
     lock_free_queue _incoming_message_queue;
 
 #ifndef __WIN32__
diff --git a/src/rt/rust_internal.h b/src/rt/rust_internal.h
index 4f2d8902858..46ea843fcc2 100644
--- a/src/rt/rust_internal.h
+++ b/src/rt/rust_internal.h
@@ -38,6 +38,7 @@ extern "C" {
 #error "Platform not supported."
 #endif
 
+#include "sync/sync.h"
 #include "sync/condition_variable.h"
 
 #ifndef __i386__
diff --git a/src/rt/rust_task.cpp b/src/rt/rust_task.cpp
index 63724bbbcd3..c8831e8e05b 100644
--- a/src/rt/rust_task.cpp
+++ b/src/rt/rust_task.cpp
@@ -556,9 +556,6 @@ rust_task::wakeup(rust_cond *from)
     A(dom, cond == from, "Cannot wake up blocked task on wrong condition.");
 
     transition(&dom->blocked_tasks, &dom->running_tasks);
-    // TODO: Signaling every time the task is awaken is kind of silly,
-    // do this a nicer way.
-    dom->_progress.signal();
     I(dom, cond == from);
     cond = NULL;
 }