Fixed race in the rust kernel.

src/rt/rust_kernel.cpp

@@ -129,20 +129,25 @@ rust_kernel::log(uint32_t type_bits, char const *fmt, ...) {
 }
 
 void
-rust_kernel::start_kernel_loop() {
-    while (_interrupt_kernel_loop == false) {
-        message_queues.global.lock();
-        for (size_t i = 0; i < message_queues.length(); i++) {
-            rust_message_queue *queue = message_queues[i];
-            if (queue->is_associated() == false) {
-                rust_message *message = NULL;
-                while (queue->dequeue(&message)) {
-                    message->kernel_process();
-                    delete message;
-                }
+rust_kernel::pump_message_queues() {
+    message_queues.global.lock();
+    for (size_t i = 0; i < message_queues.length(); i++) {
+        rust_message_queue *queue = message_queues[i];
+        if (queue->is_associated() == false) {
+            rust_message *message = NULL;
+            while (queue->dequeue(&message)) {
+                message->kernel_process();
+                delete message;
             }
         }
-        message_queues.global.unlock();
+    }
+    message_queues.global.unlock();
+}
+
+void
+rust_kernel::start_kernel_loop() {
+    while (_interrupt_kernel_loop == false) {
+        pump_message_queues();
     }
 }
 
@@ -153,16 +158,24 @@ rust_kernel::run() {
     log(rust_log::KERN, "finished kernel loop");
 }
 
+void
+rust_kernel::terminate_kernel_loop() {
+    _interrupt_kernel_loop = true;
+    join();
+}
+
 rust_kernel::~rust_kernel() {
     K(_srv, domains.length() == 0,
       "Kernel has %d live domain(s), join all domains before killing "
        "the kernel.", domains.length());
 
-    // If the kernel loop is running, interrupt it, join and exit.
-    if (is_running()) {
-        _interrupt_kernel_loop = true;
-        join();
-    }
+    terminate_kernel_loop();
+
+    // It's possible that the message pump misses some messages because
+    // of races, so pump any remaining messages here. By now all domain
+    // threads should have been joined, so we shouldn't miss any more
+    // messages.
+    pump_message_queues();
 
     free_handles(_task_handles);
     free_handles(_port_handles);

src/rt/rust_kernel.h

@@ -60,6 +60,9 @@ class rust_kernel : public rust_thread {
      */
     spin_lock _message_queues_lock;
 
+    void terminate_kernel_loop();
+    void pump_message_queues();
+
 public:
 
     /**

src/rt/sync/sync.cpp

@@ -11,6 +11,10 @@ void sync::yield() {
 #endif
 }
 
+rust_thread::rust_thread() : _is_running(false) {
+    // Nop.
+}
+
 #if defined(__WIN32__)
 static DWORD WINAPI
 #elif defined(__GNUC__)
@@ -36,6 +40,7 @@ rust_thread::start() {
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
    pthread_create(&thread, &attr, rust_thread_start, (void *) this);
 #endif
+   _is_running = true;
 }
 
 void
@@ -46,10 +51,10 @@ rust_thread::join() {
    pthread_join(thread, NULL);
 #endif
    thread = 0;
+   _is_running = false;
 }
 
 bool
 rust_thread::is_running() {
-    // TODO: This may be broken because of possible races.
-    return thread;
+    return _is_running;
 }

src/rt/sync/sync.h

@@ -15,12 +15,15 @@ public:
  * Thread utility class. Derive and implement your own run() method.
  */
 class rust_thread {
+private:
+    volatile bool _is_running;
 public:
 #if defined(__WIN32__)
     HANDLE thread;
 #else
     pthread_t thread;
 #endif
+    rust_thread();
     void start();
 
     virtual void run() {

src/test/run-pass/task-comm-9.rs

@@ -16,7 +16,8 @@
     let port[int] p = port();
     let int number_of_messages = 10;
         
-    let task t0 = spawn thread test00_start(chan(p), number_of_messages);
+    let task t0 = spawn thread "child"
+        test00_start(chan(p), number_of_messages);
     
     let int i = 0;
     while (i < number_of_messages) {