disabled the sleep mechanism in pool_work_until()

Author: wjakob

src/nanothread.cpp

@@ -337,10 +337,11 @@ Task *task_submit_dep(Pool *pool, const Task *const *parent,
 }
 
 static void pool_execute_task(Pool *pool, bool (*stopping_criterion)(void *),
-                              void *payload) {
+                              void *payload, bool may_sleep) {
     Task *task;
     uint32_t index;
-    std::tie(task, index) = pool->queue.pop_or_sleep(stopping_criterion, payload);
+    std::tie(task, index) =
+        pool->queue.pop_or_sleep(stopping_criterion, payload, may_sleep);
 
     if (task) {
         if (task->func) {
@@ -375,7 +376,7 @@ void pool_work_until(Pool *pool, bool (*stopping_criterion)(void *), void *paylo
     if (!pool)
         return;
     while (!stopping_criterion(payload))
-        pool_execute_task(pool, stopping_criterion, payload);
+        pool_execute_task(pool, stopping_criterion, payload, false);
 }
 
 #if defined(__SSE2__)
@@ -415,7 +416,7 @@ void task_wait(Task *task) {
 
         // Help executing work units in the meantime
         while (!stopping_criterion(task))
-            pool_execute_task(pool, stopping_criterion, task);
+            pool_execute_task(pool, stopping_criterion, task, true);
 
         task->wait_count--;
 
@@ -496,7 +497,8 @@ void Worker::run() {
     FTZGuard ftz_guard(ftz);
     while (!stop)
         pool_execute_task(
-            pool, [](void *ptr) -> bool { return *((bool *) ptr); }, &stop);
+            pool, [](void *ptr) -> bool { return *((bool *) ptr); }, &stop,
+            true);
 
     NT_TRACE("worker stopped");
 

src/queue.cpp

@@ -415,9 +415,11 @@ double time_milliseconds() {
 }
 #endif
 
-std::pair<Task *, uint32_t> TaskQueue::pop_or_sleep(bool (*stopping_criterion)(void *), void *payload) {
-    std::pair<Task *, uint32_t> result(nullptr, 0);
-    uint32_t attempts = 0;
+std::pair<Task *, uint32_t>
+TaskQueue::pop_or_sleep(bool (*stopping_criterion)(void *), void *payload,
+                        bool may_sleep) {
+        std::pair<Task *, uint32_t> result(nullptr, 0);
+        uint32_t attempts = 0;
 
 #if defined(NT_DEBUG)
     double start = time_milliseconds();
@@ -431,7 +433,7 @@ std::pair<Task *, uint32_t> TaskQueue::pop_or_sleep(bool (*stopping_criterion)(v
 
         attempts++;
 
-        if (attempts >= NANOTHREAD_MAX_ATTEMPTS) {
+        if (may_sleep && attempts >= NANOTHREAD_MAX_ATTEMPTS) {
             std::unique_lock<std::mutex> guard(sleep_mutex);
 
             uint64_t value = ++sleep_state, phase = value & high_mask;

src/queue.h

@@ -212,13 +212,15 @@ struct TaskQueue {
      * \breif Fetch a task from the queue, or sleep
      *
      * This function repeatedly tries to fetch work from the queue and sleeps
-     * if no work is available for an extended amount of time (~50 ms).
+     * if no work is available for an extended amount of time (~50 ms) and
+     * the \c may_sleep parameter is set to \c true.
      *
      * The function stops trying to acquire work and returns <tt>(nullptr,
      * 0)</tt> when the supplied function <tt>stopping_criterion(payload)</tt>
      * evaluates to true.
      */
-    std::pair<Task *, uint32_t> pop_or_sleep(bool (*stopping_criterion)(void *), void *payload);
+    std::pair<Task *, uint32_t> pop_or_sleep(bool (*stopping_criterion)(void *),
+                                             void *payload, bool may_sleep);
 
     /// Wake sleeping threads
     void wakeup();