Merge pull request #495 from lf-lang/static-use-lf-sleep

[STATIC SCHEDULER] Use lf_sleep instead of busywait

core/threaded/scheduler_static.c

@@ -275,27 +275,20 @@ void execute_inst_DU(lf_scheduler_t* scheduler, size_t worker_number, operand_t
     int pc_orig = (int) *pc;
     tracepoint_static_scheduler_DU_starts(worker_number, pc_orig);
 #endif
-    // FIXME: There seems to be an overflow problem.
-    // When wakeup_time overflows but lf_time_physical() doesn't,
-    // _lf_interruptable_sleep_until_locked() terminates immediately.
     reg_t *src = op1.reg;
-    instant_t current_time = lf_time_physical();
     instant_t wakeup_time = *src + op2.imm;
     LF_PRINT_DEBUG("DU wakeup time: %lld, base: %lld, offset: %lld", wakeup_time, *src, op2.imm);
+    // Check if we need to sleep.
+    instant_t current_time;
+    _lf_clock_gettime(&current_time);
     instant_t wait_interval = wakeup_time - current_time;
-    // LF_PRINT_DEBUG("*** start_time: %lld, wakeup_time: %lld, op1: %lld, op2: %lld, current_physical_time: %lld\n", start_time, wakeup_time, *src, op2.imm, lf_time_physical());
-    LF_PRINT_DEBUG("*** [Line %zu] Worker %zu delaying, current_physical_time: %lld, wakeup_time: %lld, wait_interval: %lld", *pc, worker_number, current_time, wakeup_time, wait_interval);
+    LF_PRINT_DEBUG(
+      "*** [Line %zu] Worker %zu delaying, current_physical_time: %lld, wakeup_time: %lld, wait_interval: %lld", *pc,
+      worker_number, current_time, wakeup_time, wait_interval);
     if (wait_interval > 0) {
-        // Approach 1: Only spin when the wait interval is less than SPIN_WAIT_THRESHOLD.
-        if (wait_interval < SPIN_WAIT_THRESHOLD) {
-            // Spin wait if the wait interval is less than 1 ms.
-            while (lf_time_physical() < wakeup_time);
-        } else {
-            // Otherwise sleep.
-            _lf_interruptable_sleep_until_locked(scheduler->env, wakeup_time);
-        }
-        // Approach 2: Spin wait.
-        // while (lf_time_physical() < wakeup_time);
+      // Recalculate the wakeup time for max accuracy.
+      _lf_clock_gettime(&current_time);
+      lf_sleep(wakeup_time - current_time);
     }
     LF_PRINT_DEBUG("*** [Line %zu] Worker %zu done delaying", *pc, worker_number);
     *pc += 1; // Increment pc.