Incorporate review comment

Author: kleisauke

system/lib/pthread/library_pthread.c

@@ -84,7 +84,8 @@ int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int prioceiling)
 static uint32_t dummyZeroAddress = 0;
 
 void emscripten_thread_sleep(double msecs) {
-  double target = emscripten_get_now() + msecs;
+  double now = emscripten_get_now();
+  double target = now + msecs;
 
   // If we have less than this many msecs left to wait, busy spin that instead.
   double min_ms_slice_to_sleep = 0.1;
@@ -95,20 +96,21 @@ void emscripten_thread_sleep(double msecs) {
   emscripten_conditional_set_current_thread_status(
     EM_THREAD_STATUS_RUNNING, EM_THREAD_STATUS_SLEEPING);
 
-  double ms_to_sleep;
   do {
     // Keep processing the main loop of the calling thread.
     __pthread_testcancel(); // pthreads spec: sleep is a cancellation point, so must test if this
                             // thread is cancelled during the sleep.
     emscripten_current_thread_process_queued_calls();
 
-    ms_to_sleep = target - emscripten_get_now();
+    now = emscripten_get_now();
+    double ms_to_sleep = target - now;
     if (ms_to_sleep < min_ms_slice_to_sleep)
       continue;
     if (ms_to_sleep > max_ms_slice_to_sleep)
       ms_to_sleep = max_ms_slice_to_sleep;
     emscripten_futex_wait(&dummyZeroAddress, 0, ms_to_sleep);
-  } while (ms_to_sleep > 0);
+    now = emscripten_get_now();
+  } while (now < target);
 
   emscripten_conditional_set_current_thread_status(
     EM_THREAD_STATUS_SLEEPING, EM_THREAD_STATUS_RUNNING);