diff -r eee959fee5f5 Python/condvar.h
--- a/Python/condvar.h	Sat May 07 21:13:50 2016 +0300
+++ b/Python/condvar.h	Mon May 16 16:51:28 2016 +0200
@@ -94,15 +94,24 @@
     int r;
     struct timespec ts;
     struct timeval deadline;
+    struct timeval timedout;
+    static PY_LONG_LONG last_us = 0;
 
+    us = last_us > us ? last_us: us;
+    last_us = 0;
     PyCOND_GETTIMEOFDAY(&deadline);
     PyCOND_ADD_MICROSECONDS(deadline, us);
     ts.tv_sec = deadline.tv_sec;
     ts.tv_nsec = deadline.tv_usec * 1000;
 
     r = pthread_cond_timedwait((cond), (mut), &ts);
-    if (r == ETIMEDOUT)
+    if (r == ETIMEDOUT) {
+        PyCOND_GETTIMEOFDAY(&timedout);
+        if (timedout.tv_usec > deadline.tv_usec)
+            timedout.tv_usec += 100000;
+        last_us = timedout.tv_usec - deadline.tv_usec;
         return 1;
+    }
     else if (r)
         return -1;
     else