# HG changeset patch
# Parent  bd556f748cf8187c26d6e2a40986efbf557b4643
Issue #1621: Avoid overflow detected by test_threading

diff -r bd556f748cf8 Misc/NEWS
--- a/Misc/NEWS	Sat Jul 23 03:39:49 2016 +0000
+++ b/Misc/NEWS	Sat Jul 23 04:08:03 2016 +0000
@@ -38,7 +38,8 @@
 - Issue #27567: Expose the EPOLLRDHUP and POLLRDHUP constants in the select
   module.
 
-- Issue #1621: Avoid signed int negation overflow in the "audioop" module.
+- Issue #1621: Avoid signed integer overflow in the "audioop" and "_thread"
+  modules.
 
 - Issue #27533: Release GIL in nt._isdir
 
diff -r bd556f748cf8 Modules/_threadmodule.c
--- a/Modules/_threadmodule.c	Sat Jul 23 03:39:49 2016 +0000
+++ b/Modules/_threadmodule.c	Sat Jul 23 04:08:03 2016 +0000
@@ -52,11 +52,12 @@
 acquire_timed(PyThread_type_lock lock, _PyTime_t timeout)
 {
     PyLockStatus r;
-    _PyTime_t endtime = 0;
+    _PyTime_t starttime = 0; /* Always initialized to suppress warning */
     _PyTime_t microseconds;
 
-    if (timeout > 0)
-        endtime = _PyTime_GetMonotonicClock() + timeout;
+    if (timeout > 0) {
+        starttime = _PyTime_GetMonotonicClock();
+    }
 
     do {
         microseconds = _PyTime_AsMicroseconds(timeout, _PyTime_ROUND_CEILING);
@@ -80,13 +81,17 @@
             /* If we're using a timeout, recompute the timeout after processing
              * signals, since those can take time.  */
             if (timeout > 0) {
-                timeout = endtime - _PyTime_GetMonotonicClock();
+                _PyTime_t elapsed = _PyTime_GetMonotonicClock() - starttime;
 
                 /* Check for negative values, since those mean block forever.
                  */
-                if (timeout < 0) {
+                if (timeout < elapsed) {
                     r = PY_LOCK_FAILURE;
                 }
+                else {
+                    timeout -= elapsed;
+                    starttime += elapsed;
+                }
             }
         }
     } while (r == PY_LOCK_INTR);  /* Retry if we were interrupted. */