bpo-30768: Recompute timeout on interrupted lock (GH-4103)

Fix the pthread+semaphore implementation of
PyThread_acquire_lock_timed() when called with timeout > 0 and
intr_flag=0: recompute the timeout if sem_timedwait() is interrupted
by a signal (EINTR).

See also the PEP 475.

The pthread implementation of PyThread_acquire_lock() now fails with
a fatal error if the timeout is larger than PY_TIMEOUT_MAX, as done
in the Windows implementation.

The check prevents any risk of overflow in PyThread_acquire_lock().

Add also PY_DWORD_MAX constant.

1 files changed, 5 insertions, 4 deletions

diff --git a/Python/thread_nt.h b/Python/thread_nt.h
index bae8bcc..46df346 100644
--- a/Python/thread_nt.h
+++ b/Python/thread_nt.h
@@ -283,12 +283,13 @@ PyThread_acquire_lock_timed(PyThread_type_lock aLock,
         milliseconds = microseconds / 1000;
         if (microseconds % 1000 > 0)
             ++milliseconds;
-        if ((DWORD) milliseconds != milliseconds)
-            Py_FatalError("Timeout too large for a DWORD, "
-                           "please check PY_TIMEOUT_MAX");
+        if (milliseconds > PY_DWORD_MAX) {
+            Py_FatalError("Timeout larger than PY_TIMEOUT_MAX");
+        }
     }
-    else
+    else {
         milliseconds = INFINITE;
+    }
 
     dprintf(("%lu: PyThread_acquire_lock_timed(%p, %lld) called\n",
              PyThread_get_thread_ident(), aLock, microseconds));