[3.7] bpo-34263 Cap timeout submitted to epoll/select etc. to one day. (GH-8532) (GH-8586)

Author: miss-islington

Lib/asyncio/base_events.py

@@ -63,6 +63,9 @@
 
 _HAS_IPv6 = hasattr(socket, 'AF_INET6')
 
+# Maximum timeout passed to select to avoid OS limitations
+MAXIMUM_SELECT_TIMEOUT = 24 * 3600
+
 
 def _format_handle(handle):
     cb = handle._callback
@@ -1702,7 +1705,7 @@ def _run_once(self):
         elif self._scheduled:
             # Compute the desired timeout.
             when = self._scheduled[0]._when
-            timeout = max(0, when - self.time())
+            timeout = min(max(0, when - self.time()), MAXIMUM_SELECT_TIMEOUT)
 
         if self._debug and timeout != 0:
             t0 = self.time()

Misc/NEWS.d/next/Library/2018-07-28-17-00-36.bpo-34263.zUfRsu.rst

@@ -0,0 +1,2 @@
+asyncio's event loop will not pass timeouts longer than one day to
+epoll/select etc.