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

MartinAltmayer · Yury Selivanov · commit 944451cd8d3e · 2018-07-31T10:06:12.000-04:00
diff --git a/Doc/library/asyncio-eventloop.rst b/Doc/library/asyncio-eventloop.rst
@@ -173,10 +173,6 @@ Which clock is used depends on the (platform-specific) event loop
 implementation; ideally it is a monotonic clock.  This will generally be
 a different clock than :func:`time.time`.
 
-.. note::
-
-   Timeouts (relative *delay* or absolute *when*) should not exceed one day.
-
 
 .. method:: AbstractEventLoop.call_later(delay, callback, *args, context=None)
 
diff --git a/Lib/asyncio/base_events.py b/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
@@ -1708,7 +1711,7 @@ 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()
diff --git a/Misc/NEWS.d/next/Library/2018-07-28-17-00-36.bpo-34263.zUfRsu.rst b/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.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+asyncio's event loop will not pass timeouts longer than one day to`
	`2`	`+epoll/select etc.`