bpo-28087: Detect broken poll() on macOS Sierra

vstinner · vstinner · commit e03f8f021134 · 2017-05-03T12:00:26.000+02:00
On macOS, check for broken poll() at runtime on macOS Sierra
16.0.x-16.5.x.

Disable select.poll() (remove select.poll) if poll() is broken.

Reenable select.poll() tests in test_asyncore and test_eintr
on macOS.
diff --git a/Lib/test/eintrdata/eintr_tester.py b/Lib/test/eintrdata/eintr_tester.py
@@ -442,8 +442,6 @@ def test_select(self):
         self.stop_alarm()
         self.assertGreaterEqual(dt, self.sleep_time)
 
-    @unittest.skipIf(sys.platform == "darwin",
-                     "poll may fail on macOS; see issue #28087")
     @unittest.skipUnless(hasattr(select, 'poll'), 'need select.poll')
     def test_poll(self):
         poller = select.poll()
diff --git a/Lib/test/test_asyncore.py b/Lib/test/test_asyncore.py
@@ -661,9 +661,6 @@ def test_handle_expt(self):
         if HAS_UNIX_SOCKETS and self.family == socket.AF_UNIX:
             self.skipTest("Not applicable to AF_UNIX sockets.")
 
-        if sys.platform == "darwin" and self.use_poll:
-            self.skipTest("poll may fail on macOS; see issue #28087")
-
         class TestClient(BaseClient):
             def handle_expt(self):
                 self.socket.recv(1024, socket.MSG_OOB)
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -317,6 +317,10 @@ Extension Modules
 Library
 -------
 
+- bpo-28087: On macOS, check for broken poll() at runtime on macOS Sierra
+  16.0.x-16.5.x. Disable select.poll() (remove select.poll) if poll() is
+  broken.
+
 - bpo-30103: binascii.b2a_uu() and uu.encode() now support using ``'`'``
   as zero instead of space.
 
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
@@ -12,11 +12,14 @@
 #include <structmember.h>
 
 #ifdef HAVE_SYS_DEVPOLL_H
-#include <sys/resource.h>
-#include <sys/devpoll.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
+#  include <sys/resource.h>
+#  include <sys/devpoll.h>
+#  include <sys/types.h>
+#  include <sys/stat.h>
+#  include <fcntl.h>
+#endif
+#ifdef __APPLE__
+#  include <sys/utsname.h>   /* select_have_broken_poll() */
 #endif
 
 #ifdef __APPLE__
@@ -1182,10 +1185,27 @@ select_devpoll(PyObject *self, PyObject *unused)
  */
 static int select_have_broken_poll(void)
 {
-    int poll_test;
     int filedes[2];
-
+    struct utsname u;
     struct pollfd poll_struct = { 0, POLLIN|POLLPRI|POLLOUT, 0 };
+    int res;
+    const char *release;
+
+    res = uname(&u);
+    if (res < 0) {
+        /* unlikely uname() failure: disable poll() */
+        return 1;
+    }
+
+    release = u.release;
+    /* bpo-28087: macOS 16.0.x-16.5.x has a broken poll().
+     * poll() with no file descriptors registered returns immediately,
+     * regardless of the timeout. */
+    if (strncmp(release, "16.", 3) == 0
+       && '0' <= release[3] && release[3] <= '5'
+       && release[4] == '.') {
+        return 1;
+    }
 
     /* Create a file descriptor to make invalid */
     if (pipe(filedes) < 0) {
@@ -1194,10 +1214,12 @@ static int select_have_broken_poll(void)
     poll_struct.fd = filedes[0];
     close(filedes[0]);
     close(filedes[1]);
-    poll_test = poll(&poll_struct, 1, 0);
-    if (poll_test < 0) {
+
+    res = poll(&poll_struct, 1, 0);
+    if (res < 0) {
         return 1;
-    } else if (poll_test == 0 && poll_struct.revents != POLLNVAL) {
+    }
+    else if (res == 0 && poll_struct.revents != POLLNVAL) {
         return 1;
     }
     return 0;
