The linux_iouring backend appears to 'work' on bionic

src/gevent/testing/patched_tests_setup.py

@@ -1324,7 +1324,7 @@ if TRAVIS:
         'test_ssl.ContextTests.test_options',
         'test_ssl.ThreadedTests.test_alpn_protocols',
         'test_ssl.ThreadedTests.test_default_ecdh_curve',
-        'test_ssl.ThreadedTests.test_shared_ciphers,'
+        'test_ssl.ThreadedTests.test_shared_ciphers',
 
     ]
 

src/gevent/testing/sysinfo.py

@@ -176,3 +176,14 @@ def libev_supports_linux_aio():
     from platform import release
 
     return system() == 'Linux' and LooseVersion(release() or '0') >= LooseVersion('4.19')
+
+def libev_supports_linux_iouring():
+    # libev requires kernel XXX to be able to support linux io_uring.
+    # It fails with the kernel in fedora rawhide (4.19.76) but
+    # works (doesn't fail catastrophically when asked to create one)
+    # with kernel 5.3.0 (Ubuntu Bionic)
+    from distutils.version import LooseVersion
+    from platform import system
+    from platform import release
+
+    return system() == 'Linux' and LooseVersion(release() or '0') >= LooseVersion('5.3')

src/gevent/tests/test__close_backend_fd.py

@@ -32,10 +32,11 @@ class Test(unittest.TestCase):
     )
 
     BACKENDS_THAT_WILL_FAIL_TO_CREATE_AT_RUNTIME = (
-        # This fails on the Ubuntu Bionic image, and on
-        # the Fedora Rawhide 33 image. It's not clear why; needs
-        # investigated.
+        # This fails on the Fedora Rawhide 33 image. It's not clear
+        # why; needs investigated.
         'linux_iouring',
+    ) if not sysinfo.libev_supports_linux_iouring() else (
+
     )
 
     BACKENDS_THAT_WILL_FAIL_TO_CREATE_AT_RUNTIME += (