`test.test_ssl.ThreadedTests.test_sendfile` times out on i686 build of 3.15.0a1 in Fedora

Bug report

Bug description:

On Fedora Linux 44, the built i686 debug Python 3.15.0a1 fails the test.regrtest, as test_sendfile times out:

test_sendfile (test.test_ssl.ThreadedTests.test_sendfile)
Try to send a file using kTLS if possible. ... kTLS is available
Timeout (0:45:00)!
Thread 0xf1effb40 [Thread-221] (most recent call first):
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/ssl.py", line 1155 in read
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/test_ssl.py", line 2484 in read
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/test_ssl.py", line 2507 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/threading.py", line 1075 in _bootstrap_inner
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/threading.py", line 1037 in _bootstrap
Thread 0xf16feb40 [Thread-220] (most recent call first):
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/threading.py", line 1126 in join
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/test_ssl.py", line 2673 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/threading.py", line 1075 in _bootstrap_inner
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/threading.py", line 1037 in _bootstrap
Thread 0xf7585700 [python] (most recent call first):
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/ssl.py", line 1155 in read
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/ssl.py", line 1335 in recv
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/test_ssl.py", line 4603 in test_sendfile
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/case.py", line 613 in _callTestMethod
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/case.py", line 667 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/case.py", line 723 in __call__
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/suite.py", line 122 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/suite.py", line 84 in __call__
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/suite.py", line 122 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/suite.py", line 84 in __call__
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/unittest/runner.py", line 257 in run
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 84 in _run_suite
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 42 in run_unittest
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 162 in test_func
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 118 in regrtest_runner
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 165 in _load_run_test
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 210 in _runtest_env_changed_exc
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 319 in _runtest
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/single.py", line 348 in run_single_test
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/worker.py", line 92 in worker_process
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/worker.py", line 127 in main
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/test/libregrtest/worker.py", line 131 in <module>
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/runpy.py", line 88 in _run_code
  File "/builddir/build/BUILD/python3.15-3.15.0_a1-build/Python-3.15.0a1/Lib/runpy.py", line 198 in _run_module_as_main
1 test failed again:
    test_ssl

CPython versions tested on:

3.15

Operating systems tested on:

Linux

从 Lib/test/test_ssl.py 开始，尤其关注 ThreadedTests.test_sendfile 及其 read/run 辅助函数，并在 Fedora i686 debug build 上复现 test_ssl。阅读超时信息中显示的对应 Lib/ssl.py read 和 recv 路径；完成的标准是 test_sendfile 在受影响的配置上不发生超时并完成。