Message 154330 - Python tracker (original) (raw)

""" Thread 0x00002ba588709700: File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/support.py", line 1168 in consumer File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/threading.py", line 682 in run File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/threading.py", line 729 in _bootstrap_inner File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/threading.py", line 702 in _bootstrap

Current thread 0x00002ba57b2d4260: File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/support.py", line 1198 in stop File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/support.py", line 1240 in wrapper File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/case.py", line 385 in _executeTestPart File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/case.py", line 440 in run File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/case.py", line 492 in call File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/suite.py", line 105 in run File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/suite.py", line 67 in call File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/suite.py", line 105 in run File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/suite.py", line 67 in call File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/unittest/runner.py", line 168 in run File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/support.py", line 1369 in _run_suite File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/support.py", line 1403 in run_unittest File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/test_bigmem.py", line 1252 in test_main File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/regrtest.py", line 1221 in runtest_inner File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/regrtest.py", line 907 in runtest File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/regrtest.py", line 710 in main File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/test/main.py", line 13 in File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/runpy.py", line 73 in _run_code File "/var/tmpfs/martin.vonloewis/3.x.loewis-parallel2/build/Lib/runpy.py", line 160 in _run_module_as_main """

There's a problem with the _file_watchdog thread: if the pipe gets full (because the consumer thread doesn't get to run often enough), the watchdog thread will block on the write() to the pipe. Then, the main thread tries to stop the watchdog:

""" static void cancel_file_watchdog(void) { /* Notify cancellation */ PyThread_release_lock(watchdog.cancel_event);

/* Wait for thread to join */
PyThread_acquire_lock(watchdog.running, 1);
PyThread_release_lock(watchdog.running);

/* The main thread should always hold the cancel_event lock */
PyThread_acquire_lock(watchdog.cancel_event, 1);

} """

The cancel_event lock is released, but the watchdog thread is stuck on the write(). The only thing that could wake it up is a read() from the consumer thread, but the main thread - the one calling cancel_file_watchdog()

""" /* We can't do anything if the consumer is too slow, just bail out */ if (write(watchdog.wfd, (void *) &x, sizeof(x)) < sizeof(x)) break; if (write(watchdog.wfd, data, data_len) < data_len) break; """

AFAICT, this can't happen, because the write end of the pipe is not in non-blocking mode (which would solve this issue).

Otherwise, there are two things I don't understand:

  1. IIUC, the goal of the watchdog thread is to collect memory consumption in a timely manner: that's now the case, but since the information is printed in a standard thread, it doesn't bring any improvement (because it can be delayed for arbitrarily long), or am I missing something?
  2. instead of using a thread and the faulthandler infrastructure to run GIL-less, why not simply use a subprocess? It could then simply parse /proc//statm at a regular interval, and print stats to stdout. It would also solve point 1.