classification
Title: Thread.is_alive while running Process.is_alive causes either premature termination or never-terminating.
Type: behavior Stage:
Components: Versions: Python 3.4, Python 2.7
process
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: Hexorg
Priority: normal Keywords:

Created on 2018-12-05 12:55 by Hexorg, last changed 2018-12-05 12:55 by Hexorg.

Files
File name Uploaded Description Edit
bug_test.py Hexorg, 2018-12-05 12:55
Messages (1)
msg331106 - (view) Author: Stan (Hexorg) Date: 2018-12-05 12:55
Checking if thread.is_alive() while thread is checking on Process.is_alive() seemingly causes undefined behavior. 

The attached POC is expected to print "ThreadN.data == 1999" for N in range(0, 20) with some repeats. However the integers are spread all over the place. Moreover sometimes one or more of the threads never terminate resulting in technically infinite amount of "ThreadN.data == ###" prints. 

In python2.7.15 I never observed a thread lock (only early terminations), but in python3.4.8 I did.

You may have to adjust max_count variable to have higher success rate of thread locking. I got about 40% chance of `python3 bug_test.py` never finishing on an Intel(R) Core(TM) i7-4610M CPU @ 3.00GHz
History
Date User Action Args
2018-12-05 12:55:10Hexorgcreate