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We need to check the exit code of each joined process in the `run_tasks()` function in `multi_proc.py`. A non-zero exit status (especially a negative exit status) indicates that an error occurred, and it is possible that the output queue (`out_q`) will be empty. Not handling this situation properly, will cause `out_q.get()` (a few lines further) to hang.
tammojan
approved these changes
May 6, 2025
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Bug description
A deadlock may occur in the function
run_tasks()inmulti_proc.py, ifout_qis empty. This may happen, if one or more of the started processes die unexpectedly.Solution
There are two ways to resolve this problem:
out_qand check if it's empty. If so, some results are apparently missing.In both cases an exception should be raised. The second solution has the advantage that you can more easily access the exit code of the first process that died, and use it in the exception message. This MR therefore implements the second solution.
How to test
To test that this solution works, make sure that one of the underlying processes die with a
SIGSEGV. This can, for example, be accomplished by reverting this change insrc/c++/MGFunction1.cc. Doing so, will raise aSIGSEGVat runtime, when the software is compiled and run with Numpy 2.x.Note
Building the software with Numpy 2.x is not trivial, because on most host systems, all packages are still compiled against Numpy 1.x. Follow the approach used in the CI pipeline https://github.com/lofar-astron/PyBDSF/blob/master/.github/workflows/ci.yml to build the software in a clean docker container.
It may be easier to just raise a signal in the aforementioned C++ file, instead of triggering the
SIGSEGVthrough the incorrect call of a Numpy function (because that requires Numpy 2.x for building the software). The software can then be built on the host system. Just raising the signal should yield the same effect.