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Remove redundant messaging #218

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@matejak matejak commented Oct 11, 2022

The send_ready already performs what the removed call could aim to accomplish.

Sending those two messages in a quick succession can lead to crashes of Anaconda.

The send_ready already performs what the removed call
could aim to accomplish.
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matejak commented Oct 11, 2022

@poncovka could you please be so kind and check it out? We suffer from crashes on RHEL8 and RHEL9 as well, would this fix be applicable on those platforms?

@matejak matejak added port-RHEL8 Port this PR to the rhel8-branch port-RHEL9 Port this PR to the rhel9-branch labels Oct 11, 2022
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When the redundant messaging happens? What steps should I perform to trigger it and reproduce? What steps do you perform to test this PR?

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matejak commented Oct 13, 2022

Sorry for omitting the BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2000998

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Hi, this fix seems to be harmless and should be applied in any case. However, I think it just lowering the probability of the error. It doesn't fix it.

What (I think) happens:

  • The Fetch button is clicked.
  • An OSCAPguiWaitForDataFetchThread thread is created.
  • Later the thread sets self._fetching to False and runs the code from the set_ready decorator.
  • The Fetch button is clicked again.
  • Since self._fetching is False, a new thread will be created.
  • However, the previous thread can still run at this point.
  • In that case, Anaconda will raise the "a thread with the same name already running" error.

My theory: When you removed a command from the set_ready decorator, the window between setting self._fetching to False and actually stopping the thread became smaller and harder to hit. If you put there some sleep, it should start to happen again.

Suggested fix:

  • Remove self._fetching and self._fetch_flag_lock.
  • Use threadMgr.get to check if there is some fetching going on.
if threadMgr.get('OSCAPguiWaitForDataFetchThread'):
   # Fetching in progress.
   ...

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matejak commented Oct 13, 2022

Thanks for the analysis, so in another words the thread doesn't end right after the _fetching is set to False, but it is guaranteed that if a thread of a known name exists, we are still fetching stuff.
I would drop the _fetching only as a part of a larger-scale refactoring, as touching these things without being aware of the full picture basically is asking for trouble, but extending the definition of "not fetching at the moment" seems as a really good, and perfectly doable idea.

It is not completely practical to rely on locks alone,
and we can elliminate some corner cases by looking
whether well-known UI threads exist.
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The inspection completed: 1 updated code elements

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Thanks for the analysis, so in another words the thread doesn't end right after the _fetching is set to False, but it is guaranteed that if a thread of a known name exists, we are still fetching stuff. I would drop the _fetching only as a part of a larger-scale refactoring, as touching these things without being aware of the full picture basically is asking for trouble, but extending the definition of "not fetching at the moment" seems as a really good, and perfectly doable idea.

I think it could prevent more issues in the future, but that's up to you. Looks good to me!

@matejak matejak removed the port-RHEL8 Port this PR to the rhel8-branch label Oct 17, 2022
@matejak matejak mentioned this pull request Nov 8, 2022
@matejak matejak removed the port-RHEL9 Port this PR to the rhel9-branch label Nov 8, 2022
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4 participants