Building the Linux Kernel on one machine, deploying on another

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Software Development flow is an elusive beast, easily frightened away. The easiest way to lose the flow is to have a long development cycle. Building the entire Linux Kernel takes time. If you are developing a single driver that can be built as a stand alone module, you do not want to have to rebuild the entire Kernel each time you make a change to that module. If that module crashes the machine when it runs into an error, you do not want to have to wait for that machine to reboot before digging in to the debugging process.

These two guidelines lead to a pattern of building on one machine and deploying on another. Here is one way to go about this process.

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Long Refactoring: Resetting the class model

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With the inclusion of the Generators, the main functions seem to be in the right shape. What seems off is the naming of things. For example, we have a couple functions that take a parameter named “board” but it turns out they mean different things. The names of classes do not seem to align with what they are doing.

Lets continue with the renaming of things and see where it leads us.

But first: we can remove the exceptions to the flake8 testing, and, with the removal of some white space, we can run with all the pep8 rules intact. Now, on to renaming.

I am not going to go through each commit, but will try to provide enough context so you could follow the logic in the commits in github.

This is the last article in my Long Refactoring series. You can read the first article here.

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Long Refactoring: Generators

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While the main solving function is now cleaned up, I am not very happy with the code that checks the validation on each cell.

I am not going to go through each step here, as the pattern is well established now. Pull out of the function anything that is a distractor. Once you have the heart of the algorithm, clean it up. Then put things back together.

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Getting a File from gitlab using a TOKEN

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I work on a system in our lab that I connect to via SSH. Fetching a file via the web and pushing it to this machine is quite slow, and I want to pull on this machine directly. The trick to make this work is to use a TOKEN from gitlab and oauth2 as the username portion of the URL. For example

curl -O   https://oauth2:$CI_JOB_TOKEN@gitlab.com/api/v4/projects/$PROJECT_ID/packages/generic/$PROJECT_NAME/$PROJECT_VERSION/$FILE

The CI_JOB_TOKEN must be set to a token that has appropriate permissions on your project. Most of the values I wrote as envvars could be copy-pasted from the gitlab packages link on the web.

Adding stable to a blobless clone

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We regularly sync various git repos from upstream to our company speicfic Linux repository. However, sometimes when working on a development machine, I need a branch from stable that we have not synced yet. If I did a blobless clone from our repository, doing a fetch from stable is going to pull over lots of blobs that I do not need.

Instead, I want to fetch just a specific tag. I can do this by adding the tag to the fetch command, and it will pull over only those blobs

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Long Refactoring: Backtracking

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Now that I have cleaned the loop up somewhat, we can continue with the process of refactoring the code. This is a continuation to the article series I started here.

This next step really moves beyond refactoring. I have identified that the intended backtracking was not actually implemented in the code. Instead, The whole board is wiped and restarted many times, causing a decent slowdown in execution. My refactoring process thus far has allowed me to understand the code well enough to attempt and improvement.

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Long Refactoring: More loop cleanup

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In my last article on the Long Refactoring series, I elided the process I went through to solve the bug. While preparing to turn the articles into a presentation, I went through the steps myself again, and came across the bug. When I was writing the articles, I was pressed for time, and didn’t go through the process of solving it step by step, which in turn means there is a gap between the pre-and-post states of the code: you can’t get there from here.
Let me take it from where I mentioned that I found a bug, and added the unit test that shows it.

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