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Programming Leftovers

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  • Stupid RCU Tricks: Torturing RCU Fundamentally, Part I

    A quick look at the beginning of the Documentation/RCU/Design/Requirements/Requirements.rst file in a recent Linux-kernel source tree might suggest that testing RCU's fundamental requirements is Job One. And that suggestion would be quite correct. This post describes how rcutorture tests RCU's grace-period guarantee, which is usually used to make sure that data is not freed out from under an RCU reader. Later posts will describe how the other fundamental guarantees are tested.


    The rcu_torture_removed list is handled by the rcu_torture_pipe_update_one() function that is invoked by rcutorture callbacks and the rcu_torture_pipe_update() function that is invoked by rcu_torture_writer() after completing a synchronous RCU grace period. The rcu_torture_pipe_update_one() function updates only the specified array element, and the rcu_torture_pipe_update() function updates all of the array elements residing on the rcu_torture_removed list. These updates each increment the -&gtrtort_pipe_count field. When the value of this field reaches RCU_TORTURE_PIPE_LEN (by default 10), the array element is freed for reuse.

    The rcu_torture_reader() function handles the random time delays and leverages the awesome power of multiple kthreads to maintain a high read-side load on RCU. The rcu_torture_writer() function runs in a single kthread in order to simplify synchronization, but it enlists the help of several other kthreads repeatedly invoking the rcu_torture_fakewriter() in order to keep the update-side load on RCU at a respectable level.

  • Jonathan Dowland: Type design

    For some recent work I needed to define some additional properties for the operators: properties that would be used in a M/M/1 model (Jackson network) to represent the program do some cost modelling with. Initially we supplied this additional information in completely separate instances of types: e.g. lists of tuples, the first of a pair representing a vertexID, etc. This was mostly fine for totally novel code, but where I had existing code paths that operated in terms of Graph StreamVertex and now needed access to these parameters, it would have meant refactoring a lot of code. So instead, I added these properties directly to the types above.

  • What do I use to release a module to CPAN for the first time?

    Several months ago I read a tutorial on module creation. It got me thinking about releasing some of my modules. I got to work getting my code organized. At the time I had all of my work in the directory for my site. So I moved my general purpose modules to their own directory and then started reading more about what is needed to get a module published on CPAN.

    I first installed Module::Starter. It seemed like a good place to start, but then Dist::Zilla was suggested, so I installed it. Most recently Minilla suggested, and now it is installed. The problem is, I do not know which one to use. Do I use any of those at all, or is there yet another packaging module (with executable) out there?

  • Andrew Dalke: A molfile precursor?

    I think I found a precursor to the MDL molfile in a 1973 publication by Gund, Wipke, and Langridge.


    You can see the basic structure is similar to a Molfile, though a Molfile has two additional lines for misc. info., and the counts line and the atom and bond lines all have a few more fields.

    The full citation is: Gund, P., Wipke, W. T., and Langridge, R., Computer Searching of a Molecular Structure File for Pharmacophoric Patterns, Computers in Chemical Research and Education, vol 3, pp. 33-38 (1974).

    The publication contains papers from a conference in in 1973 but Google Scholar says it was published in 1974 so I'm going with that. Also, the above quote is from the second page of the paper and the figure is at the top of the third page. The page numbers on the bottom of the pages are "5/34" and "5/35", respectively.

  • Python Bytes: #202 Jupyter is back in black!
  • The Maw of Chaos - why time forecasting is so challenging?

    I promised to myself not to write about Covid-19.

    However, with my recent inclination in going back to fundamentals and revisiting some of the more interesting topics in mathematics, I thought it would be fun and useful to explain why forecasting a time series (e.g. a disease progression) is so challenging. More precisely, I want to explain why making such simulations can be really be hard sometimes by showing how things work at the fundamental level.

    We will start with some basic equations and discuss the main challenges that relate to data and building models. Then, we will move on to a more intricate mathematical phenomenon known as chaos. Just like in Thief: The Dark Project (one of my old favorites) we will descent into it gradually, but this time, we will be equipped with python. Wink

  • Bash How to Print a Variable?

    Bash scripts are an effective means of increasing efficiency in programming. They also increase reusability to the fullest since when a Bash script is once written, can be executed for as many times as the user wants. In this article, our goal is to learn the method of printing a variable using Bash.

More in Tux Machines

digiKam 7.7.0 is released

After three months of active maintenance and another bug triage, the digiKam team is proud to present version 7.7.0 of its open source digital photo manager. See below the list of most important features coming with this release. Read more

Dilution and Misuse of the "Linux" Brand

Samsung, Red Hat to Work on Linux Drivers for Future Tech

The metaverse is expected to uproot system design as we know it, and Samsung is one of many hardware vendors re-imagining data center infrastructure in preparation for a parallel 3D world. Samsung is working on new memory technologies that provide faster bandwidth inside hardware for data to travel between CPUs, storage and other computing resources. The company also announced it was partnering with Red Hat to ensure these technologies have Linux compatibility. Read more

today's howtos

  • How to install go1.19beta on Ubuntu 22.04 – NextGenTips

    In this tutorial, we are going to explore how to install go on Ubuntu 22.04 Golang is an open-source programming language that is easy to learn and use. It is built-in concurrency and has a robust standard library. It is reliable, builds fast, and efficient software that scales fast. Its concurrency mechanisms make it easy to write programs that get the most out of multicore and networked machines, while its novel-type systems enable flexible and modular program constructions. Go compiles quickly to machine code and has the convenience of garbage collection and the power of run-time reflection. In this guide, we are going to learn how to install golang 1.19beta on Ubuntu 22.04. Go 1.19beta1 is not yet released. There is so much work in progress with all the documentation.

  • molecule test: failed to connect to bus in systemd container - openQA bites

    Ansible Molecule is a project to help you test your ansible roles. I’m using molecule for automatically testing the ansible roles of geekoops.

  • How To Install MongoDB on AlmaLinux 9 - idroot

    In this tutorial, we will show you how to install MongoDB on AlmaLinux 9. For those of you who didn’t know, MongoDB is a high-performance, highly scalable document-oriented NoSQL database. Unlike in SQL databases where data is stored in rows and columns inside tables, in MongoDB, data is structured in JSON-like format inside records which are referred to as documents. The open-source attribute of MongoDB as a database software makes it an ideal candidate for almost any database-related project. This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you the step-by-step installation of the MongoDB NoSQL database on AlmaLinux 9. You can follow the same instructions for CentOS and Rocky Linux.

  • An introduction (and how-to) to Plugin Loader for the Steam Deck. - Invidious
  • Self-host a Ghost Blog With Traefik

    Ghost is a very popular open-source content management system. Started as an alternative to WordPress and it went on to become an alternative to Substack by focusing on membership and newsletter. The creators of Ghost offer managed Pro hosting but it may not fit everyone's budget. Alternatively, you can self-host it on your own cloud servers. On Linux handbook, we already have a guide on deploying Ghost with Docker in a reverse proxy setup. Instead of Ngnix reverse proxy, you can also use another software called Traefik with Docker. It is a popular open-source cloud-native application proxy, API Gateway, Edge-router, and more. I use Traefik to secure my websites using an SSL certificate obtained from Let's Encrypt. Once deployed, Traefik can automatically manage your certificates and their renewals. In this tutorial, I'll share the necessary steps for deploying a Ghost blog with Docker and Traefik.