Linux Kernel: Latest Articles in LWN and Linux Display Next Hackfest in A Coruña
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LWN
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LWN ☛ The state of realtime and embedded Linux
Linux, famously, appears in a wide range of systems. While servers and large data centers get a lot of the attention, and this year will always be the year of the Linux desktop, there is also a great deal of Linux to be found in realtime and embedded applications. Two talks held in the realtime and embedded tracks of the 2024 Open Source Summit North America provided listeners with an update on how Linux is doing in those areas. Work on realtime Linux appears to be nearing completion, while the embedded community is still pushing forward at full speed.
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The realtime session was run as a panel discussion featuring Kate Stewart, Daniel Bristot de Oliveira, Sebastian Siewior, and an empty chair representing Thomas Gleixner who, with help from the airlines, missed his deadline for arrival to the conference. Bristot started by asking what has motivated the realtime community to do all of the work it has done. Stewart answered that there was a problem (the need for a version of Linux that could meet realtime response requirements), and a number of companies got together to fund it. The latest stage alone was an eight-year journey, but this project is getting close to completion.
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LWN ☛ Support for the TSO memory model on Arm CPUs
At the CPU level, a memory model describes, among other things, the amount of freedom the processor has to reorder memory operations. If low-level code does not take the memory model into account, unpleasant surprises are likely to follow. Naturally, different CPUs offer different memory models, complicating the portability of certain types of concurrent software. To make life easier, some Arm CPUs offer the ability to emulate the x86 memory model, but efforts to make that feature available in the kernel are running into opposition.
CPU designers will do everything they can to improve performance. With regard to memory accesses, "everything" can include caching operations, executing them out of order, combining multiple operations into one, and more. These optimizations do not affect a single CPU running in isolation, but they can cause memory operations to be visible to other CPUs in a surprising order. Unwary software running elsewhere in the system may see memory operations in an order different from what might be expected from reading the code; this article describes one simple scenario for how things can go wrong, and this series on lockless algorithms shows in detail some of the techniques that can be used to avoid problems related to memory ordering.
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LWN ☛ Giving Rust a chance for in-kernel codecs
Video playback is undeniably one of the most important features in modern consumer devices. Yet, surprisingly, users are by and large unaware of the intricate engineering involved in the compression and decompression of video data, with codecs being left to find a delicate balance between image quality, bandwidth, and power consumption. In response to constant performance pressure, video codecs have become complex and hardware implementations are now common, but programming these devices is becoming increasingly difficult and fraught with opportunities for exploitation. I hope to convey how Rust can help fix this problem.
Some time ago, I proposed to the Linux media community that, since codec data is particularly sensitive, complex, and hard to parse, we could write some of the codec drivers in Rust to benefit from its safety guarantees. Some important concerns were raised back then, in particular that having to maintain a Rust abstraction layer would impose a high cost on the already overstretched maintainers. So I went back to the drawing board and came up with a new, simpler proposal; it differs a bit from the general flow of the Rust-for-Linux community so far by realizing that we can convert error-prone driver sections without writing a whole layer of Rust bindings.
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Graphics Stack
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Melissa Wen: Get Ready to 2024 Linux Display Next Hackfest in A Coruña!
We’re excited to announce the details of our upcoming 2024 GNU/Linux Display Next Hackfest in the beautiful city of A Coruña, Spain!
This year’s hackfest will be hosted by Igalia and will take place from May 14th to 16th. It will be a gathering of minds from a diverse range of companies and open source projects, all coming together to share, learn, and collaborate outside the traditional conference format.
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