parking_lot
linux
parking_lot | linux | |
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7 | 983 | |
2,546 | 171,387 | |
- | - | |
7.2 | 10.0 | |
18 days ago | about 3 hours ago | |
Rust | C | |
Apache License 2.0 | GNU General Public License v3.0 or later |
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parking_lot
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How fair should an unfair mutex be?
Recently I've been developing my own mutex using a lot of inspiration from the excellent parking_lot crate. The mutex in parking_lot is eventually fair in that it occasionally does a fair unlock to ensure threads aren't completely starved.
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Which Mutex to use in this case (independent tasks, partially under contention)
parking_lot still has an open issue #201: Heavily degraded performance while in extreme contention on some processors which reveals that parking_lot selfishly uses spinning locks under some circumstances to sacriice total system efficiency in the name of trying to improve its own latency. In my opinion, the only place spinning locks are excusable is fullscreen games and, even then, Linus Torvalds is of the opinion they're usually implemented wrong. (Issue 201 also includes a bunch of benchmark runs if you want to read through to figure out which one applies to the current shipping state of the codebase.)
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Why Rust mutexes look like they do
I think there was at some point the plan to make it the std implementation. However, cross platform support was kinda tricky if I remember link to an issue. I tend to suggest to always first prototype with std primitives. Often your bottlenecks are in totally different places. For example, you wait on some data C that also waits on data B but this depends on A which is a really slow query to a database.
- How to call RawRwLock.lock_exclusive() of parking_lot?
- Parking_lot: Compact and efficient synchronization primitives for Rust
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A Firehose of Rust, for busy people who know some C++
I think the current state-of-the-art in terms of high-performance, general-purpose mutexes is parking_lot. (Which was ported from a C++ project of the same name.) Rather than initializing a new underlying pthread_mutex for every instance of Mutex, it keeps a global collection of thread parking queues somewhere, which turns out to be more efficient in various ways. An individual parking_lot::Mutex doesn't require a heap allocation, and is just 1 byte in size (plus the size of T).
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Eliminating Data Races in C++ and Rust with Thread Sanitizer in Firefox – A Technical Report
The first was bug 1674770, which was a bug in the parking_lot library. This Rust library provides synchronization primitives and other concurrency tools and is written and maintained by experts. We did not investigate the impact but the issue was a couple atomic orderings being too weak and was fixed quickly by the authors. This is yet another example that proves how difficult it is to write bug-free concurrent code.
linux
- Doyensec – OOB memory read in Linux kernel
- Memory is cheap, new structs are a pain
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The File Filesystem
FFS predates FreeBSD and is in some capacity supported by all 3 major BSDs. I'm fairly confident that Linux actually supports it through the ufs driver ( https://github.com/torvalds/linux/tree/master/fs/ufs ); whether the use of different names in different places makes it better or worse is an exercise for the reader.
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Linus Torvalds adds arbitrary tabs to kernel code
These are a bit easier to see what's going on:
https://github.com/torvalds/linux/commit/d5cf50dafc9dd5faa1e...
https://github.com/torvalds/linux/blob/d5cf50dafc9dd5faa1e61...
Unfortunately Github doesn't have a way to render symbols for whitespace, but you can tell by selecting the spaces that the previous version had leading tabs. Linus changed it so that the tokens `default` and the number e.g. `12` are also separated by a tab. This is tricky, because the token "default" is seven characters, it will always give this added tab a width of 1 char which makes it always layout the same as if it were a space no matter if you use tab widths of 1, 2, 4, or 8.
- Show HN: Running TempleOS in user space without virtualization
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PfSense Software Embraces Change: A Strategic Migration to the Linux Kernel
There was also a Gentoo effort to run atop FreeBSD[0]. The challenge of course is that afaik none of the BSD kernel ABIs are considered stable. The stable interface is the BSD libc. That said, with binfmt_misc, I don't see a reason you couldn't just run (at least some) FreeBSD binaries on Linux with a thin syscall translation layer (rather something like qemu-system) and then your layer hooked via binfmt_misc. I'm not aware of anyone who has done this for FreeBSD, but prior efforts existed as alternate binfmts for SysVr4/5 ELF binaries[2]. Either way would take some elbow grease, but you *might* even be able just reuse binfmt_elf and just have a new interpreter for FreeBSD elf.
[0] https://wiki.gentoo.org/wiki/Gentoo_FreeBSD
[1] https://docs.kernel.org/admin-guide/binfmt-misc.html
[2] https://github.com/torvalds/linux/blob/master/fs/binfmt_elf....
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Improvements to static analysis in GCC 14
> The original less-than check was deemed incorrect
It was only deemed incorrect because of an information leak. Not because it's a valid use-case for user space to copy smaller portions of *hwrpb into user space. https://github.com/torvalds/linux/commit/21c5977a836e399fc71...
- Linus Torvalds accepts a merge commit to the Linux kernel
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TinyMCE (also) moving from MIT to GPL
Correct. And the combined work needs to carry the MIT license text and copyright attributions for the MIT software authors. With binary distribution it must also be overt, not hidden in some source code drop, but directly accompanying the binary.
Many people who talk about relicensing never credit the MIT developers or distribute the MIT license text. "Because it's GPL now."
I don't think that you believe that, but many developers do.
Some don't see the need for source code scans for Open Source compliance, because the license.txt says GPL, so it's GPL. Prime example is the Linux kernel. There is code under different licenses in there, but people don't even read https://github.com/torvalds/linux/blob/master/COPYING till the end ("In addition, other licenses may also apply.") and conclude it's simply GPL 2 and nothing else.
Also be aware that sublicensing is not the same as relicensing.
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Linus Torvalds is looking for a more modern GUI editor
> Does he have something against it?
He notoriously hates GNU Emacs, yes.
https://marc.info/?m=122955159617722
https://github.com/torvalds/linux/blob/master/Documentation/...
What are some alternatives?
cs_libguarded - Header-only library for multithreaded programming
zen-kernel - Zen Patched Kernel Sources
DS4Windows - Like those other ds4tools, but sexier
winapps - Run Windows apps such as Microsoft Office/Adobe in Linux (Ubuntu/Fedora) and GNOME/KDE as if they were a part of the native OS, including Nautilus integration.
Open and cheap DIY IP-KVM based on Raspberry Pi - Open and inexpensive DIY IP-KVM based on Raspberry Pi
serenity - The Serenity Operating System 🐞
DsHidMini - Virtual HID Mini-user-mode-driver for Sony DualShock 3 Controllers
RyzenAdj - Adjust power management settings for Ryzen APUs
edk2-sdm845 - (Maybe) Generic edk2 port for sdm845
void-packages - The Void source packages collection
illumos-gate - An open-source Unix operating system
vscode-gitlens - Supercharge Git inside VS Code and unlock untapped knowledge within each repository — Visualize code authorship at a glance via Git blame annotations and CodeLens, seamlessly navigate and explore Git repositories, gain valuable insights via rich visualizations and powerful comparison commands, and so much more