ARM Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life (Terry Pratchett, Jingo)

[$] The many faces of "latency nice"

([Kernel] May 18, 2020 18:52 UTC (Mon) (corbet))

A task's "nice" value describes its priority within the completely fair scheduler; its semantics have roots in ancient Unix tradition. Last August, a [1]"latency nice" parameter was proposed to provide similar control over a task's response-time requirements. At the 2020 [2]Power Management and Scheduling in the Linux Kernel summit (OSPM), Parth Shah, Chris Hyser, and Dietmar Eggemann ran a discussion about the latency nice proposal; it seems that everybody agrees that it would be a useful feature to have, but there is a wide variety of opinions about what it should actually do.



[1] https://lwn.net/ml/linux-kernel/20190830174944.21741-1-subhra.mazumdar@oracle.com/

[2] http://retis.sssup.it/ospm-summit/

Security updates for Friday

([Security] May 15, 2020 14:56 UTC (Fri) (jake))

Security updates have been issued by Debian (apt, inetutils, and log4net), Fedora (kernel, mailman, and viewvc), Gentoo (chromium, freerdp, libmicrodns, live, openslp, python, vlc, and xen), Oracle (.NET Core, container-tools:1.0, and kernel), Red Hat (kernel-rt), Scientific Linux (kernel), SUSE (kernel, libvirt, python-PyYAML, and syslog-ng), and Ubuntu (json-c).

Five years of Rust

([Development] May 15, 2020 12:48 UTC (Fri) (corbet))

It seems that the Rust programming language [1]has only been around for five years . " With all that's going on in the world you'd be forgiven for forgetting that as of today, it has been five years since we released 1.0 in 2015! Rust has changed a lot these past five years, so we wanted reflect back on all of our contributors' work since the stabilization of the language. "



[1] https://blog.rust-lang.org/2020/05/15/five-years-of-rust.html

Going above and beyond with Inkscape 1.0 (Libre Graphics World)

([Development] May 15, 2020 12:39 UTC (Fri) (corbet))

Libre Graphics World is running [1]an extensive interview with several Inkscape developers. " I'd say we're at the point of supporting SVG as much as possible, but we've mostly given up trying to add editing features to the SVG specification. As the W3C is dominated by web browsers who don't need multi page or connectors. I dare not say much more about W3C-specific things. I know that I'm personally disappointed that Inkscape's considerable importance in the SVG creation space does not lend itself to getting the feature we intend to build into Inkscape into the actual SVG specification. This does lead to the problem that going forwards we're likely to have browser incompatibilities. "



[1] http://libregraphicsworld.org/blog/entry/going-above-and-beyond-with-inkscape-1-0

[$] Utilization inversion and proxy execution

([Kernel] May 15, 2020 17:20 UTC (Fri) (corbet))

Over the years, the kernel's CPU scheduler has become increasingly aware of how much load every task is putting on the system; this information is used to make smarter task placement decisions. Sometimes, though, this logic can go wrong, leading to a situation that Valentin Schneider describes as "utilization inversion". At the 2020 [1]Power Management and Scheduling in the Linux Kernel summit (OSPM), he described the problem and some approaches that are being considered to address it.



[1] http://retis.sssup.it/ospm-summit/

[$] Testing scheduler thermal properties for avionics

([Kernel] May 15, 2020 16:00 UTC (Fri) (corbet))

Linux is not heavily used in safety-critical systems — yet. There is an increasing level of interest in such deployments, though, and that is driving a number of initiatives to determine how Linux can be made suitable for safety-critical environments. At the 2020 [1]Power Management and Scheduling in the Linux Kernel summit (OSPM), Michal Sojka shone a light on one corner of this work: testing the thermal characteristics of Linux systems with an eye toward deployment in avionics systems.



[1] http://retis.sssup.it/ospm-summit/

LWN.net Weekly Edition for May 21, 2020


Three new stable kernels

([Kernel] May 14, 2020 13:45 UTC (Thu) (jake))

The [1]5.6.13 , [2]5.4.41 , and [3]4.19.123 stable kernels have been released. They contain important fixes throughout the kernel tree; users should upgrade.



[1] https://lwn.net/Articles/820523/

[2] https://lwn.net/Articles/820524/

[3] https://lwn.net/Articles/820527/

Security updates for Thursday

([Security] May 14, 2020 12:46 UTC (Thu) (jake))

Security updates have been issued by Debian (apt and libreswan), Fedora (glpi, grafana, java-latest-openjdk, mailman, and oddjob), Oracle (container-tools:2.0, container-tools:ol8, kernel, libreswan, squid:4, and thunderbird), SUSE (apache2, grafana, and python-paramiko), and Ubuntu (apt and libexif).

[$] The weighted TEO cpuidle governor

([Kernel] May 14, 2020 16:43 UTC (Thu) (corbet))

Life gets complicated for the kernel when there is nothing for the system to do. The obvious response is to put the CPU into an idle state to save power, but which one? CPUs offer a wide range of sleep states with different power-usage and latency characteristics. Picking too shallow a state will waste energy, while going too deep hurts latency and can impact the performance of the system as a whole. The [1]timer-events-oriented (TEO) cpuidle governor is a relatively new attempt to improve the kernel's choice of sleep states; at the 2020 [2]Power Management and Scheduling in the Linux Kernel Summit , Pratik Sampat presented [3]a variant of the TEO governor that tries to improve its choices further.



[1] https://lwn.net/Articles/775618/

[2] http://retis.sssup.it/ospm-summit/

[3] https://lwn.net/ml/linux-kernel/20200511141055.43029-2-psampat@linux.ibm.com/

[$] Subinterpreters for Python

([Development] May 13, 2020 20:17 UTC (Wed) (jake))

A project that has been floating around in the Python world for a number of years is now working its way toward inclusion into the language—or not. "Subinterpreters", which are separate Python interpreters that can currently be created via the C API for extensions, are seen by some as a way to get a more Go-like concurrency model for Python. The first step toward that goal is to expose that API in the standard library. But there are questions about whether subinterpreters are actually a desirable feature for Python at all, as well as whether the hoped-for concurrency improvements will materialize.

Security updates for Wednesday

([Security] May 13, 2020 14:59 UTC (Wed) (ris))

Security updates have been issued by Fedora (java-1.8.0-openjdk and seamonkey), Gentoo (firefox, lrzip, qemu, squid, and thunderbird), Oracle (thunderbird), Red Hat (buildah, kernel, kernel-alt, kernel-rt, kpatch-patch, podman, python-pip, python-virtualenv, and qemu-kvm), Scientific Linux (kernel), Slackware (mariadb), SUSE (openconnect), and Ubuntu (file, firefox, iproute2, pulseaudio, and squid, squid3).

[$] Completing and merging core scheduling

([Kernel] May 13, 2020 16:19 UTC (Wed) (corbet))

[1]Core scheduling is a proposed modification to the kernel's CPU scheduler that allows system administrators to control which processes can be running simultaneously on the same processor core. It was originally proposed as a security mechanism, but [2]other use cases have shown up over time as well. At the 2020 [3]Power Management and Scheduling in the Linux Kernel summit (OSPM), a group of some 50 developers gathered online to discuss the current state of the core-scheduling patches and what is needed to get them into the mainline kernel.



[1] https://lwn.net/Articles/780703/

[2] https://lwn.net/Articles/799454/

[3] http://retis.sssup.it/ospm-summit/

Security updates for Tuesday

([Security] May 12, 2020 14:57 UTC (Tue) (ris))

Security updates have been issued by Arch Linux (a2ps and qutebrowser), openSUSE (cacti, cacti-spine, ghostscript, and python-markdown2), Oracle (kernel), Red Hat (chromium-browser, libreswan, and qemu-kvm-ma), Scientific Linux (thunderbird), and SUSE (kernel and libvirt).

Hussain: Lord of the io_uring

([Kernel] May 11, 2020 19:49 UTC (Mon) (corbet))

Shuveb Hussain has posted [1]an extensive introduction to io_uring , complete with examples and a reference guide. " Because of the shared ring buffers between the kernel and user space, io_uring can be a zero-copy system. Copying bytes around becomes necessary when there are system calls that transfer data between kernel and user space are involved. But since the bulk of the communication in io_uring is via buffers shared between the kernel and user space, this huge performance overhead is completely avoided. "



[1] https://unixism.net/loti/

[$] What's coming in Go 1.15

([Development] May 12, 2020 18:12 UTC (Tue) (benhoyt))

Go 1.15, the 16th major version of the [1]Go programming language , is due out on August 1. It will be a release with fewer changes than usual, but many of the major changes are behind-the-scenes or in the tooling: for example, there is a new linker, which will speed up build times and reduce the size of binaries. In addition, there are performance improvements to the language's runtime, changes to the architectures supported, and some updates to the standard library. Overall, it should be a solid upgrade for the language.



[1] https://golang.org/

A set of stable kernels

([Kernel] May 11, 2020 15:15 UTC (Mon) (ris))

Stable kernels [1]5.6.12 , [2]5.4.40 , [3]4.19.122 , [4]4.14.180 , [5]4.9.223 , and [6]4.4.223 have been released. They all contain important fixes and users should upgrade.



[1] https://lwn.net/Articles/820198/

[2] https://lwn.net/Articles/820199/

[3] https://lwn.net/Articles/820200/

[4] https://lwn.net/Articles/820201/

[5] https://lwn.net/Articles/820202/

[6] https://lwn.net/Articles/820203/

Security updates for Monday

([Security] May 11, 2020 15:04 UTC (Mon) (ris))

Security updates have been issued by Arch Linux (chromium and firefox), Debian (libntlm, squid, thunderbird, and wordpress), Fedora (chromium, community-mysql, crawl, roundcubemail, and xen), Mageia (chromium-browser-stable), openSUSE (chromium, firefox, LibVNCServer, openldap2, opera, ovmf, php7, python-PyYAML, rpmlint, rubygem-actionview-5_1, slirp4netns, sqliteodbc, squid, thunderbird, and webkit2gtk3), Oracle (firefox, git, gnutls, kernel, libvirt, squid, and targetcli), Red Hat (thunderbird), SUSE (firefox, squid, and thunderbird), and Ubuntu (mailman).

Kernel prepatch 5.7-rc5

([Kernel] May 10, 2020 22:47 UTC (Sun) (corbet))

The [1]5.7-rc5 kernel prepatch is out for testing. " We'll see what the next few weeks bring, but at least for now it all feels normal, and like the 5.7 release is tracking well. So please keep testing, and if you haven't dared a 5.7 pre-release kernel yet, we're well into the 'things look calm and safe to test' time. "



[1] https://lwn.net/Articles/820119/

[$] O_MAYEXEC — explicitly opening files for execution

([Kernel] May 11, 2020 18:55 UTC (Mon) (corbet))

Normally, when a kernel developer shows up with a proposed option that doesn't do anything, a skeptical response can be expected. But there are exceptions. Mickaël Salaün is [1]proposing the addition of a new flag ( O_MAYEXEC ) for the [2]openat2() system call that, by default, will change nothing. But it does open a path toward tighter security in some situations.



[1] https://lwn.net/ml/linux-kernel/20200505153156.925111-1-mic@digikod.net/

[2] http://man7.org/linux/man-pages/man2/openat2.2.html
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