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LWN.net is a comprehensive source of news and opinions from and about the Linux community. This is the main LWN.net feed, listing all articles which are posted to the site front page.
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[$] Page pinning and filesystems

Sre, 05/11/2022 - 00:13
It would have been surprising indeed if the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM) did not include a session working toward solutions to the longstanding problems with get_user_pages(), an internal function that locks user-space pages in memory for access by the kernel. The issue has, after all, come up numerous times over the years. This year's event duly contained a session in the joint filesystem and memory-management track, led by John Hubbard, with a focus on page pinning and how it interacts with filesystems.

[$] Recent RCU changes

Tor, 05/10/2022 - 21:39
In a combined filesystem and memory-management session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Paul McKenney gave an update on the changes to the read-copy-update (RCU) subsystem that had been made over the last several years. He started with a quick overview of what RCU is and why it exists at all. He did not go into any real depth, though, since many of the topics could take a 90-minute session of their own, he said, but he did provide some descriptions of the work that has gone into RCU recently.

[$] The state of memory-management development

Tor, 05/10/2022 - 17:44
The 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM) was the first chance for Linux memory-management developers to gather in three years. In a session at the end of the first day led by maintainer Andrew Morton, those developers discussed the memory-management development process. While the overall governance will remain the same, there are nonetheless some significant changes in store for this subsystem.

Fedora 36 released

Tor, 05/10/2022 - 15:31
The Fedora 36 release is now available. Improvements include GNOME 42, Wayland support by default on systems with NVIDIA graphics, Podman 4.0, Ansible 5, the removal of support for legacy ifcfg configuration files, GCC 12, and more; see the release notes for details.

[$] Improving memory-management documentation

Tor, 05/10/2022 - 14:01
Like much of the kernel, the memory-management subsystem is under-documented, and much of the documentation that does exist is less than fully current. At the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Mike Rapoport ran a session on memory-management documentation and what can be done to improve it. The result was a reinvigorated interest in documentation, but only time will tell what actual improvements will come from that interest.

Security updates for Tuesday

Tor, 05/10/2022 - 13:33
Security updates have been issued by Debian (kicad and qemu), Fedora (thunderbird), Oracle (expat), Red Hat (samba), Slackware (kernel), and SUSE (firefox, ldb, and rsyslog).

Poettering: Fitting Everything Together

Pon, 05/09/2022 - 22:44
Lennart Poettering designs his ideal desktop operating system in great detail:

First and foremost, I think the focus must be on an image-based design rather than a package-based one. For robustness and security it is essential to operate with reproducible, immutable images that describe the OS or large parts of it in full, rather than operating always with fine-grained RPM/dpkg style packages. That's not to say that packages are not relevant (I actually think they matter a lot!), but I think they should be less of a tool for deploying code but more one of building the objects to deploy.

McQueen: Evolving a GNOME strategy for 2022 and beyond

Pon, 05/09/2022 - 22:34
Robert McQueen describes some initiatives being taken by the GNOME Foundation to attract more users and developers to the platform.

There are many different threats to free access to computing and information in today’s world. The GNOME desktop and apps need to give users convenient and reliable access to technology which works similarly to the tools they already use everyday, but keeps them and their data safe from surveillance, censorship, filtering or just being completely cut off from the Internet. We believe that we can seek both philanthropic and grant funding for this work. It will make GNOME a more appealing and comprehensive offering for the many people who want to protect their privacy.

[$] Dealing with negative dentries

Pon, 05/09/2022 - 21:35
The problem of negative dentries accumulating in the dentry cache in an unbounded manner, as we looked at back in April, came up at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). Negative dentries reflect failed file-name lookups, which are then cached, saving an expensive operation if the file name in question is looked up again. There is no mechanism to proactively prune back those cache entries, however, so the cache keeps growing until memory pressure finally causes the system to forcibly evict some of them, which can make the system unresponsive for a long time or even cause a soft lockup.

[$] Ways to reclaim unused page-table pages

Pon, 05/09/2022 - 14:38
One of the memory-management subsystem's most important jobs is reclaiming unused (or little-used) memory so that it can be put to better use. When it comes to one of the core memory-management data structures — page tables — though, this subsystem often falls down on the job. At the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), David Hildenbrand led a session on the problems posed by the lack of page-table reclaim and explored options for improving the situation.

Four new stable kernels

Pon, 05/09/2022 - 14:05
Greg Kroah-Hartman has announced the release of the 5.17.6, 5.15.38, 5.10.114, and 5.4.192 stable kernels. As usual, these contain important fixes throughout the tree; users of those series should upgrade.

Security updates for Monday

Pon, 05/09/2022 - 13:54
Security updates have been issued by CentOS (firefox and thunderbird), Debian (ecdsautils and libz-mingw-w64), Fedora (cifs-utils, firefox, galera, git, java-1.8.0-openjdk, java-11-openjdk, java-17-openjdk, java-latest-openjdk, mariadb, maven-shared-utils, mingw-freetype, redis, and seamonkey), Mageia (dcraw, firefox, lighttpd, rsyslog, ruby-nokogiri, and thunderbird), Scientific Linux (thunderbird), SUSE (giflib, kernel, and libwmf), and Ubuntu (dbus and rsyslog).

Kernel prepatch 5.18-rc6

Pon, 05/09/2022 - 01:10
The 5.18-rc6 kernel prepatch is out for testing. "Please do go test it all out - because things may look good now, but continued testing is the only thing that will make sure."

GCC 12.1 Released

Pet, 05/06/2022 - 17:52
The GCC project has made the first release of the GCC 12 series, GCC 12.1. As the announcement notes, this month is the 35th anniversary of the GCC 1.0 release. There are lots of changes and fixes in this release, including: This release deprecates support for the STABS debugging format and introduces support for the CTF debugging format. The C and C++ frontends continue to advance with extending support for features in the upcoming C2X and C++23 standards and the C++ standard library improves support for the experimental C++20 and C++23 parts. The Fortran frontend now fully supports TS 29113 for interoperability with C.

[...] On the security side GCC can now initialize stack variables implicitly using -ftrivial-auto-var-init to help tracking down and mitigating uninitialized stack variable flaws. The C and C++ frontends now support __builtin_dynamic_object_size compatible with the clang extension. The x86 backend gained mitigations against straight line speculation with -mharden-sls. The experimental Static Analyzer gained uninitialized variable use detection and many other improvements.

[$] The ongoing search for mmap_lock scalability

Pet, 05/06/2022 - 15:59
There are certain themes that recur regularly at the Linux Storage, Filesystem, Memory-Management, and BPF Summit; among the most reliable is the scalability problems posed by the mmap_lock (formerly mmap_sem) lock. This topic has come up in (at least) 2013, 2018 (twice), and 2019. The 2022 event was no exception, with three consecutive sessions led by Liam Howlett, Michel Lespinasse, and Suren Baghdasaryan dedicated to the topic. There are improvements on the horizon, but the problem is far from solved.

Security updates for Friday

Pet, 05/06/2022 - 14:34
Security updates have been issued by Debian (dpdk, mruby, openjdk-11, and smarty3), Oracle (thunderbird), Red Hat (thunderbird), SUSE (chromium, libvirt, python-Twisted, and tar), and Ubuntu (cron and jbig2dec).

[$] How to cope with hardware-poisoned page-cache pages

Čet, 05/05/2022 - 14:25
"Hardware poisoning" is a mechanism for detecting and handling memory errors in a running system. When a particular range of memory ceases to remember correctly, it is "poisoned" and further accesses to it will generate errors. The kernel has had support for hardware poisoning for over a decade, but that doesn't mean it can't be improved. At the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit, Yang Shi discussed the challenges of dealing with hardware poisoning when it affects memory used for the page cache.

Security updates for Thursday

Čet, 05/05/2022 - 14:18
Security updates have been issued by Debian (firefox-esr), Fedora (firefox, java-1.8.0-openjdk, java-11-openjdk, java-17-openjdk, java-latest-openjdk, recutils, suricata, and zchunk), Oracle (firefox and kernel), Red Hat (firefox), Scientific Linux (firefox), Slackware (mozilla, openssl, and seamonkey), SUSE (apache2-mod_auth_mellon, libvirt, and pgadmin4), and Ubuntu (dpdk, mysql-5.7, networkd-dispatcher, openssl, openssl1.0, sqlite3, and twisted).

[$] LWN.net Weekly Edition for May 5, 2022

Čet, 05/05/2022 - 04:05
The LWN.net Weekly Edition for May 5, 2022 is available.

[$] Modern Python performance considerations

Sre, 05/04/2022 - 23:34
There is a lot of work going on right now on speeding up Python; Kevin Modzelewski gave a presentation at PyCon 2022 on some of that work. Much of it has implications for Python programmers in terms of how to best take advantage of these optimizations in their code. He gave an overview of some of the projects, the kinds of optimizations being worked on, and provided some benchmarks to give a general idea of how much faster various Python implementations are getting—and which operations are most affected.