Hírolvasó

The kernel's thread model is relatively straightforward and performs reasonably well, but that's not enough for all users. Specifically, there are use cases out there that benefit from a lightweight threading model that gives user space control over scheduling decisions. Back in May 2021, Peter Oskolkov posted a patch set implementing an abstraction known as user-managed concurrency groups, or UMCG. Several revisions later, many observers still lack a clear idea of what this patch is supposed to do, much less whether it is a good idea for the kernel. Things have taken a turn, though, with Peter Zijlstra's reimplementation of UMCG.

Security updates have been issued by Debian (djvulibre, libzip, monit, novnc, okular, paramiko, postgis, rdflib, ruby2.3, and zziplib), openSUSE (chromium, kafka, and permissions), and SUSE (net-snmp and permissions).

The 5.16-rc7 kernel prepatch is out for testing. "Obviously the holidays are a big reason it's all small, so it's not like this is a sign of us having found all bugs, and we'll keep at this for at least two more weeks".

Security updates have been issued by Debian (apache-log4j2, libextractor, libpcap, and wireshark), Fedora (grub2, kernel, libopenmpt, log4j, mingw-binutils, mingw-python-lxml, and seamonkey), Mageia (golang, lapack/openblas, and samba), and openSUSE (go1.16, libaom, log4j12, logback, and runc).

It is past time for another release of Is Parallel Programming Hard, And, If So, What Can You Do About It?. But first, what is the difference between an edition and a release?

The main difference is the level of validation. For example, during the several months leading up to the second edition, I read the entire book, fixing issues as I found them. So where an edition is a completed work, a release is primarily for the benefit of people who would like to see a recent snapshot of this book, but without having to install and run LaTeX and its dependencies.

Having cleared that up, here are the big-animal changes since the second edition:

1. A lot of detailed work to make the new ebook-sized PDF usable, along with other formatting improvements, courtesy of Akira Yokosawa, SeongJae Park, and Balbir Singh.
   
2. The nq build now places quick quizzes at the end of each chapter, courtesy of Akira Yokosawa.
   
3. There are a few new sections in the “Locking” chapter, the “Putting It All Together” chapter, the “Advanced Synchronization: Memory Ordering” chapter, and the “Important Questions” appendix.
   
4. There is now more validation information associated with much of the sample code throughout the book.
   
5. The “RCU Usage” section has received a much-needed upgrade.
   
6. There is now an index and a list of acronyms, courtesy of Akira Yokosawa.
   
7. A new install_latex_package.sh script, courtesy of SeongJae Park.
   
8. Greatly improved error handling, including scripts that check for common LaTeX formatting mistakes, courtesy of Akira Yokosawa.
   

Yang Lu and Zhouyi Zhou are translating the Second Edition to Chinese, and would greatly appreciate additional help.

Everyone mentioned above contributed a great many wordsmithing fixes, as did Chin En Lin, Elad Lahav, Zhouyi Zhou, and GitHub user “rootbeer”. A grateful “thank you” to everyone who contributed!

The Jami communication tool has released a major new stable version called "Taranis"; the blog post announcement explains: "Taranis, the Gallic and Celtic god of the sky, lightning and thunder, will be the baptismal name of this new version of Jami." The mailing-list announcement describes the tool this way: Jami is a GNU package for universal communication that respects the freedom and privacy of its users. Jami is an end-to-end encrypted secure and distributed voice, video, and chat communication platform that requires no central server, and leaves the power of privacy and freedom in the hands of users.

Another recent blog post gives an overview of Jami for video conferences. The new release has improvements throughout the system, including the first phase of Swarm support, which are "fully distributed, peer-to-peer chats with conversation histories synchronized across your devices, and the potential to be expanded into group chats in upcoming future releases of Jami".

Security updates have been issued by Debian (webkit2gtk and wpewebkit), Fedora (httpd and singularity), Mageia (ldns, netcdf, php, ruby, thrift/golang-github-apache-thrift, thunderbird, and webkit2), openSUSE (go1.16, go1.17, libaom, and p11-kit), and SUSE (go1.16, go1.17, htmldoc, libaom, libvpx, logstash, openssh-openssl1, python3, and runc).

Version 3.8.0 of the Darktable photo-processing application has been released. Significant changes include a new keyboard shortcut system, a new diffuse-or-sharpen module, a new "scene-referred" blurs module "to synthesize motion and lens blurs in a parametric and physically accurate way", support for the Canon CR3 raw format, and more.

Systemd 250 has been released. To say that the list of new features is long would be a severe understatement; the developers have clearly been busy.

systemd-homed now makes use of UID mapped mounts for the home areas. If the kernel and used file system support it, files are now internally owned by the "nobody" user (i.e. the user typically used for indicating "this ownership is not mapped"), and dynamically mapped to the UID used locally on the system via the UID mapping mount logic of recent kernels. This makes migrating home areas between different systems cheaper because recursively chown()ing file system trees is no longer necessary.

(See this article for a description of ID-mapped mounts).

OVH was pestering me about migrating my VPS from its previous range to the new (and more expensive) one. I finally agreed to that. Migrated the VM to the new host, it launches with no networking. Not entirely unexpected, but it gets better.

The root cause is the DHCP server at OVH returning a lease with netmask /32. In that situation, it's not possible to add a default route, because the next hop is outside of the netmask.

Seems like a simple enough problem, so I filed a ticket in OVH support, basically saying "your DHCP server supplies incorrect netmask, please fix it." Their ultimate answer was, and I quote:

Please note that the VPS IP and our failover IPs are a static IPs, configuring the DHCP server may cause a network issues.

I suppose I knew what I was buying when I saw the price for these OVH VMs. It was too cheap to be true. Still, disappointing.

Version 5.0 of the Krita painting program has been released. "This is a huge release, with a lot of new features and improvements". Changes include a reworked resource system, dithered gradients, faster color management, a reworked animation subsystem, and more; see the release notes for details.

Security updates have been issued by Debian (openjdk-11), Fedora (keepalived and tang), openSUSE (openssh, p11-kit, runc, and thunderbird), Oracle (postgresql:12, postgresql:13, and virt:ol and virt-devel:ol), Red Hat (rh-maven36-log4j12), and SUSE (ansible, chrony, logstash, elasticsearch, kafka, zookeeper, openstack-monasca-agent, openstack-monasca-persister-java, openstack-monasca-thresh, openssh, p11-kit, python-Babel, and thunderbird).

The LWN.net Weekly Edition for December 23, 2021 is available.

It may have seemed questionable at times, but we have indeed survived yet another year — LWN's 22nd year of publication. That can only mean one thing: it is time to take a look back at our ill-advised attempt to make predictions in January and see how it all worked out. Shockingly, some of those predictions were at least partially on the mark. Others were ... not quite so good.

Back at the beginning of 2020, it was predicted that retirements would increase during this decade. In 2021, the prediction was that retirements would increase over the next couple of years. It is happening and LWN is no exception. I am retiring at the end of this year after more than 20 years with LWN.

So who am I and how did I get here? To some, I'm a name at the bottom of some LWN page. To a few, I'm the one that reminds them when their LWN group subscription is about to expire. You might have even met me at a conference. Not that I have been to very many. Mostly I tend to be quietly in the background watching the LWN mailbox, looking for brief items and quotes of the week (sorry I haven't found much lately), proofreading articles, managing subscriptions, and more. But I'm older than most of you and this is my last LWN weekly edition. Getting here is a bit of story.

Today's stable kernel updates are 5.15.11, 5.10.88, 5.4.168, 4.19.222, 4.14.259, 4.9.294, and 4.4.296. Each contains another set of important fixes.

Security updates have been issued by CentOS (firefox, ipa, log4j, and samba), Debian (sogo, spip, and xorg-server), Fedora (jansi and log4j), Mageia (apache, apache-mod_security, kernel, kernel-linus, and x11-server), openSUSE (log4j and xorg-x11-server), Oracle (kernel, log4j, and openssl), and SUSE (libqt4 and xorg-x11-server).

Fedora is among the group of Linux distributions that, by default, lock out the root account such that it does not have a password and cannot be logged into. But, traditionally, "rescue mode" boots the system into single-user mode, which requires a root password—difficult to provide if it does not exist. A Fedora proposal to remove the need for the password in that case, and just drop into a root shell, does not seem likely to go far in that form, but it would seem to have pointed toward some better solutions for the underlying problem.

The Linux Foundation has announced the posting of a report on its research into diversity, equity, and inclusion in open-source communities.

The research shows that while a majority of respondents feel welcome in open source, many in underrepresented communities do not. We hope that the data and insights that this project provides will be a catalyst for strengthening existing DEI initiatives and creating new ones.

The full report can be downloaded from this page.

Security updates have been issued by Mageia (log4j), openSUSE (chromium, log4j, netdata, and nextcloud), Oracle (kernel and kernel-container), Red Hat (kernel, kernel-rt, log4j, openssl, postgresql:12, postgresql:13, and virt:rhel and virt-devel:rhel), Slackware (httpd), SUSE (xorg-x11-server), and Ubuntu (firefox).