August 2013 Linux Kernel News

Linus Torvalds released 3.11. Prior to 3.11 release, Linus's 3.11-rc7 announcement was posted to his Google Plus page on Linux's 22nd birthday. Here is what he had to say in his nostalgic and reminiscent statement of the passing of time in which so much has been accomplished.

"Hello everybody out there using Linux -

I'm doing a (free) operating system (just a hobby, even if it's big and
professional) for 486+ AT clones and just about anything else out there
under the sun. This has been brewing since April 1991, and is still not
ready. I'd like any feedback on things people like/dislike in
Linux 3.11-rc7.

I originally ported bash(1.08) and gcc(1.40), but others have taken over
user space and things still seem to work. This implies that I'll get the
final 3.11 release within a week, and I'd like to know what features most
people would want. Any suggestions are welcome, but I won't promise I'll
implement them :-)"

Mainline Release (Linus's tree) News

3.11 is now released and 3.12 merge window is open. Several bug fixes have been included in the final 3.11 release. There are 80+ commits since 3.11-rc7 and here is short summary of a few critical fixes.

x86/mm: Fix boot crash with DEBUG_PAGE_ALLOC=y and more than 512G RAM

This fixes a bug that was introduced when was changed to to use #PF handler to to set memory mappings.

drm/i915: ivb: fix edp voltage swing reg val

This fixes eDP link-training failures bug introduced in drm/i915 enhancements for Ivybridge eDP that causes a blank screen.

drm/vmwgfx: Split GMR2_REMAP commands if they are to large

Fixes a bug that causes VM to die when a large SVGA command is issued. This change splits the command to avoid issuing large SVGA commands.

3.12 git pull request summary

One important feature that might be included in the 3.12-rc1 is the patch series that adds a CPU idle driver for the vexpress TC2 testchip. This work is an evolutionary step towards an ARM unified CPU idle driver based on the Multi-cluster power management (MCPM) framework.

This patch set adds:

  • GIC driver update to add a method to disable the GIC CPU IF
  • - TC2 MCPM update to add GIC CPU disabling to suspend method
  • - TC2 CPU idle big.LITTLE driver

The MCPM framework is designed to handle power management in big.LITTLE architectures that consist of clusters that at the two ends of power spectrum. Slow highly power-efficient ARM cups in some clusters and fast power-hogs in others. This makes for a challenging scenarios for making decisions on powering up and shutting down clusters. The MCPM framework defines state machine that would help kernel transition clusters through various power states such as down, up, and the transition state of going down. More on this can be found in Jonathan Corbet's Multi-cluster power management article.

ACPI and power management updates for v3.12-rc1

Linux ACPI PM maintainer Rafael Wysocki says "the headline feature of this pull request, is the addition of Intel Thunderbolt support on systems that use ACPI for signaling Thunderbolt hotplug events". Please note that this doesn't include Apple.

The change of cpufreq ondemand governor that makes it choose target frequencies proportional to load is another important change that is included in this git pull. It simplifies the code and might improve performance and reduce energy consumption slightly on systems using this governor. This change has been in linux-next since 3.11-rc1 and there have been no issues reported.

In addition to that, the old and long deprecated /proc/acpi/event interface is going away.

Another notable 3.12 enhancement is the Platform Framebuffers and SimpleDRM feature by David Herrmann. This feature simplifies the firmware framebuffers handling on x86 architecture by introducing the simple-framebuffer platform device where-ever it is applicable and also adds SimpleDRM driver which is a simplefb driver. Please refer to for more information on this feature.

Stable release News

As of this writing:
Current latest stable release is 3.10.10.
Longterm stable releases are 3.0.94, 3.2.50, and 3.4.60.
Extended stable releases are and
Longterm releases for 2.6.y are and

Linux RT stable releases are 3.0.89-rt117, 3.2.50-rt70, 3.4.57-rt72,, and 3.10.10-rt7

Upcoming LinuxCon North America and co-located events

LinuxCon North America is scheduled to be held from September 16-18, 2013 in New Orleans, LA. Linux Conferences provide opportunities to developers to come together and discuss new ideas, solutions to problems in face to face meetings. In addition to face to face developer meetings, Linux Conferences also include presentation on various Linux Kernel and Linux Kernel eco-system topics.

Several other events and summits are co-located with the LinuxCon NA. Linux Plumbers Conference, Xen Project User Summit, Linux Wireless Summit, and Linux Security Summit to mention a few. For a complete list of co located events and please check:…

The LinuxCon schedule can be found at:…

The Linux Plumbers Conference schedule is at:

LPC - ACPI/PM, PCI subsystems I Microconference

Several topics are on the agenda for discussion at this micro-conference:

ACPI vs Device Tree - Discussion on the two device enumeration methods and how to support new ARM systems that support both.

SR-IOV Virtual Function Lifetimes - Discussion of issues around enabling, disabling, and removing Virtual Functions

PCIe Native Hotplug Integration with ACPI-Based Hotplug - Discussion on how to integrate the native PCIe hotplug (pciehp) with ACPI-based PCI hotplug (acpiphp).

mm: Memory Power Management

Memory power management is an area that is seen as the next big target for power management as the system RAM keeps on getting larger and larger.

Srivatsa S. Bhat has been enhancing Linux MM to be aware of memory regions that have power management capabilities and hence can be included in the power management policies.

Final Thoughts

Next up is the 3.12 merge window and then the 3.12-rc1 release. Based on the git pull requests for 3.12 it will include simplefb on x86, and the initial work to unify ARM CPU idle driver. In addition to that, based on the work that is progress, 3.12 might include power-ware Linux MM and a more complete ARM unified CPU idle driver based on the Multi-cluster power management (MCPM) framework, and a completed simplefb and SimpleDRM feature for x86.

Linux since its birth on August 25th 1991, went from its humble beginnings of running just the 486+ AT clones, now runs the world. Remember the phrase "Resistance is futile!" and what a total domination it is in winning hearts and minds one at a time.

Thinking about it in a different way, the world is thankful for Linux and the open source rescuing us all from Closed and Proprietary world. I wonder how many people could have foreseen the turn of events when the first announcement came out and how many people can imagine going about their normal busy lives without using a device running Linux knowingly and unknowingly.

The beauty of it is, Linux's unending pursuit of perfection one patch at a time and one release at a time. It is possible because of the commitment of thousands of individuals that love and enjoy every little bit they can do to evolve Linux one step closer to perfection with a moving target end goal. "Live long Linux and flourish."

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