LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090623.mp3

Do you pine for the days when men were men and wrote their own device drivers? Well, do you, punk?

For Tuesday, June 23rd 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: the continuing 2.6.31 merge window, IDE, Intel Trusted Execution Technology support, RCU, SFI, System Call tracepoints, and removing perl from the kernel build process.

The Continuing 2.6.31 merge window

per-bdi writeback threads. Jens Axboe wondered what was going to be done about his per-bdi writeback patch series, which are apparently “looking good” and have been in linux-next for almost a week without any problem reports. Jens wasn’t the only person wondering where his patches went. K. Prasad mailed to ask what was the plan with regard to his Hardware Breakpoint Interfaces, especially considering that (apparently), most of the previous concerns from Ingo Molnar and others have now been addressed in -tip.

Architecture updates include: Super-H from Paul Mundt (mostly SMP fixups), blackfin (Mike Frysinger, including a fair number of fixes from himself), and the new S+core architecture that was mentioned in this podcast previously. This ARM-reminiscent architecture is living in Arnd Bergmann’s tree at the moment while it’s author (Liqin Chen, who seems to be doing a great job figuring out Linux kernel development, including being the first user of Arnd’s new asm-generic defined ABI) figures out where to keep the 200kb tree. Currently, S+core runs LTP and a limited userland, but not against this tree.

Miscellaneous updates include: backlight updates (Richard Purdie, including a trivial kmalloc fix), LED driver support (also Richard Purdie, essentially bug fixes but also one new driver), infiniband (Roland Dreier), SCSI updates (James Bottomley, mostly a small set of driver updates and fixes), asm-generic fixes (Arnd Bergmann, whose tree is also hosting a new architecture port), fixes to watchdog (Wim Van Sebroeck), libata updates (Jeff Garzik), run-time power management of IO devices (Rafael J. Wysocki), and Kprobes jump optimization (replacing int3 breakpoints on x86 with jumps). For those interested in a discussion of git usage in kernel development, take a look at Linus’ replies to the “fix for shared flat binary format in 2.6.30″ thread.

Non-merge specific concerns

IDE. Following yesterday’s rather abrupt announcement that David Miller would be taking over IDE maintainership, Tuesday brought a number of clarifications. First, Bart and David showed public support for one-another, with Bart saying he would have more time for “other projects”, and David explaining that this was all amicably done (so nobody need worry about the event – the sky is not falling and we can move on with our lives). Secondly, David posted a new patchwork location for those wishing to track ide patches in the future.

Intel Trusted Execution Technology support. Joseph Cihula posted version 5 of a patchset implementing Trusted Execution Technology support for Linux. As I have previously discussed, this patch series is intended to safeguard against a compromised system via ensuring all of the elements in the boot path are secure from attack. The technology aims to verify that the bootloader is secure, which then verifies the kernel, and so forth. It is implemented in the form of a tboot “kernel” loaded by the bootloader that sets up the dynamic root of trust via a special GETSEC[SENTER] processor instruction and then causes the real kernel to be loaded, after it has been verified.

RCU. Paul McKenny posted a -tip proof of concept version of RCU designed for non-SMP, embedded systems, aiming to be small in footprint (as little as a quarter the size in memory use terms as other RCU options, according to the benchmarks that he attached to the posting). In addition to Paul’s patches, Jesper Dangaard Brouer posted a 10 part patch series aiming to ensure correct usage of rcu_barrier on module unload. Let’s remind ourselves that this issue was “discovered” last week and so far has resulted in a few fixes to David Miller’s net tree, with more to follow, including these patches.

SFI. Len Brown posted a patch series implementing a new “Simple Firmware Interface” (for which a talk is forthcoming at next month’s Linux Symposium), which seems to be a simplified version of ACPI curretly with a single chipset implementation. While the idea is certainly interesting, Matthew Garrett was concerned that having essentially another ACPI (sub)implementation in the kernel was setting a precident for more to follow. He prefered codebase sharing as the starting point, allowing for other sub-ACPI variants.

System call tracepoints. Jason Baron posted version 2 of his patch series implementing system call tracepoints. It includes the ability to toggle entry/exit tracing of each system call via the usual events/syscalls/syscall_blah/enable type interface. Since the previous version, Jason has added a number of fixes (locking, static allocation, etc), including support for system calls that take no argument.

Finally today, Rob Landley posted a three part patch series removing the use of perl from the 2.6.30 build, and replacing the offending perl script (kernel/timeconst.pl) with a much shorter (a quarter of the size) shell script that does the same thing. Separately, Benjamin Herrenschmidt continued the good fight figuring out how to make early SLAB initialization work on PowerPC. Amongst his findings was a need to move cpu_hotplug_init early enough, to which Linus responded that this could just be a statically initialized.

In today’s announcements: RT version 2.6.29.5-rt22. Thomas Gleixner announced version 2.6.29.5-rt22 of the -rt patchset. The announcement contains three kinds of fixes – a network live lock fix, disabling preemption over the atomic section of iomap, and identifying false positivies in softirq pending check (caused by a CPU going idle with the softirq pending bit of a blocked softirq thread still set).

The latest kernel release is 2.6.30, which was released by Linus on June 9th.

Stephen Rothwell posted a linux-next tree for June 23rd. Since Monday, he added a fix for an fbdev exposed compiler bug, the slab tree lost its build conflict, and yes, the powerpc tree continues to fail in an allyesconfig build configuration. The total sub-tree count remains steady at 130 trees.

That’s a summary of today’s Linux Kernel Mailing List traffic, for further information visit www.kernel.org. I’m Jon Masters.