LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090622.mp3

Would you be prepared if gravity reversed itself? The only thing I can’t figure out is how to keep the change in my pockets.

For Monday, June 22nd 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: the continuing 2.6.31 merge window, the IDE tree, documenting the rc-series and the merge window, taking a core dump, kernel boot delay madness, IO scheduler based IO controllers, and some feedback.

The Continuing 2.6.31 merge window

Device Mapper. Alasdair Kergon posted a series of device mapper patches. These are mostly a consolidation of various fixes, including ioctl support cookies for udev, and some documentation updates.

Firewire. Stefan Richter posted a series of firewire (IEEE1394) update. In this posting, Stefan notes that the “new” stack is now preferable over the legacy one, except in the case of audio devices (for which he notes that it is possible for distributions to package both stacks in their releases).

Networking. David Miller posted a series of updates to the networking stack (including an indirect reminder that John Linville is away at the Wireless summit at the LinuxTAG in Berlin this week). Amongst the updates were lots of fixes, and he still expects some netfilter regression fixes to follow. Separately, David wondered aloud how the NMI watchdog and NOHZ might interact badly if a system were truly idle (triggering the NMI watchdog unncessarily), but ultimately convinced himself that he was looking for another SPARC cause.

NFS private namespaces. Tond Myklebust reposted his private namespaces for NFS series of patches. When these are applied, the kernel gains the ability to create a private mount namespace that is not visible to user processes. These were originally targeted for 2.6.31 and in the absence of objections, Trond is hopeful that they will be ACKed and accepted forthwith.

PCI. Jesse Barnes posted an updated PCI git repository. He points out that the latest updates are “much less aggressive” than those targeting 2.6.30, although he noted that the latest tree does include AER (Advanced Error Reporting) enhancements, especially on multiple error conditions.

Performance counters. Ingo Molnar responded with a series of replies to a long series of replies from Stephane Eranian concerning Ingo’s posting of Performance counters patches for the merge window. There were many different comments here, but they showed a difference in opinion between the various potential users for performance counters. Ingo states that his main concern is making tools (such as perf) a “useful solution to developers/users”, which is “a key area where…perfcounters and perfmon differs”. He also notes that it aims to be “‘Oprofile done right’ and’pfmon done right’”. The thread makes for some interesting reading if you are interested in performance counters (and, honestly, who listening to a podcast such as this one wouldn’t be?).

Architecture updates include: s390 (Martin Schwidefsky).

Miscellaneous updates include: irqfd/eventfd patches from Gregory Haskins, suppressing page allocator warnings about order >= MAX_ORDER when the code causing this is doing the right thing and intentionally gets the warning (by adding a new __GFP_NOWARN kmalloc flag), exofs/osd tree updates from Boaz Harrosh, and a rather interesting one from Krzysztof Mazur noting that arch_get_unmmaped_area() in the generic core doesn’t correctly ensure that the address it returns is greated than TASK_UNMAPPED_BASE.

Non-merge specific concerns

The IDE tree. David Miller and Bartlomiej Zolnierkiewicz had a “discussion” in which David expressed some frustration about the lack of testing of various bug fixes, to which Bartlomiej suggested that David might take over IDE, which David offered to do on the spot. He posted a new IDE tree address, and various folks sent well wishing mails. But Linus wasn’t so keen on the situation, saying that he really didn’t want to take the tree David Miller had put together. Quoting Linus, “I really don’t want to take this. I think you [David] and Bartlomiej should spend a _lot_ more time and effort trying to resolve this. Me taking it just closes the doors fro trying to be constructive about issues.” There followed a debate about the current users of ide vs. pata. and libata, and why more people don’t just move away from legacy ide code. Arnd Bergmann pointed out that a number of architectures (especially those without dma-mapping.h support, often true for the NOMMU architectures) can’t use libata at all.

Documenting the rc-series and merge window. Luis R. Rodriguez reposted his quite excellent documentation on the rc-series and merge window process. In the latest version, he adds the average time between the last ten releases (86.0 days currently).

Taking a core dump. Neil Horman posted an interesting little patch that aims to fix three deficiencies in the current core dumping code. Firstly, he fixes recursive dump handling (where the dump handler specified in core_pattern actually crashes while it is helping us to take the full dump). Secondly, Neil allows the core_pattern process to complete, waiting for it in case it wants to poke at the procfs entries for the crashee process. Finally, he adds a brand new sysctl called core_pipe_limit that bounds parallel core dumps.

Kernel boot delay madness. David Miller objected to a patch from Simon Arlot adding yet another boot parameter to the kernel, this time to obviate a (possible 2 seconds in duration) reset delay for physical network PHYs that have already been initialized on boot. David objected that “this is getting out of control” (refering to the boot delay parameter craziness), adding “We’re not going to add a hundred different obscure module options to eliminate delays and device resets”.

IO scheduler based IO controllers. Vivek Goyal followed up to his Friday posting concerning the latest iteration of his IO scheduler IO controller, noting that he had not done testing with AIO (Asynchronous Input Output). A dialog ensued between Vivek and Jeff Moyer over the best options to use for benchmarking to ensure that DIRECT IO was also being requested.

Finally today, thanks for the feedback on this podcast. It really means a lot to me that I’m providing something of some value to the community, and having a little fun in the process, especially at 4am on a Sunday morning. Do drop me a line and let me know what you think! If you’d be willing to record a few words about what you work on for me during the OLS or Plumbers conference, please do let me know, or just find me at the event and we’ll hook it up.

In today’s announcements: git version 1.6.3.3. Junio C Hamano announced git version 1.6.3.3, which includes fixes for cygwin, memory leaks, and a number of others fixes.

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 22nd. Since the previous day, two new trees were added for davinci and my hwlat hardware latency detector. Stephen also pulled in the “new” ide tree, although that might change if the discussion is revived following Linus’ comments. Today’s tree is moslty tree of conflicts, and yes, powerpc still fails to build in an allyesconfig build configuration. The total sub-tree count is now up to 130 trees, due the addition of the two aforementioned new sub-trees.

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