LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090714.mp3

Apologies folks, we’re playing post-Linux Symposium catchup at the moment.

For Tuesday, July 14th 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Hotplug, memory leaks, MPU, OOM and VGA.

Hotplug. Lai Jiangshan noticed that the CPU hotplug code temporarily changes the affinity of running tasks during hotplug operations. This breaks several user-visible behavioral expectations, especially if an error occurs during the hotplug operation, in which case the affinity may not be restored to the previous assigned configuration. The patch aims to rectify this behavior.

Memory leaks. Alexey Fisher, Pekka Enberg, and Catalin Marinas had a debate about the possible existence of as many as 60 memory leaks on Alexey’s system, especially affecting ext4. Catalin’s kmemleak checker was reporting that the system in question was leaking memory and ultimately decided that the leak warnings were legimate and not further unwanted noise from kmemleak itself. Catalin posted a new thread specifically on ext4 and requested that the ext4 developers provide clarification of their intended behavior in the code.

MPU (Memory Protection Units). Mike Frysinger posted a patch and accompanying explanation of the advanced features of modern MMU-less architectures. Even though these systems lack a full blown Memory Management Unit (MMU) and virtual memory (usually for reasons of cost and complexity), certain architectures – like the Blackfin – actually provide some protection against memory corruption even without virtual memory. The MPU allows protections against specific ranges of physical memory by programming processor registers, similar to e.g. BATs on other architectures.

OOM. Gene Haskett and Fengguang Wu continued debating the recent spate of OOM killer attacks in 2.6.31 rc kernels. Gene noted that his test box has been “boringly stable” with recent kernels and so he was going to reboot it as the “witching hour” was rapidly approaching with regard to finding OOM problems. Separately, Rik van Riel posted a patch that preserves a task’s oom_adj value on fork (clone), which seems like a very good idea to this author.

VGA. Tiago Vignatti posted a generic VGA arbiter implementation. This is necessary for legacy graphics cards providing mapping of legacy VGA IO addresses such that two cards both supporting legacy VGA do not fight for the addresseses in question. The patch includes documentation.

In today’s miscellaneous items: A fix to the readdir() implementation for procfs such that TGIDs not previously showing up in the directory listing would be shown (Nikanth Karthikesan), an implementation of gmtime and localtime for the kernel (based on glibc) from Zhao Lei (however this author wonders whether there isn’t already an implementation of this – it seems dubious there would not already be something available in the kernel time code), various core, x86, tracing, and timer fixes from Thomas Gleixner, infiniband fixes from Roland Drier, dlm fixes from David Teigland, some fairly serious networking fixes from David Miller (including a fix for missing methods in the netdev_ops network device driver conversion process by Stephen Hemminger et al), libata updates (Jeff Garzik), and some compilation warning fixes.

In today’s announcements: Pierre Ossman posted requesting a new maintainer for the MMC subsystem since he doesn’t have enough time these days to give it the love that he would like to give.

The latest kernel release was 2.6.31-rc3, which was release by Linus on the weekend.

Stephen Rothwell posted a linux-next tree for July 14th. Since Monday, Stephen dropped the USB (quilt import problem) and Staging (depends on USB) trees and the overall linux-next tree still fails to build in an allyesconfig build configuration on powerpc. Several other failures necessitated patches. The total sub-tree count in the day’s compose is steady at 132 trees.

That’s a summary of today’s LKML traffic. For further information visit kernel.org. I’m Jon Masters.