LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090709.mp3

I’ve been in the air for 32 hours over the past few days, on a 3 day trip to Japan, apologies for lag, jetlag, and catchup I’m now playing.

For Thursday, July 9th 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Kmemleak, Mudflap, and OOM.

Kmemleak. Catalin Marinas posted a number of kmemleak fixes aimed at reducing the false positive leakage warnings down to near-zero (”making it usable”). The latest patches include support for large block allocations in SLUB and correct handling of bootmem allocations. Catalin also noted a potential leak in alloc_pid, as evidenced in a lost pid structure for an Xorg server started by gdm on Catalin’s system, and reported in a separate thread.

Mudflap. Janboe Ye posted an RFC patch implementing GCC mudflap support for the Linux kernel. GCC Mudflap is a feature of the compiler that will cause an application (linked against libmudflap) to check all “risky” pointer allocations, and aims to reduce all kinds of memory abuses. Although tools such as Kmemleak can already find many cases of memory leakage, kmemleak can’t do this after the SLAB in question has been freed. Janboe’s patch looks interesting, although I haven’t time to dig any further yet.

OOM. Rik van Riel posted a patch aimed at addressing some of the recent OOM situations, as touched upon in yesterday’s podcast. Rik noticed that vmscan can get horribly confused when too many tasks go into direct reclaim, and trigger an OOM situation that is caused because too few pages are on the LRU. Instead, Rik proposes limiting the number of tasks that may enter page reclaim to allow at most half of each inactive list to be isolated at any one time. In yet another semi-related VM thread, Kosaki Motohiro posted version 2 of his patches aimed at helping to track down OOM situations with more information presented to the user in the generated kernel log messages.

In today’s miscellaneous items: Version 3 of the Zero Page re-introduction patches (Kamezawa Hiroyuki) that were so well covered by Linux Weekly News recently, version 7 of the memory barriers for poll and receive network callbacks (Jiri Olsa – recall the original product bug report which lead to finding this generic problem back for version 1 of the patch), a fix for network device carrier detection for devices utilizing phylib (Anton Vorontsov), continued discussion of what makes a “good” tty driver, removal of the old (and quite deprecated) pre-x86 merge x86 MCE code (Andi Kleen), an added export of atomic64 symbols for non-64 arches (Roland Dreier), some networking updates (David Miller – including the memory barrier fixes from Jiri Olsa, and a number of other bug fixes), some ongoing discussion of the “tmem” patches in which arguments were put forward for alternative ways to provide a voltile cache to processes (especially virtual machines) without lots of extraneous copying, and version 11 of the kprobe based event tracer utilizing the ftrace tracing interface (Masami Hiramatsu). On another tracing related note, Robet Richter posted some OProfile cleanups.

In today’s announcements: linux-rt version 2.6.29.6-rt23. Thomas Gleixner announced version 2.6.29.6-rt23 of the linux-rt patchset. It contains some compiler fixes, a powerpc highmem fix, a smp_processor_id fix to hwlat, and some ktime_get speedups. It is also rebased upon 2.6.29.6.

The latest kernel release is 2.6.31-rc2, which was released by Linus on the 4th of July (except it isn’t – there’s a newer version since this time).

Stephen Rothwell posted a linux-next tree for July 9th. Since Wednesday, a new tree entitled “thumb-2″ has been added (presumably ARM related), the tree still fails to build in an allyesconfig build configuration on powerpc, a number of new conflicts appeared, and some build failures also. There are now a total of 132 sub-trees in today’s linux-next composition once more.

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

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090708.mp3

I’ve been in the air for 32 hours over the past few days, on a 3 day trip to Japan, apologies for lag, jetlag, and catchup I’m now playing.

For Wednesday, July 8th 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Modules, OOM, Lockless Ring Buffer, and VFAT.

Modules. In the second module-related item of the week, Siarhei Liakh posted a patch adding support for RODATA protection (via the RO/NX page protection bits) to kernel modules. This affords LKMs (Loadable/Linux Kernel Modules) the same protections as regular kernel code, using available hardware protection mechanisms for enforcement. Arjan van de Ven expressed his approval.

OOM. Another recent OOM cause was isolated in vmscan for systems without swap (or otherwise with more anon pages than file pages). Wu Fengguang says that he has tested the latest “vmscan don’t isolate too many pages” patch and that it solves his OOM, but now the process entering reclaim could sleep long enough to trigger a soft-lockup watchdog instead.

Lockless Ring Buffer. Steven Rostedt posted to let us know about his lockless ringbuffer, which has been discussed before and which is covered in an excellent story this week on Linux Weekly News. Do be sure to take a look at the page swap mechanism for which a patent application has been filed – and be sure to read Steven’s excellent paper/description on the process.

VFAT. Andrew Tridgell posted a summary of the VFAT discussions, and noted a new tree on kernel.org containing his previous proposed ‘workaround’. He isn’t confident that the current patches will make it into the kernel – for many reasons – but is willing to maintain the tree and hopes that he can address some of the technical concerns that have been raised before pushing for inclusion in the kernel once again.

In today’s miscellaneous items: a fix to elfcore.h to enable building UML (Parag Warudkar), some wireless tree updates (John Linville), a patch adding support for the security processor chip and a separate patch adding a driver for the “Restricted Access Region Register” (apparently an ability to restrict access to memory ranges from the CPU) on the Intel MID Platform (Mark Allyn), various cleanups to MAINTAINERS (Joe Perches), some minor powerpc cleanups (Ben Herrenschmidt), some input updates (Dmitry Torokhov), a conversion of ext2 to use the new truncate mechanism (Nick Piggin), a new uevent emmission on block device write protect attribution change, some Power Management updates (Rafael J. Wysocki), and some System 390 updates (Martin Schwidefsky).

Finally today, your author continues to be interested in the memory c-group notification patches, which should make it possible to implement proper memory reservations in the GNU C-library, if it is wired up that way around. I would love to know whether application developers are looking at this – imagine Firefox selectively relinquishing cached web pages from memory on demand.

In today’s announcements: SCST Target driver support for Emulex lpfc FC/FCoE adapters. Vladislav Bolkhovitin posted to announce support for lpfc adapters to be placed in ISCSI initiator and/or target mode using the lpfc SCST driver kit, available on scst.sourceforge.net.

The latest kernel release is 2.6.31-rc2, which was released by Linus over the 4th July weekend.

Stephen Rothwell posted a linux-next tree for July 8th. Since Tuesday, the “sfi” tree was undropped, the tree still fails to build in an allyesconfig build configuration on powerpc, and a number of other conflicts emerged. The total sub-tree count remains steady at 131 sub-trees in the compose.

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