See also: last week's Kernel page.

Kernel development

We mentioned last week the new sequence of "pre" pre-patches. The first 2.3.99pre-4 prepatch contains a number of architecture-specific updates, a new CPiA video camera driver (which relocates and adds to the existing USB support for this device), many changes to the eepro100 ethernet driver, a number of USB serial changes, a StrongARM 1100 LCD frame buffer driver, NFS updates, and some networking fixes.

Alan posted an updated version of his 2.3.x job list.

The current stable kernel release is still 2.2.14. The latest prepatch, 2.2.15pre16, includes two security fixes, for the exec and ELF loader problems and for the "ftp back masquerade" vulnerability. Another prepatch will be released if a fix for a recently announced UDP masquerading bug comes out quickly enough.

POSIX threads. The issue of support in the Linux kernel for POSIX threads came up again this week. Many people who are looking for a clean, cross-platform implementation of threads get frustrated that they are not fully supported by the Linux kernel. The final answer is that they won't be implemented. The concensus among the primary kernel developers appears to be that doing a POSIX threads implementation is impossible to do both correctly and efficiently. Here's a sample of some of the opinions:

Alan Cox:

"posix threads is a braindamaged pile of crap".

Stephen Tweedie:

"although a lot of the POSIX threads are reasonable, things like requiring uid/gid updates to be instantly effective across all threads in the process are just insane".

Linus Torvalds:

"Note that the reason the kernel is not POSIX-compliant is:
- the POSIX standard is technically stupid. It's much better to use a cleaner fundamental threading model and build on top of that.
- things like the above are just so much better and more easily done in user space anyway."

Local Denial of Service against the Linux kernel. Jay Fenlason posted a note to Bugtraq covering a local denial-of-service attack that impacted both the 2.2.14 and the 2.3.99-pre2 kernels. Alexey Kuznetsov responded with a patch for 2.3for the problem.

Support for large disks (>32GB). A discussion was initiated by David Elliott this week on how to support disks larger than 32GB on systems with older BIOS. It provided an interesting example of the complexity introduced into an operating system in order to handle essentially broken hardware. H. Peter Anvin commented, "Remember... most hardware/firmware is broken. Part of what makes a good OS is to work with broken hardware without sacrificing working with properly working hardware." In the end, Andre Hedrick outlined his preferred solutions for the problem, to which most people seemed to agree.

kswapd fix. Russell King reported a problem with kswapd where it looped unnecessarily, chewing up unneeded CPU cycles. Rik Van Riel took Russell's first effort at a patch and cleaned it up for inclusion in an upcoming 2.3.x prepatch.

Timpanogas NetWare filesystem releases. The Timpanogas Research Group has announced the release of its NWFS 2.2 NetWare file system. NWFS is released under the GPL. They have also announced the forthcoming release of the M2CS clustered storage system and M2FS distributed filesystem.

The endless overcommit thread .... The endless linux-kernel thread discussing overcommit lived up to its name this week. We won't touch upon the issues again, continuing to redirect you to the March 9 discussion of this, since nothing new and wonderful has been added to the discussion since. However, we couldn't resist a pointer to this note from Richard Johnson on the topic, if only for the amusement value.

Other patches and updates released this week include:

• packet-0.0.1l, update to the packet writing module for ATAPI and SCSI CD-RW units from Jens Axboe.

• fault statistics addition to /proc/stat by Pat O'Rourke.

• interrupt latency measurement tool from Andrew Morton.

• resource priority daemon from David Whysong.

• fairsched-0.30, a hierarchical fair CPU scheduler from Borislav Deianov.

• simple fair scheduler patch from Rik van Riel.

Section Editor: Jonathan Corbet

For other kernel news, see: Kernel traffic Kernel Newsflash Kernel Trap Linux 2.5.x Porting help

Other resources: Kernel Source Reference L-K mailing list FAQ Linux-MM Linux Scalability Effort Kernel Newbies Linux Device Drivers

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