LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20091018.mp3

From London, England, for the weekend of October 18th, 2009, I’m Jon Masters with a summary of the weekend’s LKML traffic.

NOTICE: We got quite behind for a while. Rather than keep being two weeks behind, and now that the merge window is closed for 2.6.32, I am going to jump forward to the present. I will fill in the two week gap through additional back episodes – and if that fails, I’ll do a “summary” show of that period (and mention all the cool things from URCU to the latest Git, stable kernels, 2.6.32-rc3, 2.6.32-rc4, a clone3(!) system call proposal, a trace types registry proposal, and Grant Likely’s awesome work on flattened device trees finally getting properly recognized in the MAINTAINERS file).

Remember, I do this in my spare time and without any help from others. I wanted to make sure the merge window was covered, which is why we lagged, and as Linus says, things have been calm enough over the past two weeks. You could always drop me a line and help me form a group of podcasters. I am interested in hacking up a TurboGears front end to a special LKML site that fellow podcasters could use to easily prep the show – maybe when I’m traveling over the holidays I will spend some time poking at that.

In today’s issue: EDF, ext4, fast symbol resolution, M68K, and the staging tree.

EDF. Raistlin posted the latest RFC version of the EDF (Earliest Deadline First) scheduler patches for wider kernel community consideration, including links to various papers, talks, and news coverage, and also thanking the community for feedback at the recent RTLWS (Real Time Workshop) in Dresden. The patches are available via various git repositories covering users of mainline, sched-devel, and also the preempt-rt patches.

ext4. Parag Warudkar posted a story involving various attempts to use ext3, XFS, and ext4 on his laptop as a root filesystem, and in particular the handling after an unclean forced shutdown due to a failed resume from sleep. His experience anecdotally suggests that ext4 has become more intollerant to unclean shutdowns and so he asks, “is this to be expected or it’s just sheer coincidence?”. Ted T’so followed up, referencing a longstanding bug on kernel.org that he has mentioned before. He says “it’s been frustrating because I have not been ble to replicate it myself; I’ve been very much looking for someone who is (a) willing to work with me on this… and (b) who can reliably reproduce this prolem”. Maybe Parag can help.

Fast symbol resolution. Carmelo Amoroso posted to let everyone know about his “Fast LKM symbol resolution” patches. These add a SysV ELF hash table to speed up module symbol resolution at load time. I was at the Embedded Linux Conference as this year’s keynote speaker. As I expected, Alan Jenkins was also interested in taking a look at this as he has also been looking at ways to speed up symbol resolution through using a binary search. Clearly, as Alan notes, only one of the two solutions is going to work out – so the two of them can now help to figure out which one that is going to be Greg Kroah-Hartman added that he is happy to see the work being done, as obviously most distributions are “forced” to ship very modular kernels.

M68K. Steven King posted a script and a patch that enables merging m68knommu and regular m68k into a single tree, at the inspiration of Sam Ravnborg’s recent efforts to merge the include files. This is a big win because it reduces the amount of code duplication in having two “architecture”s.

Staging. Various discussion has been taking place concerning the impact of effectively removing a driver via the staging tree. This is the case of what to do when an improved or next generational driver is being worked on via the staging tree and will replace a driver that has been removed from mainline. Questions included how should users be made aware of this (given that they are likely using a distribution kernel and thus will only notice many months after the removal occurs), and what onus should be place upon vendors.

In today’s pull requests: some libata fixes from Jeff Garzik, some vbus-enet and vbus fixes from Gregory Haskins (fixing an “illegal” use of a GFP_KERNEL kmalloc within a DEVADD, detected via lockdep and not really seen in the wild), some AMD64 EDAC fixes for 2.6.32-rc6 from Borislab Petkov, some device mapper updates for 2.6.32-rc6 from Alasdair Kergon, some KVM updates against 2.6.32-rc5 from Marcelo Tosatti, some input updates from Dmitry Torokhov, and some inotify/dnotify/fsnotify updates from Eric Paris.

In today’s miscellaneous items: ongoing debate as to the best way to do TSC emulation within Xen (and other virtualized guests in general), a question as to why a software RAID device undergoing reconstruction would cause large numbers of processes to get stuck in a “D” state from Holger Kiehl, a patch adding const qualifiers to various users of quota_format_ops from Alexy Dobriyan, an x86 patch from Andreas Herrmann making use of a new MSR that convieniently includes NodeID and number of nodes per processor meta-data, some thermal patches from Roel Kluin, some Kconfig cleanup patches for powerpc from Kumar Gala, version v0.30 of checkpatch (including a fix for the perl warnings that Andrew Morton had managed to trigger previously), version 3 of some ACPI docking support cleanup patches from Alex Chiang, concerns about a hang on boot when using kgdb from Peter Teoh, a note that the rt2×00 wireless project’s mailing list is actually moderated (although the MAINTAINERS file did not list this fact previously) from Bartlomiej Zolnierkiewicz, a rant about rfkill userspace visible interface changes between 2.6.30.2 and 2.6.31.4 from Olivier Galibert, some miscellaneous MAINTAINERS file cleanups from Joe Perches, and a couple of BKL removal patches from John Kacur (thanks for that, John!).

In today’s announcements: BFS v0.304 stable release. Con Kolivas announced the first officially stable release of his “Brain Fuck Scheduler”. Since the patch is quite large, he posted an URL to download it. Citing the usual warnings about development code, he says it is “known to be quite stable”, though it is apparently relatively easy to trigger a well known keyboard+Xorg failure that has recently been discussed and deemed not to be a BFS issue specifically. He also includes a link to the latest version of the BFS FAQ.

Git version 1.6.5.1. Junio C Humano announced version 1.6.5.1 of the Git SCM (Software Configuration Management) tool as used in development and maintainership of the Linux kernel. The latest release fixes an infinite loop bug when processing corrupted packs, addition of MiB/s download speed listing for fast links, and various other fixes also.

Sparse 0.4.2. Christopher Li announced version 0.4.2 of the sparse kernel source code checker tool as originally written by Linus Torvalds. He is the new maintainer, as previously mentioned on the sparse mailing list, and he thanks Josh Triplett for previously maintaining the project. He also took the opportunity to announce a new kernel.org wiki for the sparse project.

The latest kernel release is 2.6.32-rc5, which was released by Linus on Thursday evening at 18:11:49 Best Coast Time (PDT). As Linus has said several times, this is a “short week” release since he will be at the annual Kernel Summit in Japan and doesn’t want to be doing horribly jetlagged releases. By far most of the changes (90%) since -rc4 are in drivers, and Linus includes a handy git command that you can use to visualize the size of them. Linus hopes that no new regressions were added, noting “like that ever happens”.

Greg Kroah-Hartman announced review patches for the 2.6.31.5 stable kernel.

Stephen Rothwell posted a linux-next tree for September 16th. Since Thursday, there was a new “devicetree” tree (thanks to the awesomeness of that work), the linux-next “fixes” tree still contained a build fix for powerpc/kvm, the kbuild tree still had a build failure that required Stephen to remove include/asm/asm-offsets.h from his object tree, and the tty tree lost its build failure. The total tree count increased to 144 trees.

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

Audio: COMING SOON

For Thursday, October 1st, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: concurrent workqueues, DRBD, VFAT, and writeable overlays.

Concurrent workqueues. Tejun Heo posted an RFC patch series implementing concurrency managed workqueues. The basic premise is that having such an implementation in the kernel keeps the individual workers from having to do it for themselves. The implementation adds a single shared pool of workers per cpu and will attempt to keep the CPU loaded up with as much deadlock-free work as is possible. The code is quite intrusive, illimating RT support from workqueues and touching a lot of code (including the scheduler) but Tejun thinks that, overall complexity will decrease and other code could be removed. David Howells was interested in how this might replace slow-work, and he posted some followup questions for Tejun.

DRBD. “Roland” (devzero) mailed concerning recent comments surrounding DRBD, the distributed replicating block device. He was concerned because a number of people have expressed an interest in these patches not being merged, while DRBD has already been out of tree for around 8 years, and isn’t in staging. He would like to see some more satisfactory resolution for “brilliant things like these” than have them perenially sit out of tree while folks figure out the best way to effect a dm/md merge and a timeframe thereof.

VFAT. Philippe De Muter followed up surrounding his “Simon and Garfunkel” issues (that mp3 files with two tailing dots before the extension were not being properly handled) on VFAT filesystems to say that a recent Windows box wasn’t handling this all too well either. He considers this a bug and isn’t sure that Linux should remain compatible with it, so withdraws his request.

Writeable overlays. Val Aurora posted the latest version of her union mounts and writeable overlays design document, complete with a bunch of patches that she has rebased to kernel 2.6.31, and accompanying tools patches to e2fsprogs and util-linux-ng. Apparently, there will be some review patches soon, though that isn’t an excuse not to start poking. The patches are up at http://valerieaurora.org/union/.

In today’s pull requests: some scheduler fixes from Ingo Molnar (freshly back from a trip, and now believing that it’s “good in all tests”), some networking updates from David Miller, some m68knommu updates from Greg Ungerer, some wireless updates from John Linville, and some btrfs updates from Chris Mason.

In today’s miscellaneous items: a question as to whether IA64 should use a global register for storing per-cpu pointers from Tony Luck, some netfilter patches from Joe Perches, ongoing discussion of alternatives support for cmpxchng64 (silent failure on a cmpxchg of unsupported size annoys Linus, who also provides a commentary on Windows NT’s cmpxcnhg implementation), some autofs4 patches from Ian Kent, version 5 of a fix for too big f_pos handling from Kamezawa Hiroyuki, a suggestion that there might be a buggy implementation in ftrace_profile_enable_event from Paul Mackerras, a series of patches intending to correct usage of __exit_p and __devexit_p from Uwe Kleine-Konig, version 20 of the swap over NFS patches originally worked on by Peter Zijlstra (who is short on time) and now being persued by Suresh Jayaraman, a small update to the optimization flags for the AMD Geode from Matteo Croce, a question about connector and PROC_EVENTS behavior from Kevin Fox, some Kconfig comments cleanups from Michael Roth, and some wonderings from David Miller about the status of mvalloc_user and “perf” mmap patches needed for SPARC to make use of performance events utilities properly.

Finally today, Arjan van de Ven and Andrew Morton continued to discuss the state of the Linux floppy driver, in particular that fact that GCC complains that floppy.c’s ioctl has insufficient bound checks. In response, Andrew stated: ‘gad. You said “floppy” and “ioctl” in the same sentence. Where angels fear to tread.” Separately, Andrew sent an additional error handling patch.

In today’s announcements: The Linux Foundation Technical Advisory Board. James Bottomley posted to let everyone know that there will be elections for the board of the Linux Foundation Technical Advisory Board (TAB) immediately following the forthcoming events in Japan (2009 Kernel Summit and Japan Linux Symposium). Anyone can stand for election by emailing as advised.

Clownix-spy. Vincent Perrier posted to announce a utility at clownix.net that can be used to plot any kernel variable changing over time through the use of a periodic kernel thread that wakes up to sample it and deliver the results to a userspace gtk-based plotting tool. The initial example is for plotting qdisc enqueus, dequeues, and drops.

URCU version 0.2. Mathieu Desnoyers posted version 0.2 of the userspace RCU library he has been working on. It contains some clarifications for three function usages.

The latest kernel release was 2.6.32-rc1|rc2 (both the same).

Greg Kroah-Hartman posted a series of review patches for the 2.6.27.36 stable kernel, and 136 review patches for the 2.6.31.2 stable kernel.

Rafael J. Wysocki posted a summary of regressions since the 2.6.31 kernel, based upon bug filings on the kernel.org bugzilla. As he notes, there aren’t too many new regressions since 2.6.31, but there are still “quite a number” since 2.6.30 and it’s been that way for quite some time.

Stephen Rothwell posted a linux-next tree for October 1st. Since Wednesday, the linux-next fixes tree still has a fix for powerpc/kvm, there is still a reverted SCSI commit, the sound tree gained a build failure (so the previous day’s version of that tree was used), the block tree lost its conflicts but gained a failure for which a commit was reverted, and the drm tree lost its conflict. The total subtree count remained steady at 139 trees.

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_20090930.mp3

From the Embedded Linux Conference in Grenoble, France, for September 30th, 2009, I’m Jon Masters with a summary of the day’s LKML traffic.

In today’s issue: dm-ioband, robust lists, and page writeback.

dm-ioband. Vivek Goyal posted anothe round of benchmarks of the dm-ioband patches, again noting some problems with the implementation. In the latest tests, he created two ioband devices (ioband1 and ioband2) of weight 100 each on two disk partitions. On one (ioband1), he had a buffered writer do writeup and on the other he had one priority 0 reader and an increasing number of priority 4 readers, to see how bandwidth distribution worked. With vanilla CFQ the results were roughly as expected, but the results for the dm-ioband patches had violently wild swings in bandwith and were quite clearly not correctly preserving any kind of fairness whatsoever. Ryo Tsuruta promised to look into it some more.

Robust Lists. The Linux kernel uses a “robust list” pointer in the task struct task representation structure in order to keep track of userspace futex locks – providing a flexible (and also extensible) way to keep track of locks that userspace might want to play with, and also an atomic means for it to do so through system calls that internally result in list ops. The kernel needs to specially handle the case of a new address space through execve, and Anirban Sinha was concerned that the code within exit_robust_list was inefficient.

Writeback. Fengguang Wu noted that WRITE_SYNC_PLUG and priotization of bio writeback had been implemented about 5 months ago due to complaints from Linus (so it’s no longer true that all requests get ultimately treated equally no matter their sync/async status). Fengguang also posted a patch increasing the MAX_WRITEBACK_PAGES size and adjusting the writeback call stack to support larger writeback chunks. The reason for a limit is to prevent holding I_SYNC against an inode for “enormous amounts of time”.

In today’s pull requests: some ext4 patches for 2.6.32 from Ted T’so, some nilfs2 fixes from Ryusuke Konishi, and some block updates for 2.6.32-rc from Jens Axboe (mostly driver fixes, and especialy to cciss) which included DRBD. Christoph Hellwig considered including DRBD to be ill advised at this stage.

In today’s miscellaneous items: a patch adjusting percpu initialization on IA64 such that the head.S provided __cpu0_per_cpu special CPU percpu area is copied over to a generic location in the linear mapping during memory initialization from Tejun Heo, a request from Amerigo Wang that Barry Song add a signed-off-by to his Y2K38 time patch, a connector bugfix from Christian Borntraeger, ongoing discussion of Intel’s TXT (Trusted eXecution Technology) and in particular Pavel Machek’s views on removal/modification of RAM chips at runtime to usurp any protections, a note from Frederic Weisbecker that patches against 2.6.29 (in this case against at the time experimental “perf” patches for ARM) are useless at this point as too much has changed and patches need to be against 2.6.32, a note from Jens Axboe that find_busiest_group uses a lot of CPU (multiple SSD testcases), a note from Florian Weimer that the new O_NODE open flag implementation does allow one to bypass permission checks on open files within directories whose permissions change while the file descriptor is open (and so “the whole thing is a bit worrisome because it may turn file descriptor information leaks into something worse”), a virtio_ids patch from Christian Borntraeger that makes Rusty’s previous cleanups (moving all device IDs into a single file) once again compatible with userspace users of the header files by moving some includes around, a note from Berthold Gunreben (who had previously posted about ATA bus errors on resume that Tejun Heo though were due to the PSU briefly dropping power to the disk – for which Tejun provided some detailed advice on burning aforementioned PSU) that he had moved to another filesystem (JFS) and could no longer reliably reproduce what might still exist as an underlying error, an RFC patch from Kamezawa Hiroyuki adding percpu array counter support (as used e.g. in vmstat) and new array_counter_add, and array_counter_read functions, a patch from Arjan van de Ven taking advantage of GCC’s ability to determine at compile time whether certain copy_from_user buffers are correctly sized to produce a compile-time (and not runtime) warning in the case that they are not, version 2 of some CFS hard limit patches from Bharata B Rao, a note that bluetooth “is very ill in -next” from Alan Cox, an update to Linus Torvald’s alternatives based cmpxchg64 with some fixes based on some actual testing from Arjan van de Ven, a patch ensuring we always return from cpu_idle with interrupts enabled from Kevin Hilman, and a note from Russell King that Linus imposes a “one pull request per week” limit on arch maintainers like himself and so this can explain why the ARM tree has been broken recently.

In today’s security items: An x86_64 patch from Jan Beulich removing a register leak situation in which a 32-bit process could temporarily switch itself into 64-bit mode in order to get access to additional 64-bit register entries that are not normally cleared on return to 32-bit userspace.

Finally today, Pavel Machek complained about Daniel Walker’s ongoing round of checkpatch warning emails, suggesting that they were “unwelcome” in the case that patches already had many other known problems to resolve.

The latest kernel release was 2.6.32-rc1/rc2 (both the same).

Stephen Rothwell posted a linux-next tree for September 30th. Since Tuesday, his “fixes” tree contains a build fix for powerpc/kvm, the usb.current tree lost all of its conflicts, the scsi tree commit that was causing boot failures was still reverted, the drm tree gained a conflict against Linus’ tree and the usb tree lost all of its conflicts. The total subtree count remained steady at 139 trees in the latest linux-next compose.

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

Folks,

I’m travelling to CELF Europe and will get the remainder of the updates out this weekend. I plan to spend hours in Paris finishing the transcripts on Sunday. Also, I strongly recommend in addition to backing up your data that you backup your settings more often My only 6 month old Hitachi HTS545032B9A300 randomly decided to give up on life yesterday, right before my trip. Putting it in the freezer helped marginally, but it will stop responding within 5 minutes of being attached…it’s dead. And it delayed the podcast catchup yet again.

Jon.

P.S. That would be why I’m behind replying to email.

Audio: COMING SOON

For Tuesday, September 29th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Consoles, IO bandwidth throttling, and VMI.

Consoles. Alan Stern raised the issue of console device naming, especially as pertains to removable devices, such as those using a USB interface. He feels that these devices should acquire a name (e.g. ttyUSB0 exposed through /dev/ttyUSB0) that the name should be persistent even beyond the device being removed from the system, and that the kernel should open each console device immediately upon it being registered as a console in order to prevent undelying data structures from being released upon device removal. He has raised this issue on several occasions prior to this. In response, Alan Cox posted how he had originally invesigned something like this could eventually be achieved (fixing the lifetime issue of console devices).

IO bandwidth throttling. Nauman Rafique posted to let Vivek Goyal (and everyone else) know that he and others had discussed the topic of Vivek’s IO controller patches with Jens Axboe at this year’s Linux Plumber’s Conference. In particular, they had discussed Jens’ concerns about the patch sizes, and the soft requirement that the patches work with all existing IO schedulers. Nauman proposes incremental addition of bits of the existing patches. Vivek is on board with just supporting CFQ initially if needed, but wonders whether this will really fly – in other words, whether the implementation shouldn’t be at a level above the IO scheduler (as favored by Andrew Morton). Jens Axboe concurred that he was not in favor of the direct expansion of the CFQ IO scheduler for this support because “some enterprise storages are better performed with NOOP rather than CFQ, and I think bandwidth control is needed much more for such storage system”. Jens suggests making throttling policy user selectable, at a higher layer, like IO scheduler selection today.

VMI. Ongoing discussion continued on the fate of VMWare’s VMI support in the kernel. This is a para-virtualization optimization that is no longer needed for performance reasons and will no longer be supported in future product releases from VMWare. But, as Peter Anvin, Gerd Hoffmann, and others had noted, there are many using VMI on existing systems so the code should not be “zapped” quite so quickly. Instead, Alok Kataria (of VMWare itself) suggested that the intention to remove support be noted in the feature-removal file and recommended that all distributions disable VMI going forward in order for seemless “Live Migration” to work for their customers and users. Arjan van de Ven took the opportunity to also note that vendors have a habbit of ignoring the “default” Kconfig options, so VMWare should not just assume that having an option disabled in Kconfig would automatically be picked up by Linux distros. Chris Wright liked the deprecation idea and suggested a runtime warning.

In today’s pull requests: some percpu fixes from Tejun Heo, some DRM updates from Dave Airlie (including support for video= KMS mode setting on the kernel command line) which were sent twice due to a missing subject on the first attempt, and some networking fixes from David Miller.

In today’s miscellaneous items: a note that the Vmalloc area figures in /proc/meminfo are correct (just refering to the theoretical address space of very many terrabytes) from Kamezawa Hiroyuki, another “lumpy” page writeback patch from Fengguang Wu, a trivial Intel TXT bug warning fix from Shane Wang, a series of hotplug and TSC cleanup patches for dynamic structure allocation and removal at KVM module load and unload from Zachary Amsden, some RCU patches from Paul E. McKenney simplifying rcu_barrier() with the goal of ensuring that offlined CPUs never have RCU callbacks queued, a vsprintf format string option for pretty-printing UUID and GUID values from Joe Perches, the latest version of the “permission masking security module” formerly known as “dpriv” from Andy Spencer, a fix for a mutex locking problem in a previous BKL (Big Kernel Lock) removal patch from Frederic Weisbecker, some fatfs-2.6 patches resent from Ogawa Hirofumi (who also replied to the “Simon and Garfunkel” corruption reported previously), some CPU affinity problems with KVM reported by Haneef Syed, some SCSI header cleanup patches from Michael S. Tsirkin, a suggestion from Arjan van de Ven that GFP_NOWAIT memory allocations are what one poster (who seemed to be partially re-implemeting “perf” due to being unaware of it) wanted in requesting ZONE_NORMAL allocations that might not be available immediately but without using a GFP_ATOMIC flag (which can cause system emergency pools to be used and exhausted and should not be used in general for large allocations), a NULL pointer fix in the swap core from Suresh Jayaraman, some NOHZ performance optimization patches from Martin Schwidefsky, some patches implementing full NAT support for IPVS from Hannes Eder, general discussion of multiple simultaneous port support in virtio_console, some connector permission checking patches from Philipp Reisner, ongoing discussion of Taro Okumichi’s dynamic kernel source browser, and a question from Robert P. J. Day as to whether he should modify his scripts that look for broken Kconfig references to also detect and inform the community about unreferenced header files throughout the kernel tree.

Finally today, a detailed analysis of a hard lockup and ext4 corruption from Ted T’so along with sympathy from Ted surrounding the experience (though of course he was in no way responsible for it). From the sound of it, Ted fingers hardware literally writing to the wrong location on disk (it was an USB drive of some kind according to the original poster, Andy Isaacson, who posted some dumpe2fs output online for Ted – and anyone else – to take a look at).

In today’s announcements: Userspace RCU. Mathieu Desnoyers followed up to previous discussion of the feasibility of a userspace RCU implementation (for doing RCU in application level code) with an implementation called “urcu”. He posted it on the LTTng website and says version 0.1 should work on both x86 32/64 and PowerPC. More information is at http://lttng.org/urcu.

The latest kernel release was 2.6.32-rc1 (remember that EXTRAVERSION unintentionally got set to “rc2″).

Eric Dumazet tracked down a problem in the cmpxchg() function, which doesn’t handle 64-bit values on X86_32 and doesn’t generate an error. He suggests either replacing a use of cmpxchg() in a problem-triggering patch from Peter Zijlstra with cmpchg64(), fixing xmpxchg() to handle 64-bit values, or reverting Peter’s patch. Linus noted the potential for “very nasty silent failure” and really wanted to fix use of cmpxchg() – even if it just generates a warning or link-time failure when used with 64-bit types. Arjan van de Ven suggested using the alternatives() implementation to patch according to the type of CPU found at runtime, for which Linus posted an “untested” patch.

Stephen Rothwell posted a linux-next tree for September 29th. Since Monday, the linux-next fixes tree still contains a powerpc/kvm fix, there is still a reverted scsi commit causing a build failure and there is still a removed patch that had caused various includes of autoconf.h to go away and break various people’s builds. So, very similar to the previous day’s tree. The total subtree count remained steady at 139 trees in Tuesday’s compose.

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

Audio: COMING SOON

For Monday, September 28th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: External process limits, page writeback, and QUEUE_FLAG_VIRT.

External process limits. Neil Horman posted a patch implementing a new procfs interface in /proc/pid/limits, allowing process limits to be set from outside of a running process. As Neil describes, modern tasks (also known as processes outside the kernel) can be long lived and it would be beneficial to be able to set limits without having to kill a task and restart it, just to set a limit. The new interface takes a simple format that can be written using the command line: “ “.

Page writeback. Discussion continued on the best practices for page writeback, or the handling of page of “dirty” memory containing data that needs to be committed back to disk. Specifically, the discussion centered around what priority “background” writes (the periodic writeback of dirty pages) should occur, and how this should contrast to synchronous writes being explicitly requested by a process performing an fsync. Fengguang Wu noted that, as things stand, the kernel makes no distinction for synchronous writes and the code path is still through balance_dirty_pages_ratelimited – Dave Chinner had advocated for differentiated handling between the two different cases by having the VFS layer cease “thow[ing]” away the necessary indication of whether an operation should be synchronous or asynchronous in nature.

This whole debate of course also relates to the wider ongoing issue of IO bandwidth management and the various patches proposed there, too. And on that particular note, Ryo Tsuruta and Vivek Goyal continue their back-and-forth on the relative merits of their differing approaches to the topic. That discussion included debate over fairness to rotational vs. SSD media. One set of patches proposed (by Corrado Zoccolo) would split out IO requests in three different queues (sync sequential, sync seeky, and async queues) which would then be handled alternatively in a round-robin fashion.

QUEUE_FLAG_VIRT. Rusty Russell requested the removal of the QUEUE_FLAG_VIRT patches, which had been intended to (within the context of virtio_blk) cause the immediate unplugging of the corresponding IO request queue, resulting in a lot of overhead on virtualized platforms such as KVM. Although Rusty could not reproduce the “extreme regressions” seen by some Fedora users, he nontheless wanted to remove the patches until such time as the virtio-blk overhead was low enough that this flag made sense (and then would be based upon some feature flag provided by the host kernel rather than being automatic).

In today’s pull requests: some parisc updates from Klye McMartin, some wireless fixes from John Linville, and some PM fixes for 2.6.32 from Rafael J. Wysocki.

In today’s miscellaneous items: a patch implementing support for limiting IRQ affinity to specific CPU domains from Dimitri Sivanich, a patch differentiating fake “injector” Machine Check Exceptions from the real deal so as to not confuse the handler when a real MCE occurs from Huang Ying (which inspired Hidetoshi Seto to post a 5 part patch series based upon it), a discussion of problems with non-atomic page flag motification in the HWPOISON (and other) patches from Fengguang Wu and Andi Kleen, ongoing discussion of how to handle the lack of additional bits in vm_area_struct, a patch moving common histogram functions for the “perf” utility into their own file from John Kacur, some permission elevation issues with the O_NODE open flag pointed out by Jamie Lokier, a patch from Frederic Weisbecker pushing the blk tracepoint calls further down the stack (to avoid ugly locking issues), a percpu trivial patch from Tejun Heo, the “final scan results” from Robert P. J. Day showing the bad Kconfig entries selecting non-existent variables, a confirmation from Martin Schwidefsky that an offending “sched_clock” Make it NMI safe” commit reported by Arjan van de Ven was causing problems on some x86_32 systems, some conspiracy theories surrounding the usurpation of Intel’s TXT (Trusted Execution Technlogy) by removing liquid nitrogen covered RAM sticks from a running system post S3 suspend and recovering the content, and a patch from Randy Dunlap expanding the recommended patch size limit in the SubmittingPatches documentation from it’s value of 40 kB (that was “so last millennium”) to the more respectable 300 kB size we tend to see today.

Finally today, Barry Song posted a patch intended to help toward the Y2K38 problem – the date at which the UNIX 32-bit time_t will overflow (and the entire world will end, at least in the eyes of the media – can you imagine what CNN and Faux News types would do with 3-D holographic TVs showing red neon effects with dire warnings of impending doom in 2038?).

In today’s announcements: Taro Okumichi announced that he had written a “gcc-tracer” and “html-formatter” that could be used to browse kernel source code (currently only init/main.c). I haven’t looked to see how this differs from what LXR has been able to do forever.

The latest kernel release was 2.6.32-rc1. As mentioned by a number of people, Linus had accidentally set the EXTRAVERSION in the kernel Makefile to “-rc2″. In his typical self-deprecating manner, Linus refered to himself as a “moron” and said he’d “try not to do that again”. But he also noted that the git tags were actually correct (so it shouldn’t be too confusing to the history). For his part, Stephen Rothwell noted that he wouldn’t be applying a patch to linux-next to set it to -rc1 in order to ensure all bug reports are “consistently confusing ”.

Frans Pop noted some weird vmalloc numbers in /proc/meminfo and asked: “is it me or are VmallocTotal and VmallocChunk off by a factor of 10,000 or so?”.

Eric Dumazet noted some very unusual process time accounting behavior in 2.6.32-rc1. He posted a reproducer program source file. Linus pointed the finger at some of the usual suspects in noting that overall process times were accurate, but somewhere along the line stats for individual tasks were not.

Michael Tokarev noted some issues on Pentium III systems running 2.6.31. He found that a “real PIII” machine had no problems booting, whereas “pretty consistent[ly]” the machine would hang on boot with an Intel PIII Celeron. He noted that the cpu flags differed between the two in that the Celeron did not list the “apic” flag, even though APIC support was enabled in his config.

Pavel Machek reported a problem with the behavior of CROSS_COMPILE, especially when using ccache. The error message refered to running “make mrproper”, which it also broke, and had a typo in the message itself. “Ouch”, indeed.

Stephen Rothwell posted a linux-next tree for September 28th. Since Sunday, the fixes tree for linux-next had a build fix for powerpc/kvm, a scsi commit causing boot failures got reverted and a patch removing various includes of autoconf.h that caused subsequent build failures was also removed. The total subtree count remained steady at 139 trees in the Monday compose.

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

Audio: COMING SOON

For the weekend of September 27th, 2009, I’m Jon Masters with a summary of the weekend’s LKML traffic.

In today’s issue: CFS vs. BFS, Performance Events, (a) Shortage of flags, and Tree Scanning.

CFS vs. BFS. Takeuchi Satoru posted a comparitve analysis of the BFS and CFS algorithms, using a benchmark known as “massive_intr” (intended to measure a scheduler’s fairness and overall throughput). The kernels used were a vanilla 2.6.31, 2.6.31-bfs211 (BFS) and 2.6.31-edf (the latest Linus tree with the new EDF patch applied). The tests found that both CFS and BFS “look good”. CFS had better fairness (which isn’t surprising), while BFS had better throughput (which is perhaps not too surprising either). EDF seemed a little immature for producing real benchmarks. Takeuchi notes that the slight difference in kernel means that this isn’t entirely an Apples to Apples comparison. The results are fairly interesting, providing a good case for BFS on the kinds of hardware that this test was run on (a laptop machine with a dual core x86_64 CPU). What remains to be seen is how well BFS performs on a much more scaled system.

Performance Events. Arjan van de Ven posted an RFC patch implementing an kernel-internal interface to performance counters, citing that there “are reasons for kernel code to ask for, and use, performance counters. For example, in CPU freq governors this tends to be a good idea, but there are other examples possible as well of course”. The patch adds the necessary bits, which an experimental cpufreq driver that Arjan is working on is currently making use of (this being the reason for the patch existing in the first instance).

Shortage of flags. Nigel Cunningham had previously noted that the vm_flags field within VMA structures had run out of space for an additional flag that would be required by the TuxOnIce alternative suspend/resume code. He had made various suggestions, which had culminated previously in Kamezawa Hiroyuki suggesting that an additional vm_flags2 be created. Kamezawa added that little used flags in vm_flags could be migrated over to vm_flags2 in order to avoid any real performance hit in making such changes, to which Nigel added his hearty concurrence with the idea.

Tree scanning. Robert P. J. Day posted seeking advice concerning his tree scanning scripts that he uses (post merge-window closure) to detect unused and incorrectly referenced Kconfig CONFIG variables in the wild. He would like to know where to put the output, and the best form in which to share results, which are currently on a separate website (the idea being that he pokes subsystem maintainers individually to fix their own problems currently). Separately, Robert announced that he had updated a wiki page of “unused(?)” CONFIG variables that he would like people to take a look at.

In the weekend’s pull requests: some powerpc bits for 2.6.32 from Ben Herrenschmidt (including some performance “nits” from Anton Blanchard), part 2 of some sh updates for 2.6.32-rc1 from Paul Mundt, some networking updates from David Miller (including fixing CONFIG_NET=n on some platforms, and a large number of other fixes besides), some watchdog patches from Wim Van Sebroeck, some fatfs-2.6 patches from Ogawa Hirofumi, a round of writeback updates for 2.6.31-rc1 from Jens Axboe, a second batch of kbuild updates for 2.6.32 from Sam Ravnborg, some fixes for Alpha and MIPS from Sam Ravnborg, some SPARC and networking updates for 2.6.32 from David Miller, a single writeback fixup from Jens Axboe, some x86, tracing, perf events, and futex fixes for 2.6.32 from Ingo Molnar, some backlight and LED updates from Richard Purdie, part 3 of some ACPI patches for 2.6.32 from Len Brown, and some i2c updates for 2.6.32 from Jean Delvare.

In the weekend’s miscellaneous items: some KVM hotplug patches from Zachary Amsden (supporting CPU hotplug – his 5th of the 5 patches is amusingly entitled “Math is hard; let’s do some cooking”, and who wouldn’t agree?), a question concerning how git really handles merge conflict resolution from Joe Perches (who was trying to figure out a problem merging MAINTAINERS fixes), a fix for the case of CONFIG_KALLSYMS being disabled from Paul Mundt, a fix to sscanf format handling from Andy Spencer, a patch correcting ARCH=x86 from Peter Anvin (which he said he “could have sworn” he had tested previously before it started breaking, something he said might be a toolchain issue), ongoing discussion of the eventual unification of the various in-kernel RAID efforts, ongoing discussion of “immediate values” and jumps, ongoing discussion of the relative merits of various IO bandwidth controlling patches and their impact upon rotational media, some tracing/kprobes updates from Masami Hiramatsu, an RFC patch series implementing a new “perf kprobe” command allowing one to control kprobes using the “performance events” “perf” utility from Masami Hiramatsu, a fix to undo massive breakage of “the vast majority of ARM systems in the wild which are still pre ARMv6″ from Nicolas Pitre, a patch from Fengguang Wu removing the “unsafe” use of __set_page_locked in the HWPOISON code, a reported issues with e1000e jumbo frames no longer working in 2.6.31 from “Nix”, some patches intended to make copy_from_user to a stack slot provably right from Arjan van de Ven (taking advantage of a GCC feature), a patch removing USE_ELF_CORE_DUMP (which is defined everywhere but on the Microblaze architecture, for which he deems Microblaze to be at fault) from Christoph Hellwig, a patch removing some overhead from /proc/net/tcp from Yakov Lerner, and a question about section mismatches from Russell King.

Finally today, have you ever stopped to really look at the mail clients in use by folks posting to the LKML? I do. Surprisingly, a large number of patches are sent by Thunderbird running on Windows systems. An interesting fact. There are even still a few Microsoft LookOut users floating around posting bits.

In the weekend’s announcements: Linux 2.6.32-rc1. To great fanfare, Linus Torvalds announced the release of 2.6.32-rc1 of the Linux kernel on Sunday afternoon at 15:34 Best Coast Time (PDT). He cited LinuxCon and Plumbers amongst the reasons why the merge window had been somewhat extended. The latest kernel contains 67% driver updates, for a change doesn’t include a new filesystem, and does have the usual range of “interesting changes” (including the fact that “ZERO_PAGE is back!”). Linus encourages everyone to “Go wild, test it out, and let us know about any regressions you find”.

Sysprof 1.1.2. Soeren Sandmann announced release 1.1.2 of his “sysprof” system-wide CPU profiler for Linux. This version is based upon the “performance counters” interface that was introduced in kernel 2.6.31. As he notes, 1.1.2 is a development release and will not work with kernels prior to 2.6.31 due to the switch to performance events.

Linux-RT for Debian. Pengutronix announced that they have started providing the Realtime Preemption Linux kernel patches in the form of Debian packages. They timed the announcement to co-incide with the “RT” workshop in Dresden [which LWN already has an excellent writeup of at this point in time]. For further information, you can refer to the Pengutronix website announcement: www.pengutronix.de/software/linux-rt/debian_en.html.

The latest kernel release was 2.6.31.

Andrew Morton released an mm-of-the-moment for 2009-09-25-14-35.

Peter Volkov posted a couple of patches that he believes had been missed from the 2.6.31.1 stable kernel. Tejun Heo reported a race bug in get_device_parent which he said was being caused by sysfs creating several devices in the “cuse” class concurrently and with CONFIG_SYSFS_DEPRECATED disabled. Zdenek Kabelac reported an NFS problem with the 2.6.31 git tree running as a qemu guest. Philippe De Muyter reported some issues reading particular Simon and Garfunkel music [let's face it, this is a pretty serious regression compared with being unable to read Britney Spears or Lady Gaga] files using the Linux vfat implementation when the file ended in more than one “dot” (US: “period”) – he attached a patch. Aneurin Price noted that kernels since 2.6.26 had been “unusably slow” for him and that he tracked it down to an MTRR patch. Rafael J. Wysocki noted that a 2.6.31 git commit to the tty code had broken resume from hibernation on his MSI Wind U100 system. Ted T’so bisected a regression affecting his T400 system in which the second suspend/resume operation after the first was bound to fail – he listed the offending merge commit. Con Kolivas reported some stack corruption on 2.6.31 using KVM.

Stephen Rothwell posted a linux-next tree for September 25th. In announcing today’s compose, Stephen enclosed a “diffstat” that shows 886 files changed, 114306 insertions, and 17547 deletions, which he suggested implied that “we are nearly done for -rc1″. Since Thursday, his fixes tree contains a build fix for powerpc/kvm, the cifs tree gained a couple of build failures and the tip tree lost its conflict. Stephen notes that we continue to see issues bouncing from one tree to another as Linus continues his merging in earnest. The total subtree count remains at 139 trees in the Friday linux-next compose.

Stephen Rothwell also posted (unusually) a linux-next tree for Saturday. Since Friday, his fixes tree still contains the build fix for powerpc/kvm, the sparc-current, and acpi trees gained issues, while the arm-current, net-current, and cifs trees lost their issues. Conflicts continue to bounce from one (sub-) tree to another and the total tree count remains at 139 trees in the Saturday linux-next compose.

Stephen Rothwell also posted (extremely unusually!) a linux-next tree for Sunday. Since Saturday, his fixes tree still contains a build fix for powerpc/kvm, the sparc-current, acpi, and backlight trees lost their issues, while he added a patch to remove includes of autoconf.h that had been causing some build failures. As before, Stephen notes that conflicts continue to bounce between trees as Linus continues with his ongoing merging. The sub-tree count remained steady at 139 trees in the latest compose.

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

Audio: COMING SOON

For Thursday, September 24th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Checkpoint and restart, ksplice, and RAID.

Checkpoint and restart. Oren Laadan posted 80(!) patches implementing the latest “checkpoint and restart” code for the Linux kernel. The first 17 patches are cleanups, patch 18 adds the new system calls, while the remainder contain the actual “checkpoint and restart” (also refered to as “c/r”) code. Patch 32 contains an implementation for “deferqueue”, which is similar to workqueues but allows a process to defer work that will run in the original context of the task that scheduled it. So far, the code can checkpoint and restart interactive sessions of “screen” across a kernel reboot, which is useful for testing, but a far cry from a full implementation useful for the majority of users.

Ksplice. Tim Abbott (ksplice author extrodinaire) and Christoph Hellwig had a back and forth concerning the (currently) out-of-tree ksplice use of the each_symbol export, which was apparently originally exported for use by ksplice. A recent patch (part 3 of a 4 part patch series) from Christoph had removed that export (it was entitled “module: unexport each_symbol()) and Tim would really have prefered that it stick around. In response, Christoph sent a one line reply: “We don’t keep symbols for out of tree junk around.” Rusty Russell (the in-kernel module loader infrastructure maintainer) stated that he had expected ksplice to go in earlier and had originally applied the patch to make life easier for the eventual merge. But, in his words, “it’s a big hunk of code” [so it might not get merged in the 2.6.32 timeframe, either]. Separately, Tim sent some more linker script cleanups for ksplice preparation.

RAID. Discussion continued (in the thread entitled: “DRBD for 2.6.32″) concerning the eventual removal of the older “md” code once unification between the various in-kernel (md/dm) RAID implementations is complete. Neil Brown thought this process ought to take about 3-5 years, given the average time frame for “enterprise” releases of the kernel. Neil also suggested that the unification effort hadn’t really gotten under way yet, that there was little notion of what shape such an implementation might take, and that it might make more sense to spend time discussing that than the relative merits of merging DRBD into the 2.6.32 kernel. Fujita Tomonori pointed out some previous comments (from Christoph Hellwig) on what a new userspace visible API for RAID management might look like, on the DRBD development list.

In today’s pull requests: some bugfixes for the security subsystem from James Morris, round 2 of some hwmon updates for 2.6.32 from Jean Delvare, some md updates for 2.6.32 from Neil Brown (essentiall a ping reminder to pull), some microblaze fixes for 2.6.32 from Michal Simek, an update to the cputime tree maintained by Martin Schwidefsky (correcting the format of /proc/uptime), some module and parameter updates for 2.6.32 from Rusty Russell, some btrfs updates for 2.6.32 from Chris Mason (including various work on snapshot and subvolume deletion from Yan Zheng – and the btrfs worker threads are now more dynamic as they will die in order to be later respawned if they are not used for a while), some drm-intel updates for 2.6.32 from Eric Anholt, some MAINTAINERS cleanups from Joe Perches, some infiniband updates from Roland Dreier, version 2 of tracepoints for uses of the BKL (Big Kernel Lock) useful in detecting and removing such uses as the BKL is slowly being removed from Frederic Weisbecker (to which Ingo Molnar later noted some build problems), some cris updates for 2.6.32 from Jesper Nilsson, and some eCryptfs fixes for 2.6.32 from Tyler Hicks.

In today’s miscellaneous items: a patch reducing the overly excessive (one per CPU) “TSC is reliable” and “PAT enabled” messages on boot from Rolan Dreier, an assertion that a previous module loader fix in the usermodehelper code from Neil Horman had been incorrect and was causing another backtrace from Sebastian Andrzej Siewior (he included a replacement patch, which Neil agreed was actually the correct fix), some documentation updates for cgroups tasks and procs files from Paul Menage, some cpumask conversions and obsolescence removal patches from Rusty Russell, a suggestion from Kamezawa Hiroyuki that a new vma->vm_flags2 might be required for the overflow from vm_flags becoming full (in reply to the desire fro, Nigel Cunningham to have some room for TuxOnIce to make use of an additional bit for a status flag), some KVM patches from Zachary Amsden (moving timer initialization into an independent function), a patch from Peter Williams (following up to the previous day’s discussions with Peter Zijlstra on the topic) setting the correct normal_prio and prio values in sched_fork() (fixing some issues where some paths through sched_fork() would ignore this requirement and removing the need for a call to effective_prio() in wake_up_new_task()), a page writeback patch from Shaohua Li that effectively reconciles inode commits from the same filesystem so that they will be written together and reduce rotational media head movement (which was deemed a “Good idea!” by Fengguang Wu and immediately signed off on), an optimization removing an unnecessary call to wbinvd on Intel MP CPUs that support a C3 share cache when entering an C3 ACPI power state, an RFC patch series updating autofs4 to deal with some VFS locking changes from Ian Kent, some AMD64 EDAC fixes from Borislav Petkov, some percpu patches making allocation failure warnings more verbose from Tejun Heo, a patch fixing a buffer allocation problem in the “perf” tools from Eric Dumazet, some “immediate values” patches from Mathieu Desnoyers intending to take advantage of data-cache optimization (to which Jason Baron replied that his alternative “jump label” infrastructure had already been proposed, although Jason seemed to favor various aspects of Mathieu’s patch), a patch allowing “perf timechart” to output only power mode information from Arjan van de Ven, version 7 of the new “clone2″ system call intended to better support checkpoint and restart from Sukadev Bhattiprolu, some memory barrier commentary in the futex_wait_queue_me code from Darren Hart, version 10 of the “IO scheduler based IO controller” patches from Vivek Goyal, another round of “jump label” patches from Jason Baron (obviously prompted by Matheiu Desnoyers’ earlier posting of a – related – “immedate values” implementation), and a note from David Miller that “what’s really sad is that you [refering to Ingo Molnar] don’t attend enough conferences so that you can meet face to face with people and you (and others) would as a result avoid many unnecessary heated discussions as a result” [in the spirit of not becoming the Us Weekly of kernel traffic, I'll leave the rest of the discussion up to you to read].

Finally today, Steven Rostedt (and various others) had a somewhat lengthy discussion about the correct English (grammar) for refering to a mailing list intended for the discussion of user issues pertaining to tracing. Steven’s comment becomes the quote of the day: “Oh God, Linux is now tracing its users, but I don’t want to be traced!”.

In today’s announcements: Greg Kroah-Hartman announced the release of stable kernels 2.6.27.35, 2.6.30.8, and 2.6.31.1. He strongly encourages users of these stable kernels to upgrade.

The latest kernel release was 2.6.31.

Ingo Molnar reported a crash in the -tip tree in ibm_find_acpi_device. Daniel J. Blueman reported an NFS suspend to RAM hang when using an NFS home directory (including the full oops report) on recent kernels. Ed Tomlinson reported a “strange” ATA related freeze with 2.6.31.1-rc1.

Stephen Rothwell posted a linux-next tree for September 24th (a little later than usual). Since Wednesday, the drbd tree has been undropped, the tip tree gained a conflict, the ocfs2, jdelvare-hwmon, block, drbd, battery, and usb lost their conflicts, and Stephen applied a patch for a build failure in Linus’ git tree. The total subtree count is reported as falling to 139 in the latest compose (although that again seems a little out-of-sync). Stephen reminds everyone not to push for 2.6.33 until 2.6.32-rc1 is out.

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

Audio: COMING SOON

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

In today’s issue: Modules, dpriv, and running out of space in vm_flags.

Modules. Alan Jenkins and Rusty Russell discussed Alan’s previous patches that would sort the kernel built-in symbol map so that it could be binary searched at module load and dynamic linking time. Rusty thought it might be easier to sort the in-kernel symbols on boot, but Alan pointed out that this could add as much as 7ms to system boot times as “pure overhead” (in his hacked up prototype), and so for this (and other reasons) continues to favor having the kernel symbols be sorted at build time. The module loader will then have a much easier time resolving symbols and more quickly linking modules later. Separately, Tim Abbott sent Alan (and everyone else) an initial lib/bsearch.c patch implementing a generic binary search function for the kernel since “there a[re] a large number [of] hand-code binary searches in the kernel…[and] getting binary searches right is difficult”.

A Privilege dropping security module. Andy Spencer posted to let everyone know that he was working on a new LSM (Linux Security Module) called dpriv. This module (which can be used by any user, not just root) creates a dynamic runtime “policy” that does not implement MAC (Mandatory Access Control) but instead can be used simply to drop specific access rights at runtime. As an example, Andrew shows how one can cause the permissions on the root filesystem to be dropped by writing into /sys/kernel/security/dpriv/stage (followed by writting a “commit” into the /sys/kernel/security/dpriv/control “file”). Currently, only file permissions can be controlled using “dpriv”, and its author would like to know what you think about it.

Out of space in vm_flags. Nigel Cunningham posted asking for advice now that the new VM_MERGEABLE flag in post-2.6.31 has taken the last bit in vm_flags. Nigel has some code in his alternative suspend framework (TuxOnIce) that needs a bit too, which could be solved by adding a new long, but at least one kernel function is being passed the flags value directly and so would need to have its prototype and behavior changed.

In today’s pull requests: some tracing fixes for -tip from Frederic Weisbecker, “two radeon fixes” in the DRM tree from Dave Airlie, some input updates for 2.6.32 from Dmitry Torokhov, some S+Core patches for 2.6.32 from Liqin Chen, round 2 of OCFS2 changes for 2.6.32 (with the reflink() system call removed for the moment to avoid contention) from Joel Becker, some writeback fixes for 2.6.32 from Fengguang Wu, some lguest and virtio fixes for 2.6.32 from Rusty Russell, some USB patches for 2.6.32 from Greg Kroah-Hartman (containing “lots of usb stuff all over the map”), some wireless updates from John Linville, some plan9 filesystem changes for 2.6.32-rc1 from Eric Van Hensbergen, and some NFS client cleanups and bugfixes from Trond Myklebust.

In today’s miscellaneous items: a kmemleak fix from Roland McGrath, version 2 of a patchset convering IA64 over to dynamic per-cpu from Tejun Heo, a patch cleaning up orig_ax handling in getreg() (for e.g. ptrace/core-dump fetches) from Roland McGrath, a patch implementing the previously discussed TRACE_EVENT_ABI (using some suitably cunning macros) from Steven Rostedt by way of Arjan van de Ven, a suggestion that (after 10 years) it might be about time to remove the gcc option “-Wdeclaration-after-statement” since C99 has been around long enough at this point from Amerigo Wang, a patch adding a generic method of sending quota message warnings to userspace from Steven Whitehouse (for non-dqout filesystem use), some memory leak fixes from Jiri Slaby, a patch changing the kernel side of the sys_truncare/sys_ftruncate system calls to avoid what he deems a needless unsigned->signed->unsigned conversion cycle from Heiko Carstens, an RFC userspace RCU implementation from Mathieu Desnoyers “(ab)using futexes to save cpu cycles and energy”, and a patch changing some KSM defaults to “better fit into mainline kernel” now that KSM is in the mainline tree from Izik Eidus.

In today’s announcements: linux-trace-users. David Miller noted that he has created the linux-trace-users mailing list on vger.kernel.org (in reply to Steven Rostedt) for discussion of user issues relating to tracing and the various tracing tools.

SystemTAP 1.0. Josh Stone announce the (very long anticipated) 1.0 release of SystemTAP. This release features experimental support for unprivileged users, cross-compiling for foreign architectures (which gdb has supported forever), and a lot more besides.

The latest kernel release was 2.6.31.

Chris Malley was experiencing machine hangs when using “perf sched record” for which a patch from Peter Zijlstra did not seem to make a difference.

Stephen Rothwell posted a linux-next tree for September 23rd. Since Friday, the ocfs2, jdelvare-hwmon, block and usb trees gained problems, while the input-current and rr trees lost theirs and the kmemcheck tree needed an “obvious fix”. The drbd tree was dropped due to a build problem. The total sub-tree count is listed as 140, but does not seem to account for the tree that was removed in the compose. Stephen reminds everyone not to begin pushing patches for 2.6.33 until 2.6.32-rc1 has been released, and also reminds everyone that conflicts are bouncing between trees as Linus merges.

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

Audio: COMING SOON

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

In today’s issue: Fanotify, and modules.

NOTE: Several kernel hackers were at or en route to LPC (Linux Plumbers Conference) and so the traffic volumes were affected.

Fanotify. Fanotify is a new framework originally authored by Eric Paris (thanks a lot!) in order to help “anti”-malware vendors intercept and authorize certain file operations on the fly, using a generic interface. But fanotify is intended to be useful for other purposes, as Jamie Lokier pointed out (at the same time as re-affirming his total lack of interest in malware scanning uses thereof) was his reason for “sticking his oar” in recently. He is keen to see non-malware uses (improved inotify and other userspace indexing services, such as update) work out right. Davie Libenzi wondered whether, since the malware scanners generally favor “hacking” the syscall table, Linux should just provide a “non racy” mechanism for interrupting and monitoring system calls as some kind of ptrace-on-steriods perhaps. Argument continued on this and many other topics, including whether literal pathnames were important or whether on-access scanning tools should have to look them up if they care, and on whether ioctls or “idiotic packet interfaces” like netlink were best.

Modules. Alan Jenkins posted some module patches intending to speed up symbol resolution during load. The current Linux module implementation has modprobe (or perhaps insmod, if modprobe is not being used) simply load an ELF image containing a number of sections that the kernel will then link itself (in contrast to the old days, when it was all linked in userspace). Alan’s patches sort the tables of builtin kernel symbols so that the module loader can resolve against them using a standard binary search at load time. Using these patches, Alan has elimated 20% of the CPU cycles and 0.3 seconds of real time for a system boot on his EeePC 701 system. Kudos to Alan, once again.

In today’s pull requests: some kmemcheck updates from Vegard Nossum, some tracing/workqueue fixes from Anton Blanchard, another round of RFC patch from Zhang Rui implementing the ALS (”Ambient Light Sensor”) sysfs class driver, version 4 of his “compcache” compressed swap patches from Nitin Gupta, some performance counters (”performance events”) fixes from Ingo Molnar, some timer updates from Thomas Gleixner, some tracing/kprobes updates from Frederic Weisbecker, some s390 patches from Martin Schwidefsky, some sound patches from Takashi Iwai, and some regulator patches for 2.6.32 from Liam Girdwood.

In today’s miscellaneous items: some performance events fixes for powerpc from Paul Mackerras, an endorsement for a dedicated tracing mailing list from Li Zefan and Avi Kivity (both in reply to Steven Rostedt, Avi kicking things off with an initial question to boot), some futex cleanups (and also a race fix) from Darren Hart, version 5 of the RFC cpuidle POWER infrastructure patches intended to allow flexible management of idle policy from Arun R Bharadwaj, a “philosophical” question concerning which of two uaccess.h (linux or asm) headers should be included from Robert P. J. Day, some S+Core patches from Liqin Chen (including header files in that architecture’s linker script), an MCE error injection fix in the face of real errors from Huang Ying, a patch implementing a new “kcoredump” module that uses kprobes to perform a kernel “core dump” anywhere within the kernel (not as in the existing implementation of /proc/kcore) from Hui Zhu, another RFC patch implementing a SCHED_EDF (”Earliest Deadline First”) scheduler from “Raistlin”, version 3 of his RFC SLBQ on memoryless node configurations patches from Mel Gorman, some further linker script cleanup patches (facilitating ksplice integration) from Tim Abbott, an admission that once all other users of CONFIG_PARAVIRT are gone even lguest may not be enough to keep it around(!) from Rusty Russell, and patches containing the latest implementation of the Ceph distributed filesystem client from Sage Weil.

The latest kernel release was 2.6.31.

Shaohua Li reported a regression in page writeback statistics on a test system featuring 12 disks in kernels after a specific commit, but could not figure out an immediate fix for the issue, and so sought further comments. Xiaotian Feng reported a problem running “startx” to start an X session on the latest git tree, attributing it to an issue with KMS on a Fedora 11 system (to which Peter Zijlstra suggested either disabling KMS or updating the Fedora system). Darren Hart reported that he is hitting a repeating BUG on boot on his Thinkpad T60p when running the latest 2.6.31-rt11 preempt-rt kernel (which Clark Williams thinks he saw previously but thought was fixed now – and so Clark requested that Darren send him his kconfig to verify).

Stephen Rothwell announced that there would also not be a linux-next release for September 22nd – he was still feeling under the weather.

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