The current 2.6 kernel prepatch is 2.6.8-rc2
, which was
by Linus just prior to
heading off to Ottawa. Changes this time include another big set of
"sparse" annotations, a USB update, and lots of fixes; see the long-format changelog
for the details.
Linus's BitKeeper repository has acquired no patches since 2.6.8-rc2.
There have also been no new -mm releases in the last week; expect the process to remain
stopped for a few days until OLS is done. Thereafter, expect a large flood
of patches as various developers test the limits of the new development
process, which states that more intrusive patches are welcome in 2.6.
The current 2.4 prepatch remains 2.4.27-rc3; Marcelo has released no
patches since July 3.
Comments (1 posted)
Kernel development news
The 2004 Kernel Summit was scheduled for July 19 and 20, immediately prior
to the Ottawa Linux Symposium. For those who are interested, the advance agenda
LWN editor Jonathan Corbet was a member of the program committee and
attended the event; the following is his report.
Monday got off to a bit of a slow start; it seems that some of the
developers may have enjoyed themselves a bit too much at the opening dinner
the night before. Summit attendees also had a serious problem: ISP
troubles keep the wireless network down all day, so there was little
alternative to actually listening to the ongoing sessions. That said, a
constructive set of discussions was held with little overt disagreement
among the participants.
Monday's sessions include:
- The processor panel. Engineers from
Intel, AMD, and IBM discussed where their architectures are going and
the implications for the Linux kernel.
- Virtual memory, with special attention
to the topics of NUMA support, hotpluggable memory, and page
- Software suspend; what will it take
before we can reliably suspend and restore our systems?
- Kobjects and sysfs, and what needs to
be done to get the developers to complain about them less in 2.7.
- Video drivers, featuring a cameo
appearance by Keith Packard.
- Desktop performance. Robert Love led a
discussion on how the Linux kernel can better support desktop
- Short topics, being an opportunity for
developers to present an interesting issue in five minutes.
Tuesday's coverage is now complete. This long day was set aside for a wide
range of topics, from customer experiences to clustering, to the
development process. The individual sessions were:
- The customer panel was a discussion led
by technical managers from Goldman Sachs and Amazon.com; they talked
about the problems they have with Linux and how the kernel could
better support their needs.
- Clustered storage and just what
capabilities need to go into the kernel to support this feature.
- Kexec and fast booting; what is
required to make the Linux kernel boot in a reasonable period of time?
- RAS tools, with an emphasis on simple
tools to help track down kernel reliability problems.
- Networking summit summary. One week
prior to the kernel summit, a small group got together in Oregon for a
two-day networking summit. Stephen
Hemminger summarized the results for the kernel group.
- Asynchronous I/O; a session on what
is required to make AIO work properly under Linux, and whether it is
- Multipath I/O and device mapper issues.
- Virtualization, running virtual
machines under (and on top of) Linux.
- Security. Linux has acquired a great
many security features over the last few years; what other work is
required in that area?
- Class-based Kernel Resource
- OSDL relations. How does the Open
Source Development Labs relate with the development community, and
how can that relationship be improved?
- The final session was about the
development process; have a look to see what was said about when the
2.7 development series will begin - the answer is not quite what one
Comments (none posted)
Software suspend has long been one of the problem areas in the Linux
kernel. Despite multiple available implementations, truly reliable,
out-of-the-box support for suspending a system to disk and (crucially)
restoring it again is still missing. The return of one long-missing
developer may help to improve things, however.
Pat Mochel is the author of much of the power management and device model
code in the 2.6 kernel. At one point in his efforts, his communications
with software suspend ("swsusp") maintainer Pavel Machek broke down. In response,
Patrick created his own fork of the software suspend code, which he called
"pmdisk." The pmdisk code went into the kernel, and a small amount of work
was done on it, but then Pat got busy with other things and vanished from
the kernel development community. Nobody else was working on pmdisk, so
the effort simply stalled. Pavel has discussed its removal from the kernel
more than once, but that has not ever happened.
Just in time for the Kernel Summit, Pat returned with a 25-part patch set. Pat now believes that he
made a mistake by forking the software suspend code, and is trying to make
up. So his patch set removes pmdisk from the 2.6 kernel - but not before
merging its best parts into the existing swsusp code base. With this patch
set, swsusp is significantly cleaned up and more firmly integrated into the
kernel's power management subsystem. This code base, Pat hopes, will prove
a good starting place for further work toward respectable software suspend
There is one other player in this game, however: the swsusp2 work done by
Nigel Cunningham and others. This code, which forked from swsusp some time
ago, exists as a out-of-tree patch. It is, however, by many accounts, the
most featureful and reliable software suspend implementation available for
Linux. Swsusp2 offers a more polished display, the ability to abort the
suspend operation, and more. Nigel has recently been making noises about
trying to merge swsusp2 into the 2.6 mainline.
The last time this topic came up, there was a significant amount of
resistance. All versions of swsusp feature a "refrigerator," which is a
mechanism for cooling off all processes in the system before suspending the
system itself. The swsusp2 refrigerator has seen significant amounts of
work intended to keep the system from refrigerating processes which might
still be needed by other parts of the system before it is suspended. The
result is a large number of macro calls interspersed through the rest of
the kernel marking places where a process should not be refrigerated.
These changes make the swsusp2 patch relatively intrusive; they also create
a new kind of critical section within the kernel which looks hard to
maintain over the long run.
The current feeling, as reflected at the kernel summit, is that much of
Nigel's work cannot be merged in its current form. It also needs to be
split into a set of small, incremental patches before it can be
considered. Hopefully this work will happen, however; swsusp2 has things
to offer. If its best features can be merged in with swsusp, perhaps the
kernel may yet move from three unreliable software suspend implementations
to a single version which actually works.
Comments (8 posted)
Patches and updates
Core kernel code
Filesystems and block I/O
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