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3.12 merge window, part 2
By Jonathan Corbet September 11, 2013
As of this writing, nearly 8,500 non-merge changesets have been pulled into
the mainline repository for the 3.12 development cycle; almost 5,000 of
those have been pulled since last week's
summary. The process was slowed
somewhat when Linus's primary disk drive failed, but not even hardware
failure can stop the kernel process for long.
This development cycle continues to feature a large range of internal
improvements and relatively few exciting new features. Some of the
user-visible changes that have been merged include:
- The direct rendering graphics layer has gained the concept of "render
nodes," which separate the rendering of graphics from modesetting and
other display control; the "big three" graphics drivers all support
this concept. See this
post from David Herrmann for more information on where this work
is going.
- The netfilter subsystem supports a new "SYNPROXY" target that
simulates connection establishment on one side of the firewall before
actually establishing the connection on the other. It can be thought
of as a way of implementing SYN cookies at the perimeter, preventing
spurious connection attempts from traversing the firewall.
- The TSO sizing patches and FQ
scheduler have been merged. TSO sizing helps to eliminate bursty
traffic when TCP segmentation offload is being used, while FQ provides
a simple fair-queuing discipline for traffic transiting through the
system.
- The ext3 filesystem has a new journal_path= mount option that
allows the specification of an external journal's location using a
device path name.
- The Tile architecture has gained support for ftrace, kprobes, and full
kernel preemption. Also, support for the old TILE64 CPU has been
removed.
- The xfs filesystem is finally able to support user namespaces. The
addition of this support should make it easier for distributors to
enable the user namespace feature, should they feel at ease with the
security implications of such a move.
- Mainline support for ARM "big.LITTLE" systems is getting closer; 3.12
will include a new cpuidle driver that builds on the multi-cluster power management patches to
provide CPU idle support on big.LITTLE systems.
- The MD RAID5 implementation is now multithreaded, increasing its
maximum I/O rates when dealing with fast drives.
- The device mapper has a new statistics module that can track I/O
activity over a range of blocks on a DM device. See Documentation/device-mapper/statistics.txt
for details.
- The device tree code now feeds the entire flattened device tree text
into the random number pool in an attempt to increase the amount of
entropy available at early boot. It is not clear at this point how
much benefit is gained, since device trees are mostly or entirely
identical for a given class of device. It is possible for a device
tree to hold unique data — network MAC addresses, for example — but
that is not guaranteed, and some developers think that entropy would
be better served by just feeding the unique data directly.
- New hardware support includes:
- Systems and processors:
Freescale P1023 RDB and C293PCIE boards.
- Graphics:
Qualcomm MSM/Snapdragon GPUs.
The nouveau graphics driver has also gained proper power
management support, and the power management support for Radeon
devices has been improved and extended to a wider range of chips.
- Miscellaneous:
GPIO-controlled backlights,
Sanyo LV5207LP backlight controllers,
Rohm BD6107 backlight controllers,
IdeaPad laptop slidebars,
Toumaz Xenif TZ1090 GPIO controllers,
Kontron ETX/COMexpress GPIO controllers,
Fintek F71882FG and F71889F GPIO controllers,
Dialog Semiconductor DA9063 PMICs,
Samsung S2MPS11 crystal oscillator clocks,
Hisilicon K3 DMA controllers,
Renesas R-Car HPB DMA controllers, and
TI BQ24190 and TWL4030 battery charger controllers.
- Networking:
MOXA ART (RTL8201CP) Ethernet interfaces,
Solarflare SFC9100 interfaces, and
CoreChip-sz SR9700-based Ethernet devices.
- Video4Linux:
Renesas VSP1 video processing engines,
Renesas R-Car video input devices,
Mirics MSi3101 software-defined radio dongles (the first SDR
device supported by the mainline kernel),
Syntek STK1135 USB cameras,
Analog Devices ADV7842 video decoders, and
Analog Devices ADV7511 video encoders.
Changes visible to kernel developers include:
- The GEM and TTM memory managers within the graphics subsystem are now
using a unified subsystem for the management of virtual memory areas,
eliminating some duplicated functionality.
- The new lockref mechanism can now mark
a reference-counted item as being "dead." The separate state is
needed because lockrefs can be used in places (like the dentry cache)
where an item can have a reference count of zero and still be alive
and usable. Once the structure has been marked as dead, though, the
reference count cannot be incremented and the structure cannot be used.
The closing of the merge window still looks to happen on September 15, or,
perhaps, one day later to allow Linus to get back up to speed after his
planned weekend diving experience.
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