3.7 Merge window part 1
A mere 72 days after the beginning of the 3.6 development cycle, the
process has started again with the opening of the 3.7 merge window. As of
this writing, some 5540 non-merge changesets have been pulled into the
mainline, with more to come. Some of the more interesting user-visible
changes merged thus far include:
- The arm64 patch set, adding support
for ARM's 64-bit "AARCH64" architecture, has been merged.
- The perf kvm tool has gained a "stat" command for
analysis of event data. Extensive bash completion support for perf
(for both commands and event names) has also been added.
- The new perf trace tool is meant to function like the
strace utility, but with the ability to show events beyond
system calls. This tool appears to be just getting started; the
message reads "It gets stuck sometimes, but hey, it works
- Applications on the s/390 architecture can now make use of the
System zEC12 hardware transactional memory feature.
- Support for the Intel supervisor mode
access prevention feature has been added.
- The CIFS filesystem now has complete SMB2.1 support; SMB2 is still
marked as experimental, but that's a step forward from its previous
- The ARM subtree cleanup continues; the Tegra subarchitecture is now
fully converted to the device tree mechanism. The unloved and unused
Philips Nexperia PNX4008 subarchitecture support has been removed.
- Extended attributes are now implemented on the control directories for
control groups. This is a Systemd-inspired feature allowing ancillary
information to be attached to control groups.
non-hierarchical control group controllers are used with nested
control groups, a warning will now be emitted. The behavior of those
controllers in that situation might change in the future; see this article for more information.
- The Generic
Routing Encapsulation (GRE) tunneling protocol is now supported
over IPv6. Network address translation (NAT) is also now available
- Server-side support for the TCP fast
open protocol enhancement has been merged.
- The kernel now has support for the VXLAN
tunneling protocol. See Documentation/networking/vxlan.txt for
- The IMA integrity appraisal security
extension has been merged.
- Subject to a configuration option, the "Yama" security module can be
automatically stacked regardless of
which security module is the "primary" module.
- A number of changes improving support for trusted platform module
(TPM) devices have gone in. There is now support for TPM modules
supporting the TCG TIS 1.2 specification and Infineon's I2C 0.20
specification. IBM virtual TPMs are now supported. The "physical
presence interface" mechanism is also supported, making TPM
- New hardware support includes:
- Boards and processors:
Broadcom BCM2835 SoCs,
Raspberry Pi boards, and
Micrel KS8695 SoC-based boards.
s/390 "storage class memory" devices,
Calxeda Highbank SATA controllers, and
QLogic ISP83xx iSCSI host adapters.
Sony PS3 BD remote controls.
Fairchild FAN53555 regulators,
Maxim 8907 voltage regulators,
Freescale i.MX28 LRADC analog to digital converters (ADCs),
Analog Devices AD7787, AD7788, AD7789, AD7790 and AD7791 SPI ADCs,
Analog Devices AD5755/AD5755-1/AD5757/AD5735/AD5737 ADCs,
TI LP8788 ADCs,
Maxim MAX197 ADCs,
Analog Devices ADT7410 temperature monitoring chips,
Samsung GPIO/pinmux controllers,
Nomadik DB8540 pin controllers,
Freescale IMX35 pin controllers,
Avionic Design N-bit GPIO expanders,
Broadcom BCM2835 GPIO units,
Freescale MXS SPI controllers, and
NXP SC18IS602/603 SPI controllers.
Silicom Bypass network interface cards,
Freescale XGMAC MDIO controllers, and
Microchip MRF24J40 transceivers.
NXP SCCNXP serial ports,
NXP LPC32XX high speed serial ports,
Maxim MAX3108 UARTs, and
Digi Realport remote serial devices.
Broadcom BCM63xx peripheral controllers,
Marvell USB 3.0 PHY controllers,
ZTE USB to serial devices, and
Cambridge Electronic Design 1401 USB devices (described as
"whatever that is" in the Kconfig entry).
Changes visible to kernel developers include:
- The regulator subsystem now supports a "bypass mode" wherein the
input is connected directly to the output.
- The handling of read-copy-update grace periods has been pushed into a
set of kernel threads, allowing for better preemptability and reduced
power consumption; The October 11 LWN Weekly Edition will
include an article on this work. RCU has also seen work to allow
user-mode execution to be seen as a sort of quiescent state; this is a
necessary precondition to fully tickless execution.
- There is a new "parking" facility for kernel threads. The primary
purpose is to provide a lightweight mechanism to get these threads out
of the way when CPU hotplug events are processed.
- The new TIMER_IRQSAFE timer flag causes the timer function to
be executed with interrupts off. It exists to make it possible to
safely wait for (and cancel) timers from within interrupt handlers.
- There is a new sensor framework for human input devices; it registers
a multifunction device for each sensor hub and enumerates the sensors
found attached to it. See Documentation/hid/hid-sensor.txt for
- The firmware caching API has been
merged. This subsystem will pull copies of potentially interesting
device firmware into memory just prior to a system suspend, thus
ensuring that the firmware will be available at resume time.
- The feature-removal.txt file is now a removed feature. Linus
it, saying: "There is never any reason to add stuff to this
idiotic file. Either something isn't getting used, and you should
just remove it, or there is no excuse for removing it in the first
place. Just stop the idiocy."
- Initial multiplatform support for the ARM architecture has been
merged. This is an important step toward the "single zImage" goal,
where one kernel can run on a wide variety of ARM systems, but there
is still a lot of work to be done before that goal can be reached.
- The non-reentrant workqueues patch has
been merged. There are also new mod_delayed_work() and
mod_delayed_work_on() functions to modify the expiration time
for delayed work items.
- The user namespace conversion work
continues, meaning that the newish kuid_t and kgid_t
types are appearing in more kernel subsystems.
The 3.7 merge window can be expected to stay open until approximately
October 14. That said, Linus has warned the community that he will be
traveling during this time; he, along with your editor, will be at the
Linux Foundation's Korea
Linux Forum. If the travel interferes with the merging process — which
hasn't been a problem in previous merge windows — this merge window may be
extended to compensate.
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