4.10 Merge window part 1

When Linus Torvalds released the 4.9 kernel on December 11, he repeated his warning that the 4.10 merge window would be shorter than usual to accommodate the holidays. Maintainers were advised to get their pull requests in early, and many have gotten the word. As of this writing, three days into the 4.10 merge window, nearly 6,900 non-merge changesets have been pulled into the mainline repository, a pace that seems likely to continue for a while.

Some of the more interesting user-visible changes merged so far are:

• The writeback throttling patches have been merged; this should help to keep systems more responsive in the face of heavy background writeback activity.

• The arm64 architecture has gained support for user-space probes (uprobes). Also, arm64 can now emulate the "privileged access never" feature, keeping the kernel from accessing user-space memory in unintended ways.

• The networking layer now supports per-UID network packet routing, a feature brought in from the Android world, where it is used to configure per-app routing policies.

• Support for IPv6 segment routing, a source-routing mechanism, has been added to the networking code.

• There is a new BPF map type that implements a least-recently-used (LRU) list. Said new map type does not, unfortunately, come with any new documentation describing how it works. The curious can glean some information from this changelog and the test code.

• It is now possible to attach a BPF program to a control group which then performs network filtering for all processes within that group.

• BPF programs can be attached to the networking lightweight tunnel infrastructure; these programs can make observations about passing traffic or modify that traffic on the fly. The sample code shows how this facility can be used.

• The netfilter subsystem has gained support for "stateful objects", counters and quotas in particular. See this post for some information on this feature.

• On EFI-firmware systems, the kernel can now store some random data as a firmware variable, then use it at boot time to initialize the random-number generator. This allows entropy to be carried over from one boot to the next and should make for stronger randomness immediately after the system boots.

• The perf events subsystem and user-space tooling have seen a lot of changes this time around; see this commit message for a list.

• The "mediated device" mechanism allows software-defined devices to be made available via the VFIO interface. It is intended to facilitate making devices available to virtualized guests. See Documentation/vfio-mediated-device.txt for details.

• The user-space LED driver subsystem has been merged; see Documentation/leds/uleds.txt and this article for more information.

• New hardware support includes:
  • Processors and systems: Intel CPUs with "Turbo Boost Max Technology".

  • Clocks: Mediatek MT2701 clocks, Qualcomm MSM8994 global clock controllers, Qualcomm MSM8994 pin controllers, Qualcomm RPM-based clock controllers, HiSilicon Hi3798CV200 and HI3516CV300 clock controllers, Allwinner A64 clock controllers, and Renesas r8a7743 and r8a7745 clock pulse generators.

  • Graphics: Silicon Image SII8620 HDMI/MHL bridges, TI TFP410 DVI/HDMI bridges, ZTE VOU display controllers, Hisilicon Hibmc GPUs, NXP i.MX23/i.MX28/i.MX6SX MXSFB LCD controllers, and Amlogic Meson display controllers.

  • Industrial I/O: Analog Devices AD7766/AD7767 analog-to-digital controllers (ADCs), ST Microelectronics STM32 ADCs, Texas Instruments LMP91000 potentiostats, Texas Instruments TMP108 temperature sensors, Honeywell ABP pressure sensors, ACCES 104-QUAD-8 quadrature encoders, Domintech ARD10 3-axis accelerometers, MiraMEMS DA311 and DA280 digital accelerometers, STMicroelectronics HTS221 temperature-humidity sensors, and Invensense MPU-3050 gyroscopes.

  • Miscellaneous: ST FDMA DMA engines, Altera Arria10 system resource GPIO controllers, NI PXI NIC78bx LED controllers, Amlogic S905/GX* SD/MMC host controllers, Cadence SD/SDIO/eMMC host controllers, Qualcomm ADSP peripheral image loaders, Synopsis Designware I2S audio interfaces, Analog Devices ADV7511 HDMI Audio interfaces, MediaTek USB3 dual role USB controllers, NXP LPC18XX one-time programmable memory, Broadcom one-time programmable memory controllers, Holtek Ht16K33 LED controllers, Altera SoCFPGA Arria10 FPGA programmers, Fintek F81532/534 USB-to-serial adapters, Marvell Armada 3700 SPI controllers, Freescale i.MX LPSPI controllers, and Microchip TC654/TC655 fan controllers.

  • Networking: Mellanox Technologies SwitchIB and SwitchIB-2 Infiniband switches, Oxford Semiconductor OXNAS dwmac Ethernet controllers, Amlogic Meson GXL Internal PHYs, QorIQ DPAA Ethernet controllers, and Alacritech Slicoss gigabit Ethernet cards.

Changes visible to kernel developers include:

• The new CONFIG_BUG_ON_DATA_CORRUPTION config variable will cause the kernel to oops when data corruption is detected; it is currently applied to the linked-list implementation.

• The low-level mutex implementation has been rewritten to get rid of most of the architecture-specific code.

• The CPU-idle notifier has been deleted after the final user was removed from the kernel.

• All existing CPU hotplug notifiers have been converted to the new state-machine architecture and the notifier mechanism itself is set to be removed by the end of the merge window.

• The configuration mechanism recognizes a new imply keyword. It functions like select except that the named option can still be turned off manually if desired.

• The new vfree_atomic() function frees memory like vfree(); that freeing is deferred to a workqueue, though, so this function can be called in atomic context.

• There is a new mechanism for tracking functional dependencies between otherwise unrelated devices; see the documentation for details.

• The s390 architecture can now make use of the contiguous memory allocator subsystem.

The 4.10 merge window would normally be expected to close on December 25, but it is clear that the merging of patches will stop by the 23rd at the latest. There are a number of important repositories yet to be pulled, so we can expect there to be a fair number of changes merged before that date. As usual, LWN will continue to follow the merge window through the end.

Index entries for this article
Kernel	Releases/4.10

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