3.18 Merge window part 2

As of this writing, Linus has pulled 8,722 non-merge changesets into the mainline repository for the 3.18 merge window. At this point, one might reasonably conclude that the merge window is approaching completion, even though Linus had originally talked about keeping it open until around October 26. Your editor would hazard a guess that this merge window will close rather sooner than that.

Some 5,786 changes have been merged since last week's summary. The more interesting user-visible changes include:

• The bpf() system call is now in the mainline. The hooks to use this code (in tracing and packet filtering, for example) will take a little longer, but the core support for a "universal virtual machine" in the kernel is now present.

• The networking performance improvements described in this article have been merged. Among other things, they allow a relatively small system to drive a high-speed interface at full wire speed, even when small packets are being transmitted. Small-packet performance has been a problem area for Linux, so this is an important improvement.

• The Foo-over-UDP subsystem has been merged; it provides support for tunneling protocols via UDP.

• The Data Center TCP (DCTCP) congestion control algorithm is now supported. See the commit message for a lot of information and this page for even more.

• The Generic Network Virtualization Encapsulation (Geneve) protocol is now supported; see this page for more information.

• The fanotify_init() system call has, as the result of a bug, always ignored the O_CLOEXEC option (which requests that the resulting file descriptor be closed should the program call exec()). As of 3.18, that bug has been fixed. There have been some concerns that applications might silently depend on this option not being honored; developers working with the fanotify interface will thus want to pay attention to this change.

• The prctl() system call supports a new PR_SET_MM_MAP operation to set the core parameters of a process's address space layout: where the code and data areas are, the break pointer, where the stack is, etc. See the commit changelog for details on how this interface works.

• The new Xen "pvSCSI" subsystem allows Xen guests to drive SCSI devices that have been assigned to them.

• The SPARC64 architecture now uses four-level page tables, vastly increasing the amount of memory that can be addressed.

• The Smack mandatory access control subsystem has a new "bring-up" mode that can be used to record the permissions a process needs to execute. It is intended to be used in the writing of Smack rules, then compiled out on production systems.

• As usual, the list of features added to the perf events subsystem and the user-space perf tool is long; see this commit message for details.

• New hardware support includes:
  • Systems and processors: Hisilicon HiP04 Cortex A15 systems-on-chip (SoCs), Amlogic Meson6 (8726MX) SoCs, Renesas R-Car E2 (R8A77940) SoCs, Broadcom BCM63xx DSL SoCs, Atmel SAMA5D4 SoCs, and Cavium Inc. Thunder SoCs.

  • Audio: Cirrus Logic CS35L32 codecs, Freescale generic sound cards, Everest ES8328 audio codecs, Freescale ES8328 audio codecs, and Analog Devices SSM4567 audio amplifiers.

  • Miscellaneous: Atmel multi-port DDR SDRAM controllers, Altera SDRAM memory controllers, TI Keystone Navigator controllers, TI Keystone PCIe controllers, Allwinner A31 real-time clocks, Texas Instruments Keystone 2 IRQ controllers, APM X-Gene GPIO and PCIe controllers, Xilinx AXI PCIe host bridges, MEN 14F021P00 board management controllers, IBM coherent accelerators, Rockchip RK808 real-time clocks, and Maxim 77802 real-time clocks.

  • Networking: Bosch M_CAN controllers, Broadcom UniMAC MDIO bus controllers, Broadcom Starfighter 2 Ethernet switches, Intel FM10000 Ethernet switch host interfaces, Marvell 88E6171 Ethernet switches, and Qualcomm Atheros QCA7000 Ethernet controllers.

  • Video4Linux: CIMaX SP2/SP2HF common interface modules, TechnoTrend TVStick CT2-4650 CI devices, HackRF software-defined radios, DVBSky USB receivers, Hisilicon hix5hd2 IR remote controls, MaxLinear MxL301RF tuners, Sharp QM1D1C0042 tuners, Toshiba TC90522 demodulators, and Earthsoft PT3 PCIe cards.

Changes visible to kernel developers include:

• The longstanding "vivi" test driver in the Video4Linux subsystem has been replaced with a new driver called "vivid." This driver can be used both as an example for how V4L drivers should be written and a module for testing user-space programs.

• The RCU tasks subsystem has been merged; it allows RCU-like behavior under a relaxed set of rules. See this article for details.

• The device tree "resolver" is now available in the kernel. The resolver acts like a sort of linker, resolving references to device tree sections ("phandles") at load time. This work is part of a larger effort to implement run-time configurable device trees.

Stay tuned; next week will include a summary of the changes merged since this article was written.

Index entries for this article
Kernel	Releases/3.18

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