3.4 Merge window part 2

By Jonathan Corbet
March 28, 2012

In the 3.3 release announcement, Linus warned developers that he would be taking a bit of time off during the merge window; that did indeed happen over the last week. Still, he managed to pull some 4,000 changesets since last week's summary. Some of the more significant changes merged in the last week include:

The PowerPC has gained a new firmware-assisted dump facility for the quick capture and analysis of crash dumps.
The GFS2 filesystem now supports the FITRIM ioctl() command which can be used to send discard requests to the underlying storage device.
The prctl() system call has a new option called PR_SET_CHILD_SUBREAPER. Marking a process this way will cause any orphan descendant processes to be reparented to the marked process rather than to the init process. There is a corresponding PR_GET_CHILD_SUBREAPER option as well.
The Microblaze architecture now has high memory support.
The ext4 "noacl" and "noattr" mount options have been marked deprecated with an eye toward removal in the near future. Without these options, it will not be possible to disable ACL and extended attribute support. No other filesystem allows that support to be disabled. The "journal=update" and "resize" mount options have been removed entirely. On the other hand, plans to remove the "bsd_df", "minix_df", "grpid" and "nogrpid" options have been dropped in response to complaints from users.
New hardware support includes:
- Processors and systems: GE Intelligent Platforms IMP3A boards, Atmel AT91SAM9x5 processors, Bluegiga APX4 development kits, and OMAP4 "remote" processors (see below).
- Audio: Wolfson WM2200 CODECs, and Maxim MAX9768 amplifiers.
- Graphics: Intel Medfield-based GMA500 adapters, NVIDIA Kepler chipsets (mode-setting only), ATI RadeonHD 7xxx and "Trinity" chipsets, USB-attached Displaylink video adapters, Samsung S5PC210 and EXYNOS MIPI-DSI controllers, and Intel 750 graphics cards.
- Input: Cypress TrueTouch Standard Product touchscreen controllers, Synaptics USB touchpads, TI touchscreen controllers, MAXIM MAX8997 haptic controllers, and Ilitek ILI210X based touchscreens.
- Miscellaneous: Freescale IFC external NAND controllers, NVIDIA Tegra pinmuxes, CSR SiRFprimaII-based I2C interfaces, TI LP8550/LP8551/LP8552/LP8553/LP8556 backlight devices, Pandora console backlight devices, and Dialog DA9052/DA9053 RTCs.
  Video4Linux: Afatech AF9005 based DVB-T/DVB-C receivers, and Keene FM transmitters.

Changes visible to kernel developers include:

A new subsystem called "remoteproc" has been merged; it allows for the control of remote processors (those on the same SoC but running something other than Linux) through shared memory. The new "rpmsg" subsystem is a virtio-based mechanism for communicating with those processors. There will probably be a separate article on these facilities soon; in the meantime, see Documentation/remoteproc.txt and rpmsg.txt for more information.
The new for_each_clear_bit() macro iterates through each un-set bit in a word.
The poll_requested_events() function has been added as a way for drivers to learn exactly what events user space is polling for. Also added is:
```
    bool poll_does_not_wait(const poll_table *p);
```
which returns true iff it is known that the poll() call will not block.

Also worthy of note is that there has been a vast amount of work done in the ARM architecture tree; the process of consolidating and cleaning up the ARM code continues at a high rate.

The 3.4 merge window would normally be expected to end around April 2. When he announced his vacation, Linus said that he would extend the merge window for a bit if necessary - though he warned that he would still only consider pull requests received during the window. Whether that will happen remains to be seen; either way, next week's Kernel Page will summarize the last new features merged for 3.4.

Index entries for this article
Kernel	Releases/3.4

3.4 Merge window part 2

Posted Mar 29, 2012 19:25 UTC (Thu) by kjp (guest, #39639) [Link] (2 responses)

Uhm, I'm not quite getting all the details on the PR_SET_CHILD_SUBREAPER thing. Is that going to break existing code that does:

if (getppid() == 1) /* parent died already? */

3.4 Merge window part 2

Posted Mar 29, 2012 19:28 UTC (Thu) by kjp (guest, #39639) [Link]

By the way, thats for existing user client code we have to detect when the main gui process dies.

prctl(PR_SET_PDEATHSIG, SIGHUP);
if (getppid() == 1) /* parent died already? */
return 0;

3.4 Merge window part 2

Posted Mar 29, 2012 20:26 UTC (Thu) by alecs1 (guest, #46699) [Link]

You'd have to use the option to get into this situation, in my understanding. Remember that Linus is very adverse to breaking existing programs, and this is my main assumption.

3.4 Merge window part 2

Posted Mar 29, 2012 20:22 UTC (Thu) by arnd (subscriber, #8866) [Link] (1 responses)

A few noteworthy things were merged for the ARM architecture just yesterday. I'm not sure if they got left out because they were buried under all the other patches, or because the list was made before they got merged.

These are the top three in my opinion:

* common struct clk: This has been worked on for years and finally got to the point where enough people can start using the version. Work is continuing in tree, but I expect a lot of conversions to this in v3.5, as a big step towards a single multiplatform kernel image. See also http://lwn.net/Articles/486841/

* Support for the Samsung Exynos5 platform, the first one supported upstream that is based on the ARM Cortex-A15

* Support for the Tegra3 chip from NVIDIA

3.4 Merge window part 2

Posted Mar 29, 2012 20:37 UTC (Thu) by corbet (editor, #1) [Link]

There were a number of ARM pulls (wow you have a lot of trees! :) that came in after I stopped looking for the week.