Linux Kernel - Let's contribute

Slides of the talk I did at LinuxWochen Wien 2014.
This talk will give you a quick introduction to Linux kernel development. During the talk we will explore some options of contribution, including random configurations, stable-testing, RC-testing and actual coding! By the end of the talk we will post a basic patch to the developers as well.

Transcript

1. Let's contribute!
   Levente Kurusa
   Presented by
   Fedora Project Hungary
   
   Licensed under CC-BY-SA
   Linux Kernel
   

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2. Topics
   1. Quick introduction
   2. Random configurations
   3. Kernel testing
   a. Stable kernels
   b. RC kernels
   4. Checkpatch patches
   

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3. Quick introduction
   

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4. Linux powers the world!
   Servers! The cloud! Desktop? Maybe this year?
   Open source contribution is always a big plus
   when it comes to job search!
   Linux is cool!
   Why not?
   Why?
   

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5. 86% say Linux advanced their career
   93% of HR will recruit a Linux pro next year
   75% already received a call this year!
   Interesting projects!
   Greater pay check! (+10% this year)
   Some statistics
   

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6. First steps
   Fetch the Linux kernel source code
   For random configurations: linux-next
   http://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
   For stable testing: linux-stable
   http://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
   For Rcs, simply clone down Linus' tree
   http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
   

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7. Eudyptula Challenge
   http://eudyptula-challenge.org/
   Series of programming tasks
   Hard, but fun!
   

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8. Linux-next
   The current state of the kernel
   Merged together by Stephen Rothwell
   An excellent opportunity to start
   Default configurations are tested
   

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9. Linux-stable
   Collection of important patches to old
   kernel release
   Backports needed!
   Maintained by Greg KH and others
   Documentation/stable_kernel_rules.txt
   

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10. Random
    configurations
    

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11. Randomized configurations of the kernel
    Often have a lot of problems
    GCC warnings
    GCC errors
    kconfig errors/warnings
    They sometimes don't even boot
    Extremely useful!
    What are randconfigs?
    

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12. $ make randconfig
    Completely nonsense config!
    Try to build it:
    $ make -j`nproc`
    Your first randconfig
    

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13. Possible errors
    Undeclared functions
    Kconfig circular dependencies
    Boot failure
    Test in emulator!
    

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14. Kernel
    testing
    

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15. Run the latest kernel
    Quite easy!
    $ make defconfig
    $ make localmodconfig
    $ make -j`nproc`
    # make headers_install
    # make install
    # reboot
    

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16. Actual testing
    If you test linux-stable
    ... and things break: Report it!
    ... if nothing breaks: Break it!
    (repeat)
    If you test linux-next
    ... it's risky to try on your computer
    

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17. Actual testing
    I use my own tiny project.
    LATTE – Linux Automatic Testing Tool for Expert
    (https://github.com/levex/latte)
    Emulators are great.
    Benchmarks are also fun.
    perf
    

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18. perf
    # perf list
    # perf record
    # perf report
    # perf stat -e
    

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19. Sending your
    first patch
    ●
    Also known as: Checkpatch patches
    

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20. Checkpatch?
    scripts/checkpatch.pl
    Checks for common errors in the patch
    ... and files with the --file switch
    Not just coding style, but bugs as well!
    

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21. Getting maintainers
    scripts/get_maintainer.pl
    Gives you a list of maintainers for that
    particular patch or file
    ... or you can manually browse through
    the MAINTAINERS file
    

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22. Creating the patch
    $ git reset --hard HEAD
    [work...]
    $ git diff
    [review work...]
    $ git commit -as
    $ git format-patch -1
    … and then the hardest part
    

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23. Sending it
    9 out of 10 will fail this step
    git send-email
    Thunderbird and such can do it as well, but
    it's hard to configure them properly.
    

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24. People on LKML are grumpy!
    Don't be afraid to ask
    RTFM
    Summary
    

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25. Any questions?
    Licensed under CC-BY-SA
    
    @ilevex
    Contact:
    

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