Linux Kernel Selftests
  
  The kernel contains a set of "self tests" under the tools/testing/selftests/
  directory. These are intended to be small unit tests to exercise individual
  code paths in the kernel.

  On some systems, hot-plug tests could hang forever waiting for cpu and
  memory to be ready to be offlined. A special hot-plug target is created
  to run full range of hot-plug tests. In default mode, hot-plug tests run
  in safe mode with a limited scope. In limited mode, cpu-hotplug test is
  run on a single cpu as opposed to all hotplug capable cpus, and memory
  hotplug test is run on 2% of hotplug capable memory instead of 10%.
  
  Running the selftests (hotplug tests are run in limited mode)
  =============================================================

  
  To build the tests:

    $ make -C tools/testing/selftests
  
  
  To run the tests:

    $ make -C tools/testing/selftests run_tests

  To build and run the tests with a single command, use:
    $ make kselftest

  - note that some tests will require root privileges.

  Running a subset of selftests
  ========================================
  You can use the "TARGETS" variable on the make command line to specify
  single test to run, or a list of tests to run.
  
  To run only tests targeted for a single subsystem:
    $  make -C tools/testing/selftests TARGETS=ptrace run_tests
  
  You can specify multiple tests to build and run:
    $  make TARGETS="size timers" kselftest
  
  See the top-level tools/testing/selftests/Makefile for the list of all
  possible targets.

  Running the full range hotplug selftests
  ========================================

  To build the hotplug tests:

    $ make -C tools/testing/selftests hotplug

  To run the hotplug tests:

    $ make -C tools/testing/selftests run_hotplug
  
  - note that some tests will require root privileges.

  Contributing new tests
  ======================
  
  In general, the rules for for selftests are
  
   * Do as much as you can if you're not root;
  
   * Don't take too long;
  
   * Don't break the build on any architecture, and
  
   * Don't cause the top-level "make run_tests" to fail if your feature is
     unconfigured.