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.