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As a result, the incoming task can run past its assigned slice. Fix this by always enabling the scheduler tick for finite-slice EXT tasks and provide a kselftest that reproduces the scenario and verifies that scheduler ticks are delivered correctly. Test is skipped in kernels without available nohz_full CPUS. Test case (using virtme-ng): $ vng -vb --config tools/testing/selftests/sched_ext/config \ --configitem CONFIG_NO_HZ_FULL=y $ vng --append "nohz_full=all" -- \ tools/testing/selftests/sched_ext/runner -t nohz_tick Before: $ vng --append "nohz_full=all" -- tools/testing/selftests/sched_ext/runner -t nohz_tick ===== START ===== TEST: nohz_tick DESCRIPTION: Verify finite EXT slices restart the NOHZ_FULL tick OUTPUT: ERR: nohz_tick.c:270 Finite-slice worker received only 1 scheduler ticks not ok 1 nohz_tick # ===== END ===== ============================= RESULTS: PASSED: 0 SKIPPED: 0 FAILED: 1 Failed tests: - nohz_tick After: $ vng --append "nohz_full=all" -- tools/testing/selftests/sched_ext/runner -t nohz_tick ===== START ===== TEST: nohz_tick DESCRIPTION: Verify finite EXT slices restart the NOHZ_FULL tick OUTPUT: CPU 1 received 4 finite-slice ticks ok 1 nohz_tick # ===== END ===== ============================= RESULTS: PASSED: 1 SKIPPED: 0 FAILED: 0 Andrea Righi (2): sched_ext: Enable tick for finite slices on nohz_full selftests/sched_ext: Verify nohz_full tick behavior kernel/sched/ext/ext.c | 14 +- tools/testing/selftests/sched_ext/Makefile | 1 + tools/testing/selftests/sched_ext/nohz_tick.bpf.c | 65 +++++ tools/testing/selftests/sched_ext/nohz_tick.c | 309 ++++++++++++++++++++++ 4 files changed, 386 insertions(+), 3 deletions(-)