scx_lavd: fix an SCX_DSQ_LOCAL_ON runtime error in lavd_enqueue#3642
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scx_lavd: fix an SCX_DSQ_LOCAL_ON runtime error in lavd_enqueue#3642likewhatevs wants to merge 3 commits into
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Add lavd_misplaced_local_on. Against unmodified scx_lavd it fails consistently with: SCX_DSQ_LOCAL[_ON] target CPU N not allowed for <task> scx_exit <- task_can_run_on_remote_rq <- dispatch_to_local_dsq Gated behind the ktstr-tests feature. Signed-off-by: Pat Somaru <patso@likewhatevs.io>
…avd_enqueue When the CPU picked in lavd_enqueue is invalid or not in the task's allowed mask, fall back to the task's current CPU. This takes lavd_misplaced_local_on from a consistent failure to a sporadic one: SCX_DSQ_LOCAL[_ON] target CPU N not allowed for <task> scx_exit <- task_can_run_on_remote_rq <- dispatch_to_local_dsq Signed-off-by: Pat Somaru <patso@likewhatevs.io>
… CPU After the off-mask fallback, lavd_misplaced_local_on still failed sporadically, as a runnable-task stall: runnable task stall (<task> failed to run for N s) Direct-dispatch SCX_DSQ_LOCAL_ON only when the picked CPU is the task's current CPU; otherwise enqueue to the domain DSQ. The test then passes. Signed-off-by: Pat Somaru <patso@likewhatevs.io>
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lavd_misplaced_local_on(a new ktstr test, gated behind thektstr-testsfeature) drives scx_lavd into a runtime error. Against unmodified scx_lavd it
fails consistently:
Two changes to
lavd_enqueue, described by their effect on that test:the task's allowed mask. This takes the test from a consistent failure to a
sporadic one (same error).
SCX_DSQ_LOCAL_ONonly when the picked CPU is the task'scurrent CPU; otherwise enqueue to the domain DSQ. The remaining sporadic
failure surfaced as a runnable-task stall (
runnable task stall (<task> failed to run for N s)); after this the test passes.The test is feature-gated, so a normal scx_lavd build is unaffected — the
harness is pulled in only with
--features ktstr-tests.Test plan
lavd_misplaced_local_onpasses with the fix (cargo ktstr test,--features ktstr-tests).