pub fn default_post_vm_periodic_fired(result: &VmResult) -> Result<()>Expand description
Default post_vm callback emitted by #[ktstr_test] when the
attribute omits post_vm = .... Asserts that at least one
periodic snapshot produced REAL BPF state during the workload
window WHEN periodic was configured (num_snapshots > 0); when
periodic was disabled (num_snapshots == 0), the helper is a
no-op and returns Ok.
This is the smoke-floor for any periodic-configured test:
“the test produced meaningful data.” Importantly, the floor
reads
SnapshotBridge::periodic_real_count —
NOT VmResult::periodic_fired.
The latter counts every periodic boundary the coordinator
attempted, INCLUDING placeholder rows from rendezvous timeouts;
a scheduler that attaches but produces nothing but placeholders
would pass the periodic_fired >= 1 floor and obscure the
broken-scheduler diagnosis. The real-count floor catches that
case (placeholder-only fills surface as zero) while tolerating
the realistic single-snapshot timeout flake (one real capture
among N is enough to pass the floor).
Tests that need stronger assertions (per-snapshot field reads,
per-phase ratios, etc.) supply their own post_vm = my_checker
instead.
The macro routes this fn pointer into KtstrTestEntry::post_vm
so the runner’s existing dispatch path applies it identically
to an author-supplied callback.