← PracticeAdvancedFailure

Every Core at 100%, Nothing Completing

Pull up the evidence one item at a time, commit to a diagnosis, and only then see the schedule that actually ran.

What was reported

Inventory reservation. At 12:00 sharp, when the daily drop goes live, all eight cores pin at 100% and completed reservations per second falls to about four. Not zero — four, from a normal three hundred. Nothing is blocked: every thread dump we take shows every thread RUNNABLE. It clears itself after six to ten minutes, which is roughly when the popular item sells out. We have tried more instances; it gets worse.
1reserve(sku, qty):
2    loop:                                  # no bound, no delay
3        row = read(sku)                    # returns { remaining, version }
4        if row.remaining < qty: return SOLD_OUT
5        ok = compare_and_set(sku,
6                 expect_version = row.version,
7                 remaining      = row.remaining - qty)
8        if ok: return RESERVED
9        # lost the race — try again immediately

Evidence

Nothing here is labelled as relevant. Some of it is not.

What is actually happening?