The adversarial review of the branch confirmed the big one: the shm/DMA
page-table walks and their pmm/heap calls ran outside the big kernel lock —
pre-existing, but fatal once the per-space cursors invited sibling threads to
race them (two concurrent creates could orphan a page table: one thread's
region silently unmapped, the frame leaked — a plausible root for the
long-standing intermittent AP ring-3 fault at the shm base). All three paths
now follow the mmap discipline: allocation, object build, record, and handle
under one lock hold with full rollback; the map itself per-page under brief
holds; dma_free's translate/unmap/free per-page likewise.
Contract edges from the same review: thread_spawn into a dying group returns
-ESRCH (was generic -1); process_kill during the condemned window answers
from the latch's stashed supervisor (0 or -EPERM, was -ESRCH once the leader
slot was reaped); exit derives the group reason from its own argument rather
than the racy exit_code global; a worker's thread_exit no longer overwrites a
concurrent group-kill stamp; checkGroupDead now asserts exactly-one
notification via the drained ring. Full suite: 100/100.
Daniel Samson
c8191570e1