vgsp-sema r561: bound the pin-injection drain per service pass (starved ring walk)

r559 soak2 evidence (victory_saxpy, 167 s at 100% CPU, module alive and
printing stats but consuming no GPFIFO entries): the guest pin stream
flooded the injection queue (svc_handle_map_add: 1867-6101 callbacks
suppressed per burst, several bursts per 10 s) and the unbounded for(;;)
drain spent every service pass processing injections, so the ring walk
never ran - work_guard counters froze (deferred=513 applied=50 unchanged
for minutes) and the client spun.

Process at most 64 queued requests per svc_handle_map_add() call. The
drain runs again on every service pass and from svc_gr_request/
svc_run_ops, so nothing is lost; under a flood the ring walk now gets its
cycles every pass. Bounded batches are the same fairness rule the ring
walk itself already uses.

0 files changed, 0 insertions, 0 deletions