A new function EmitProcSignalBarrier() can be used to emit a global barrier which all backends that participate in the ProcSignal mechanism must absorb, and a new function WaitForProcSignalBarrier() can be used to wait until all relevant backends have in fact absorbed the barrier.
This can be used to coordinate global state changes, such as turning checksums on while the system is running.
There's no real client of this mechanism yet, although two are proposed, but an enum has to have at least one element, so this includes a placeholder type (PROCSIGNAL_BARRIER_PLACEHOLDER) which should be replaced by the first real client of this mechanism to get committed.
Andres Freund and Robert Haas, reviewed by Daniel Gustafsson and, in earlier versions, by Magnus Hagander.
16a4e4aecd Extend the ProcSignal mechanism to support barriers.
doc/src/sgml/monitoring.sgml | 6 +-
src/backend/postmaster/autovacuum.c | 4 +
src/backend/postmaster/checkpointer.c | 7 +
src/backend/postmaster/interrupt.c | 4 +
src/backend/postmaster/pgstat.c | 3 +
src/backend/postmaster/startup.c | 6 +-
src/backend/replication/walreceiver.c | 3 +-
src/backend/storage/buffer/bufmgr.c | 10 ++
src/backend/storage/ipc/procsignal.c | 301 ++++++++++++++++++++++++++++++++--
src/backend/tcop/postgres.c | 3 +
src/backend/utils/init/globals.c | 1 +
src/include/miscadmin.h | 1 +
src/include/pgstat.h | 1 +
src/include/storage/procsignal.h | 14 ++
14 files changed, 350 insertions(+), 14 deletions(-)