Use barrier semantics when reading/writing writtenUpto The walreceiver publishes its write position lock-free via writtenUpto. On weakly-ordered architectures (ARM, PowerPC), both sides of this handshake need explicit barriers so that the lock-less reader sees a consistent state.
Use pg_atomic_write_membarrier_u64() at both write sites and pg_atomic_read_membarrier_u64() in GetWalRcvWriteRecPtr(). This matches the barrier semantics that GetWalRcvFlushRecPtr() and other LSN-position functions get implicitly from their spinlock acquire/release, and protects from bugs caused by expectations of similar barrier guarantees from different LSN-position functions. Reported-by: Andres Freund <[email protected]> Discussion: https://postgr.es/m/zqbppucpmkeqecfy4s5kscnru4tbk6khp3ozqz6ad2zijz354k%40w4bdf4z3wqoz Author: Xuneng Zhou <[email protected]> Reviewed-by: Andres Freund <[email protected]> Reviewed-by: Alexander Korotkov <[email protected]> Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/dfb690dd52375517138ce1ee0f20a831d9585778 Modified Files -------------- src/backend/replication/walreceiver.c | 2 +- src/backend/replication/walreceiverfuncs.c | 14 +++++++++++--- 2 files changed, 12 insertions(+), 4 deletions(-)
