Add barriers to the latch code

Enterprise / PostgreSQL - Andres Freund [anarazel.de] - 13 January 2015 05:58 UTC

Since their introduction latches have required barriers in SetLatch and ResetLatch - but when they were introduced there wasn't any barrier abstraction. Instead latches were documented to rely on the callsites to provide barrier semantics.

Now that the barrier support looks halfway complete, add the necessary barriers to both latch implementations.

Also remove a now superflous lock acquisition from syncrep.c and a superflous (and insufficient) barrier from freelist.c. There might be other cases that can now be simplified, but those are the only ones I've seen on a quick scan.

We might want to backpatch this at some later point, but right now the barrier infrastructure in the backbranches isn't totally on par with master.

Discussion: 20150112154026.GB2092@awork2.anarazel.de

14e8803 Add barriers to the latch code.
src/backend/port/unix_latch.c | 16 +++++++---------
src/backend/port/win32_latch.c | 16 ++++++++++++++++
src/backend/replication/syncrep.c | 10 ----------
src/backend/storage/buffer/freelist.c | 1 -
src/include/storage/latch.h | 7 -------
5 files changed, 23 insertions(+), 27 deletions(-)

Upstream: git.postgresql.org

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