Add a default local latch for use in signal handlers.

To do so, move InitializeLatchSupport() into the new common process
initialization functions, and add a new global variable MyLatch.

MyLatch is usable as soon InitPostmasterChild() has been called
(i.e. very early during startup). Initially it points to a process
local latch that exists in all processes. InitProcess/InitAuxiliaryProcess
then replaces that local latch with PGPROC->procLatch. During shutdown
the reverse happens.

This is primarily advantageous for two reasons: For one it simplifies
dealing with the shared process latch, especially in signal handlers,
because instead of having to check for MyProc, MyLatch can be used
unconditionally. For another, a later patch that makes FEs/BE
communication use latches, now can rely on the existence of a latch,
even before having gone through InitProcess.

Discussion: 20140927191243.GD5423@alap3.anarazel.de

1 files changed, 2 insertions, 2 deletions

diff --git a/src/test/modules/test_shm_mq/setup.c b/src/test/modules/test_shm_mq/setup.c
index b049cff2d0..195099095d 100644
--- a/src/test/modules/test_shm_mq/setup.c
+++ b/src/test/modules/test_shm_mq/setup.c
@@ -285,13 +285,13 @@ wait_for_workers_to_become_ready(worker_state *wstate,
 			}
 
 			/* Wait to be signalled. */
-			WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+			WaitLatch(MyLatch, WL_LATCH_SET, 0);
 
 			/* An interrupt may have occurred while we were waiting. */
 			CHECK_FOR_INTERRUPTS();
 
 			/* Reset the latch so we don't spin. */
-			ResetLatch(&MyProc->procLatch);
+			ResetLatch(MyLatch);
 		}
 	}
 	PG_CATCH();