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Add a default local latch for use in signal handlers.

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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
This commit is contained in:
Andres Freund
2015-01-14 18:45:22 +01:00
parent 85a2a8903f
commit 59f71a0d0b
23 changed files with 136 additions and 134 deletions
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4
src/backend/postmaster/bgworker.c
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@@ -942,7 +942,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
if (status != BGWH_NOT_YET_STARTED)
break;
rc = WaitLatch(&MyProc->procLatch,
rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH, 0);
if (rc & WL_POSTMASTER_DEATH)
@@ -951,7 +951,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
break;
}
ResetLatch(&MyProc->procLatch);
ResetLatch(MyLatch);
}
}
PG_CATCH();