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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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10
src/backend/postmaster/walwriter.c
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@@ -252,7 +252,7 @@ WalWriterMain(void)
}
/* Clear any already-pending wakeups */
ResetLatch(&MyProc->procLatch);
ResetLatch(MyLatch);
/*
* Process any requests or signals received recently.
@@ -287,7 +287,7 @@ WalWriterMain(void)
else
cur_timeout = WalWriterDelay * HIBERNATE_FACTOR;
rc = WaitLatch(&MyProc->procLatch,
rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
cur_timeout);
@@ -345,8 +345,7 @@ WalSigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}
@@ -358,8 +357,7 @@ WalShutdownHandler(SIGNAL_ARGS)
int save_errno = errno;
shutdown_requested = true;
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}