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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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12
src/backend/tcop/postgres.c
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@ -2607,8 +2607,7 @@ die(SIGNAL_ARGS)
}
/* If we're still here, waken anything waiting on the process latch */
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}
@ -2649,8 +2648,7 @@ StatementCancelHandler(SIGNAL_ARGS)
}
/* If we're still here, waken anything waiting on the process latch */
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}
@ -2675,8 +2673,7 @@ SigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}
@ -2814,8 +2811,7 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
* waiting on that latch, expecting to get interrupted by query cancels et
* al., would also need to set set_latch_on_sigusr1.
*/
if (MyProc)
SetLatch(&MyProc->procLatch);
SetLatch(MyLatch);
errno = save_errno;
}