Change the autovacuum launcher to use WaitLatch instead of a poll loop.

In pursuit of this (and with the expectation that WaitLatch will be needed
in more places), convert the latch field that was already added to PGPROC
for sync rep into a generic latch that is activated for all PGPROC-owning
processes, and change many of the standard backend signal handlers to set
that latch when a signal happens.  This will allow WaitLatch callers to be
wakened properly by these signals.

In passing, fix a whole bunch of signal handlers that had been hacked to do
things that might change errno, without adding the necessary save/restore
logic for errno.  Also make some minor fixes in unix_latch.c, and clean
up bizarre and unsafe scheme for disowning the process's latch.  Much of
this has to be back-patched into 9.1.

Peter Geoghegan, with additional work by Tom

1 files changed, 15 insertions, 6 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index f035a48e9b4..ed815d137c0 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2643,11 +2643,12 @@ die(SIGNAL_ARGS)
 			InterruptHoldoffCount--;
 			ProcessInterrupts();
 		}
-
-		/* Interrupt any sync rep wait which is currently in progress. */
-		SetLatch(&(MyProc->waitLatch));
 	}
 
+	/* If we're still here, waken anything waiting on the process latch */
+	if (MyProc)
+		SetLatch(&MyProc->procLatch);
+
 	errno = save_errno;
 }
 
@@ -2684,11 +2685,12 @@ StatementCancelHandler(SIGNAL_ARGS)
 			InterruptHoldoffCount--;
 			ProcessInterrupts();
 		}
-
-		/* Interrupt any sync rep wait which is currently in progress. */
-		SetLatch(&(MyProc->waitLatch));
 	}
 
+	/* If we're still here, waken anything waiting on the process latch */
+	if (MyProc)
+		SetLatch(&MyProc->procLatch);
+
 	errno = save_errno;
 }
 
@@ -2696,6 +2698,7 @@ StatementCancelHandler(SIGNAL_ARGS)
 void
 FloatExceptionHandler(SIGNAL_ARGS)
 {
+	/* We're not returning, so no need to save errno */
 	ereport(ERROR,
 			(errcode(ERRCODE_FLOATING_POINT_EXCEPTION),
 			 errmsg("floating-point exception"),
@@ -2708,7 +2711,13 @@ FloatExceptionHandler(SIGNAL_ARGS)
 static void
 SigHupHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	got_SIGHUP = true;
+	if (MyProc)
+		SetLatch(&MyProc->procLatch);
+
+	errno = save_errno;
 }
 
 /*