Create a multiplexing structure for signals to Postgres child processes.

This patch gets us out from under the Unix limitation of two user-defined
signal types.  We already had done something similar for signals directed to
the postmaster process; this adds multiplexing for signals directed to
backends and auxiliary processes (so long as they're connected to shared
memory).

As proof of concept, replace the former usage of SIGUSR1 and SIGUSR2
for backends with use of the multiplexing mechanism.  There are still some
hard-wired definitions of SIGUSR1 and SIGUSR2 for other process types,
but getting rid of those doesn't seem interesting at the moment.

Fujii Masao

1 files changed, 9 insertions, 6 deletions

diff --git a/src/backend/storage/ipc/sinvaladt.c b/src/backend/storage/ipc/sinvaladt.c
index fcd1e42a7f6..dfa0ad7b5eb 100644
--- a/src/backend/storage/ipc/sinvaladt.c
+++ b/src/backend/storage/ipc/sinvaladt.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.78 2009/06/11 14:49:02 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.79 2009/07/31 20:26:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 #include "storage/backendid.h"
 #include "storage/ipc.h"
 #include "storage/proc.h"
+#include "storage/procsignal.h"
 #include "storage/shmem.h"
 #include "storage/sinvaladt.h"
 #include "storage/spin.h"
@@ -118,7 +119,7 @@
  * we exceed CLEANUP_MIN.  Should be a power of 2 for speed.
  *
  * SIG_THRESHOLD: the minimum number of messages a backend must have fallen
- * behind before we'll send it SIGUSR1.
+ * behind before we'll send it PROCSIG_CATCHUP_INTERRUPT.
  *
  * WRITE_QUANTUM: the max number of messages to push into the buffer per
  * iteration of SIInsertDataEntries.  Noncritical but should be less than
@@ -551,7 +552,7 @@ SIGetDataEntries(SharedInvalidationMessage *data, int datasize)
  * minFree is the minimum number of message slots to make free.
  *
  * Possible side effects of this routine include marking one or more
- * backends as "reset" in the array, and sending a catchup interrupt (SIGUSR1)
+ * backends as "reset" in the array, and sending PROCSIG_CATCHUP_INTERRUPT
  * to some backend that seems to be getting too far behind.  We signal at
  * most one backend at a time, for reasons explained at the top of the file.
  *
@@ -644,18 +645,20 @@ SICleanupQueue(bool callerHasWriteLock, int minFree)
 		segP->nextThreshold = (numMsgs / CLEANUP_QUANTUM + 1) * CLEANUP_QUANTUM;
 
 	/*
-	 * Lastly, signal anyone who needs a catchup interrupt.  Since kill()
-	 * might not be fast, we don't want to hold locks while executing it.
+	 * Lastly, signal anyone who needs a catchup interrupt.  Since
+	 * SendProcSignal() might not be fast, we don't want to hold locks while
+	 * executing it.
 	 */
 	if (needSig)
 	{
 		pid_t		his_pid = needSig->procPid;
+		BackendId	his_backendId = (needSig - &segP->procState[0]) + 1;
 
 		needSig->signaled = true;
 		LWLockRelease(SInvalReadLock);
 		LWLockRelease(SInvalWriteLock);
 		elog(DEBUG4, "sending sinval catchup signal to PID %d", (int) his_pid);
-		kill(his_pid, SIGUSR1);
+		SendProcSignal(his_pid, PROCSIG_CATCHUP_INTERRUPT, his_backendId);
 		if (callerHasWriteLock)
 			LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
 	}