Significant cleanups in SysV IPC handling (shared mem and semaphores).

IPC key assignment will now work correctly even when multiple postmasters
are using same logical port number (which is possible given -k switch).
There is only one shared-mem segment per postmaster now, not 3.
Rip out broken code for non-TAS case in bufmgr and xlog, substitute a
complete S_LOCK emulation using semaphores in spin.c.  TAS and non-TAS
logic is now exactly the same.
When deadlock is detected, "Deadlock detected" is now the elog(ERROR)
message, rather than a NOTICE that comes out before an unhelpful ERROR.

1 files changed, 10 insertions, 87 deletions

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 3b2eb95d4fc..9fa4ebb3689 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.193 2000/11/27 04:03:20 inoue Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.194 2000/11/28 23:27:55 tgl Exp $
  *
  * NOTES
  *
@@ -118,26 +118,6 @@ char * UnixSocketDir;
 char * Virtual_host;
 
 /*
- * This is a sequence number that indicates how many times we've had to
- * throw away the shared memory and start over because we doubted its
- * integrity.	It starts off at zero and is incremented every time we
- * start over.  We use this to ensure that we use a new IPC shared memory
- * key for the new shared memory segment in case the old segment isn't
- * entirely gone yet.
- *
- * The sequence actually cycles back to 0 after 9, so pathologically there
- * could be an IPC failure if 10 sets of backends are all stuck and won't
- * release IPC resources.
- */
-static short shmem_seq = 0;
-
-/*
- * This is the base IPC shared memory key.  Other keys are generated by
- * adding to this.
- */
-static IpcMemoryKey ipc_key;
-
-/*
  * MaxBackends is the actual limit on the number of backends we will
  * start. The default is established by configure, but it can be
  * readjusted from 1..MAXBACKENDS with the postmaster -N switch. Note
@@ -1292,39 +1272,6 @@ ConnFree(Port *conn)
 	free(conn);
 }
 
-/*
- * get_host_port -- return a pseudo port number (16 bits)
- * derived from the primary IP address of Virtual_host.
- */
-static unsigned short
-get_host_port(void)
-{
-	static unsigned short hostPort = 0;
-
-	if (hostPort == 0)
-	{
-		SockAddr	saddr;
-		struct hostent *hp;
-
-		hp = gethostbyname(Virtual_host);
-		if ((hp == NULL) || (hp->h_addrtype != AF_INET))
-		{
-			char msg[1024];
-			snprintf(msg, sizeof(msg),
-				 "FATAL: get_host_port: gethostbyname(%s) failed\n",
-				 Virtual_host);
-			fputs(msg, stderr);
-			pqdebug("%s", msg);
-			exit(1);
-		}
-		memmove((char *) &(saddr.in.sin_addr),
-			(char *) hp->h_addr,
-			hp->h_length);
-		hostPort = ntohl(saddr.in.sin_addr.s_addr) & 0xFFFF;
-	}
-
-	return hostPort;
-}
 
 /*
  * reset_shared -- reset shared memory and semaphores
@@ -1333,40 +1280,16 @@ static void
 reset_shared(unsigned short port)
 {
 	/*
-	 * A typical ipc_key is 5432001, which is port 5432, sequence
-	 * number 0, and 01 as the index in IPCKeyGetBufferMemoryKey().
-	 * The 32-bit INT_MAX is 2147483 6 47.
-	 *
-	 * The default algorithm for calculating the IPC keys assumes that all
-	 * instances of postmaster on a given host are listening on different
-	 * ports.  In order to work (prevent shared memory collisions) if you
-	 * run multiple PostgreSQL instances on the same port and different IP
-	 * addresses on a host, we change the algorithm if you give postmaster
-	 * the -h option, or set PGHOST, to a value other than the internal
-	 * default.
-	 *
-	 * If Virtual_host is set, then we generate the IPC keys using the
-	 * last two octets of the IP address instead of the port number.
-	 * This algorithm assumes that no one will run multiple PostgreSQL
-	 * instances on one host using two IP addresses that have the same two
-	 * last octets in different class C networks.  If anyone does, it
-	 * would be rare.
-	 *
-	 * So, if you use -h or PGHOST, don't try to run two instances of
-	 * PostgreSQL on the same IP address but different ports.  If you
-	 * don't use them, then you must use different ports (via -p or
-	 * PGPORT).  And, of course, don't try to use both approaches on one
-	 * host.
+	 * Reset assignment of shared mem and semaphore IPC keys.
+	 * Doing this means that in normal cases we'll assign the same keys
+	 * on each "cycle of life", and thereby avoid leaving dead IPC objects
+	 * floating around if the postmaster crashes and is restarted.
 	 */
-
-	if (Virtual_host[0] != '\0')
-		port = get_host_port();
-
-	ipc_key = port * 1000 + shmem_seq * 100;
-	CreateSharedMemoryAndSemaphores(ipc_key, MaxBackends);
-	shmem_seq += 1;
-	if (shmem_seq >= 10)
-		shmem_seq -= 10;
+	IpcInitKeyAssignment(port);
+	/*
+	 * Create or re-create shared memory and semaphores.
+	 */
+	CreateSharedMemoryAndSemaphores(false, MaxBackends);
 }