Hold required lock when initializing shmem

According to the documentation, each backend is supposed to hold
AddinShmemInitLock when calling ShmemInitStruct. We only did that for
half of our calls before this patch.

Author: AndersAstrand

contrib/pg_tde/src/access/pg_tde_xlog_smgr.c

@@ -158,6 +158,8 @@ TDEXLogShmemInit(void)
 {
 	bool		foundBuf;
 
+	Assert(LWLockHeldByMeInMode(AddinShmemInitLock, LW_EXCLUSIVE));
+
 	EncryptionState = (EncryptionStateData *)
 		ShmemInitStruct("TDE XLog Encryption State",
 						TDEXLogEncryptStateSize(),

contrib/pg_tde/src/catalog/tde_principal_key.c

@@ -127,7 +127,7 @@ PrincipalKeyShmemInit(void)
 	char	   *free_start;
 	Size		required_shmem_size = PrincipalKeyShmemSize();
 
-	LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
+	Assert(LWLockHeldByMeInMode(AddinShmemInitLock, LW_EXCLUSIVE));
 
 	/* Create or attach to the shared memory state */
 	ereport(NOTICE, errmsg("PrincipalKeyShmemInit: requested %ld bytes", required_shmem_size));
@@ -175,8 +175,6 @@ PrincipalKeyShmemInit(void)
 
 		dshash_detach(dsh);
 	}
-
-	LWLockRelease(AddinShmemInitLock);
 }
 
 /*

contrib/pg_tde/src/pg_tde.c

@@ -64,11 +64,15 @@ tde_shmem_startup(void)
 	if (prev_shmem_startup_hook)
 		prev_shmem_startup_hook();
 
+	LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
+
 	KeyProviderShmemInit();
 	PrincipalKeyShmemInit();
 	TDEXLogShmemInit();
 	TDEXLogSmgrInit();
 	TDEXLogSmgrInitWrite(EncryptXLog);
+
+	LWLockRelease(AddinShmemInitLock);
 }
 
 void