diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 48478b1024..37fd80388c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2036,7 +2036,7 @@ include_dir 'conf.d'
         and <literal>mmap</literal> (to simulate shared memory using
         memory-mapped files stored in the data directory).
         Not all values are supported on all platforms; the first supported
-        option is the default for that platform.  The use of the
+        option is usually the default for that platform.  The use of the
         <literal>mmap</literal> option, which is not the default on any platform,
         is generally discouraged because the operating system may write
         modified pages back to disk repeatedly, increasing system I/O load;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 48ad80cf2e..b4bc06e5f5 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -147,7 +147,7 @@
 					#   sysv
 					#   windows
 					# (change requires restart)
-#dynamic_shared_memory_type = posix	# the default is the first option
+#dynamic_shared_memory_type = posix	# the default is usually the first option
 					# supported by the operating system:
 					#   posix
 					#   sysv
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index ed6de7ca94..89b888eaa5 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -842,11 +842,14 @@ set_null_conf(void)
  * segment in dsm_impl.c; if it doesn't work, we assume it won't work for
  * the postmaster either, and configure the cluster for System V shared
  * memory instead.
+ *
+ * We avoid choosing Solaris's implementation of shm_open() by default.  It
+ * can sleep and fail spuriously under contention.
  */
 static const char *
 choose_dsm_implementation(void)
 {
-#ifdef HAVE_SHM_OPEN
+#if defined(HAVE_SHM_OPEN) && !defined(__sun__)
 	int			ntries = 10;
 	pg_prng_state prng_state;