Use "(void)" to mark pgstat_lock_entry(..., false) calls.

This should silence Coverity's complaints about the result being
sometimes ignored.

I'm inclined to think that these routines are simply misdesigned,
because sometimes it's okay to ignore the result and sometimes it
isn't, and we have no way to enforce the latter.  But for now
I just added a comment.

3 files changed, 12 insertions, 3 deletions

diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 0005021f644..21bdff106a9 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -1019,7 +1019,7 @@ pgstat_fetch_entry(PgStat_Kind kind, Oid dboid, uint64 objid)
 		stats_data = MemoryContextAlloc(pgStatLocal.snapshot.context,
 										kind_info->shared_data_len);
 
-	pgstat_lock_entry_shared(entry_ref, false);
+	(void) pgstat_lock_entry_shared(entry_ref, false);
 	memcpy(stats_data,
 		   pgstat_get_entry_data(kind, entry_ref->shared_stats),
 		   kind_info->shared_data_len);
diff --git a/src/backend/utils/activity/pgstat_database.c b/src/backend/utils/activity/pgstat_database.c
index fbaf8364117..52d82d25352 100644
--- a/src/backend/utils/activity/pgstat_database.c
+++ b/src/backend/utils/activity/pgstat_database.c
@@ -195,7 +195,7 @@ pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount)
 		return;
 	}
 
-	pgstat_lock_entry(entry_ref, false);
+	(void) pgstat_lock_entry(entry_ref, false);
 
 	sharedent = (PgStatShared_Database *) entry_ref->shared_stats;
 	sharedent->stats.checksum_failures += failurecount;
diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c
index 5cd24303755..2e33293b000 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -643,6 +643,13 @@ pgstat_release_entry_ref(PgStat_HashKey key, PgStat_EntryRef *entry_ref,
 		pfree(entry_ref);
 }
 
+/*
+ * Acquire exclusive lock on the entry.
+ *
+ * If nowait is true, it's just a conditional acquire, and the result
+ * *must* be checked to verify success.
+ * If nowait is false, waits as necessary, always returning true.
+ */
 bool
 pgstat_lock_entry(PgStat_EntryRef *entry_ref, bool nowait)
 {
@@ -656,8 +663,10 @@ pgstat_lock_entry(PgStat_EntryRef *entry_ref, bool nowait)
 }
 
 /*
+ * Acquire shared lock on the entry.
+ *
  * Separate from pgstat_lock_entry() as most callers will need to lock
- * exclusively.
+ * exclusively.  The wait semantics are identical.
  */
 bool
 pgstat_lock_entry_shared(PgStat_EntryRef *entry_ref, bool nowait)