More reliable (in a concurrent environment) shared lock release and broadcasting.

Author: dyemanov

src/jrd/Relation.cpp

@@ -191,7 +191,7 @@ int RelationPermanent::partners_ast_relation(void* ast_object)
 
 		AsyncContextHolder tdbb(dbb, FB_FUNCTION);
 
-		auto oldFlags = relation->rel_flags.fetch_or(REL_check_partners);
+		const auto oldFlags = relation->rel_flags.fetch_or(REL_check_partners);
 		if (!(oldFlags & REL_check_partners))
 			LCK_release(tdbb, lock);
 	}
@@ -248,10 +248,15 @@ Record* RelationPermanent::getGCRecord(thread_db* tdbb, const Format* const form
 
 void RelationPermanent::checkPartners(thread_db* tdbb)
 {
-	rel_flags |= REL_check_partners;
+	const auto oldFlags = rel_flags.fetch_or(REL_check_partners);
+	if (!(oldFlags & REL_check_partners))
+		LCK_release(tdbb, rel_partners_lock);
+
+	Lock tempLock(tdbb, 0, LCK_rel_partners);
+	tempLock.setKey(rel_id);
 
-	LCK_lock(tdbb, rel_partners_lock, LCK_EX, LCK_WAIT);
-	LCK_release(tdbb, rel_partners_lock);
+	if (LCK_lock(tdbb, &tempLock, LCK_EX, LCK_WAIT))
+		LCK_release(tdbb, &tempLock);
 }
 
 bool RelationPermanent::isReplicating(thread_db* tdbb)