From ffe7df793adfaf116f25fd335b777e2a74b61da5 Mon Sep 17 00:00:00 2001
From: Marin Tomic <marin.tomic@memgraph.io>
Date: Mon, 19 Mar 2018 15:15:17 +0100
Subject: [PATCH] Remove writers preference test for RWLock

Summary:
Writers preference is not guaranteed by the standard and as such
 there are variations between implementations in different versions
of libphthread.

Reviewers: dgleich

Reviewed By: dgleich

Differential Revision: https://phabricator.memgraph.io/D1305
---
 src/threading/sync/rwlock.hpp |  3 +--
 tests/unit/rwlock.cpp         | 47 -----------------------------------
 2 files changed, 1 insertion(+), 49 deletions(-)

diff --git a/src/threading/sync/rwlock.hpp b/src/threading/sync/rwlock.hpp
index 88838b353..2752b0b64 100644
--- a/src/threading/sync/rwlock.hpp
+++ b/src/threading/sync/rwlock.hpp
@@ -13,8 +13,7 @@ namespace threading {
 /// though there is a thread waiting for an exclusive (write) lock, which can
 /// lead to writer starvation. If the priority is set to `WRITE`, readers will
 /// be blocked from obtaining new shared locks while there are writers waiting,
-/// which can lead to reader starvation. However, if there is an exclusive lock
-/// held, writers will always be preferred upon it's release.
+/// which can lead to reader starvation.
 enum RWLockPriority { READ, WRITE };
 
 /// A wrapper around `pthread_rwlock_t`, useful because it is not possible to
diff --git a/tests/unit/rwlock.cpp b/tests/unit/rwlock.cpp
index 030ea8a36..6410931d8 100644
--- a/tests/unit/rwlock.cpp
+++ b/tests/unit/rwlock.cpp
@@ -52,53 +52,6 @@ TEST(RWLock, SingleWriter) {
   EXPECT_GE(timer.Elapsed(), 290ms);
 }
 
-/* Next two tests demonstrate that writers are always preferred when an unique
- * lock is released. */
-
-TEST(RWLock, WritersPreferred_1) {
-  RWLock rwlock(RWLockPriority::READ);
-  rwlock.lock();
-  bool first = true;
-
-  std::thread t1([&rwlock, &first] {
-    std::shared_lock<RWLock> lock(rwlock);
-    EXPECT_FALSE(first);
-  });
-
-  std::thread t2([&rwlock, &first] {
-    std::unique_lock<RWLock> lock(rwlock);
-    EXPECT_TRUE(first);
-    first = false;
-  });
-
-  std::this_thread::sleep_for(100ms);
-  rwlock.unlock();
-  t1.join();
-  t2.join();
-}
-
-TEST(RWLock, WritersPreferred_2) {
-  RWLock rwlock(RWLockPriority::WRITE);
-  rwlock.lock();
-  bool first = true;
-
-  std::thread t1([&rwlock, &first] {
-    std::shared_lock<RWLock> lock(rwlock);
-    EXPECT_FALSE(first);
-  });
-
-  std::thread t2([&rwlock, &first] {
-    std::unique_lock<RWLock> lock(rwlock);
-    EXPECT_TRUE(first);
-    first = false;
-  });
-
-  std::this_thread::sleep_for(100ms);
-  rwlock.unlock();
-  t1.join();
-  t2.join();
-}
-
 TEST(RWLock, ReadPriority) {
   /*
    * - Main thread is holding a shared lock until T = 100ms.