From 0b78cfcc532ed4353019d361fc595012cdf2e7c4 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Fri, 15 Mar 2019 01:02:13 -0400
Subject: [PATCH] kernel/thread: Maintain priority ordering of added mutex
 waiting threads

The kernel keeps the internal waiting list ordered by priority. This is
trivial to do with std::find_if followed by an insertion.
---
 src/core/hle/kernel/thread.cpp | 36 ++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/src/core/hle/kernel/thread.cpp b/src/core/hle/kernel/thread.cpp
index eb54d66516..7706ca9e53 100644
--- a/src/core/hle/kernel/thread.cpp
+++ b/src/core/hle/kernel/thread.cpp
@@ -7,8 +7,6 @@
 #include <optional>
 #include <vector>
 
-#include <boost/range/algorithm_ext/erase.hpp>
-
 #include "common/assert.h"
 #include "common/common_types.h"
 #include "common/logging/log.h"
@@ -269,8 +267,8 @@ void Thread::AddMutexWaiter(SharedPtr<Thread> thread) {
     if (thread->lock_owner == this) {
         // If the thread is already waiting for this thread to release the mutex, ensure that the
         // waiters list is consistent and return without doing anything.
-        auto itr = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
-        ASSERT(itr != wait_mutex_threads.end());
+        const auto iter = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
+        ASSERT(iter != wait_mutex_threads.end());
         return;
     }
 
@@ -278,11 +276,16 @@ void Thread::AddMutexWaiter(SharedPtr<Thread> thread) {
     ASSERT(thread->lock_owner == nullptr);
 
     // Ensure that the thread is not already in the list of mutex waiters
-    auto itr = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
-    ASSERT(itr == wait_mutex_threads.end());
+    const auto iter = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
+    ASSERT(iter == wait_mutex_threads.end());
 
+    // Keep the list in an ordered fashion
+    const auto insertion_point = std::find_if(
+        wait_mutex_threads.begin(), wait_mutex_threads.end(),
+        [&thread](const auto& entry) { return entry->GetPriority() > thread->GetPriority(); });
+    wait_mutex_threads.insert(insertion_point, thread);
     thread->lock_owner = this;
-    wait_mutex_threads.emplace_back(std::move(thread));
+
     UpdatePriority();
 }
 
@@ -290,10 +293,11 @@ void Thread::RemoveMutexWaiter(SharedPtr<Thread> thread) {
     ASSERT(thread->lock_owner == this);
 
     // Ensure that the thread is in the list of mutex waiters
-    auto itr = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
-    ASSERT(itr != wait_mutex_threads.end());
+    const auto iter = std::find(wait_mutex_threads.begin(), wait_mutex_threads.end(), thread);
+    ASSERT(iter != wait_mutex_threads.end());
+
+    wait_mutex_threads.erase(iter);
 
-    boost::remove_erase(wait_mutex_threads, thread);
     thread->lock_owner = nullptr;
     UpdatePriority();
 }
@@ -310,12 +314,18 @@ void Thread::UpdatePriority() {
         return;
 
     scheduler->SetThreadPriority(this, new_priority);
-
     current_priority = new_priority;
 
+    if (!lock_owner) {
+        return;
+    }
+
+    // Ensure that the thread is within the correct location in the waiting list.
+    lock_owner->RemoveMutexWaiter(this);
+    lock_owner->AddMutexWaiter(this);
+
     // Recursively update the priority of the thread that depends on the priority of this one.
-    if (lock_owner)
-        lock_owner->UpdatePriority();
+    lock_owner->UpdatePriority();
 }
 
 void Thread::ChangeCore(u32 core, u64 mask) {