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Fix locks in TextureLoader class #1147

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Fix locks in TextureLoader class #1147

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8a0ae72
Fix locks in TextureLoader class
xezon Aug 21, 2024
8fbff61
Additional opt
xezon Aug 21, 2024
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81 changes: 62 additions & 19 deletions src/w3d/renderer/textureloader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -81,9 +81,18 @@ w3dtexture_t Load_Compressed_Texture(
void LoaderThreadClass::Thread_Function()
{
while (m_isRunning) {
if (!g_backgroundQueue.Empty()) {
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Lock for g_backgroundQueue is missing here on read.

bool backgroundQueueEmpty;
{
FastCriticalSectionClass::LockClass background_lock(g_backgroundCritSec);
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Originally takes both locks at the same time. This can be risky and introduce ABA deadlock problem. This can be avoided by limiting scope.

Could perhaps deadlock with TextureLoader::Request_Foreground_Loading.

TextureLoadTaskClass *task = g_backgroundQueue.Pop_Front();
backgroundQueueEmpty = g_backgroundQueue.Empty();
}

if (!backgroundQueueEmpty) {
TextureLoadTaskClass *task;
{
FastCriticalSectionClass::LockClass background_lock(g_backgroundCritSec);
task = g_backgroundQueue.Pop_Front();
}
if (task) {
task->Load();
FastCriticalSectionClass::LockClass foreground_lock(g_foregroundCritSec);
Expand Down Expand Up @@ -282,21 +291,24 @@ w3dsurface_t TextureLoader::Load_Surface_Immediate(const StringClass &texture, W
*/
void TextureLoader::Request_Thumbnail(TextureBaseClass *texture)
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
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Lock scope can be limited. Optimization.

if (texture->Peek_Platform_Base_Texture() == W3D_TYPE_INVALID_TEXTURE) {
if (TextureLoader::Is_DX8_Thread()) {
Load_Thumbnail(texture);
// This seems at odds with the Renegade code where the load tasks are the other way around.
// Possibly this code isn't ever actually used with Thumbnail code in general being minimally
// called.
if (texture->Get_Thumbnail_Load_Task() != nullptr) {
g_foregroundQueue.Remove(texture->Get_Thumbnail_Load_Task());
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Remove(texture->Get_Thumbnail_Load_Task());
}
texture->Get_Thumbnail_Load_Task()->Destroy();
}
} else {
if (texture->Get_Thumbnail_Load_Task() == nullptr) {
if (texture->Get_Normal_Load_Task() == nullptr
|| texture->Get_Normal_Load_Task()->Get_Load_State() == TextureLoadTaskClass::STATE_NONE) {
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Push_Back(TextureLoadTaskClass::Create(
texture, TextureLoadTaskClass::TASK_THUMBNAIL, TextureLoadTaskClass::PRIORITY_BACKGROUND));
}
Expand All @@ -312,15 +324,14 @@ void TextureLoader::Request_Thumbnail(TextureBaseClass *texture)
*/
void TextureLoader::Request_Background_Loading(TextureBaseClass *texture)
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
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Lock scope can be limited. Optimization.


if (!texture->Is_Initialized() && texture->Get_Normal_Load_Task() == nullptr) {
TextureLoadTaskClass *task = TextureLoadTaskClass::Create(
texture, TextureLoadTaskClass::TASK_LOAD, TextureLoadTaskClass::PRIORITY_BACKGROUND);

if (TextureLoader::Is_DX8_Thread()) {
TextureLoader::Begin_Load_And_Queue(task);
} else {
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Push_Back(task);
}
}
Expand All @@ -334,7 +345,6 @@ void TextureLoader::Request_Background_Loading(TextureBaseClass *texture)
void TextureLoader::Request_Foreground_Loading(TextureBaseClass *texture)
{
captainslog_assert(texture != nullptr);
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);

if (texture->Is_Initialized()) {
return;
Expand All @@ -344,32 +354,47 @@ void TextureLoader::Request_Foreground_Loading(TextureBaseClass *texture)
TextureLoadTaskClass *thumb_task = texture->Get_Thumbnail_Load_Task();

if (!TextureLoader::Is_DX8_Thread()) {
FastCriticalSectionClass::LockClass lock2(g_backgroundCritSec);
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Originally takes both locks at the same time. This can be risky and introduce ABA deadlock problem. This can be avoided by limiting scope.

Could perhaps deadlock with LoaderThreadClass::Thread_Function

if (thumb_task != nullptr) {
thumb_task->Set_Load_State(TextureLoadTaskClass::STATE_FOREGROUND_OVERRIDE);
}

if (task != nullptr) {
if (task->Get_Parent() == &g_backgroundQueue) {
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This does not need locking. g_backgroundQueue address never changes.

g_backgroundQueue.Remove(task);
g_foregroundQueue.Push_Back(task);
{
FastCriticalSectionClass::LockClass lock(g_backgroundCritSec);
g_backgroundQueue.Remove(task);
}
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Push_Back(task);
}
}

task->Set_Priority(TextureLoadTaskClass::PRIORITY_FOREGROUND);
} else {
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Push_Back(TextureLoadTaskClass::Create(
texture, TextureLoadTaskClass::TASK_LOAD, TextureLoadTaskClass::PRIORITY_FOREGROUND));
}
} else {
if (thumb_task != nullptr) {
g_foregroundQueue.Remove(thumb_task);
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Remove(thumb_task);
}
thumb_task->Destroy();
}

if (task != nullptr) {
FastCriticalSectionClass::LockClass lock2(g_backgroundCritSec);
g_foregroundQueue.Remove(task);
g_backgroundQueue.Remove(task);
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
g_foregroundQueue.Remove(task);
}
{
FastCriticalSectionClass::LockClass lock(g_backgroundCritSec);
g_backgroundQueue.Remove(task);
}
} else {
task = TextureLoadTaskClass::Create(
texture, TextureLoadTaskClass::TASK_LOAD, TextureLoadTaskClass::PRIORITY_FOREGROUND);
Expand All @@ -385,9 +410,17 @@ void TextureLoader::Request_Foreground_Loading(TextureBaseClass *texture)
*/
bool TextureLoader::Queues_Not_Empty()
{
FastCriticalSectionClass::LockClass lock(g_backgroundCritSec);

return !g_backgroundQueue.Empty() && !g_foregroundQueue.Empty();
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Lock for g_foregroundQueue is missing here on read.

bool backgroundQueueEmpty;
bool foregroundQueueEmpty;
{
FastCriticalSectionClass::LockClass lock(g_backgroundCritSec);
backgroundQueueEmpty = g_backgroundQueue.Empty();
}
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
foregroundQueueEmpty = g_foregroundQueue.Empty();
}
return !backgroundQueueEmpty && !foregroundQueueEmpty;
}

bool TextureLoader::Is_Format_Compressed(WW3DFormat format, bool allow_compressed)
Expand Down Expand Up @@ -424,11 +457,19 @@ void TextureLoader::Flush_Pending_Load_Tasks()
void TextureLoader::Update(void (*update)(void))
{
if (!s_textureLoadSuspended) {
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);

int time = rts::Get_Time();
TextureLoadTaskClass *task;

while ((task = g_foregroundQueue.Pop_Front()) != nullptr) {
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Lock exists before already, but scope can be limited. Optimization.

while (true) {
{
FastCriticalSectionClass::LockClass lock(g_foregroundCritSec);
task = g_foregroundQueue.Pop_Front();
}
if (task == nullptr) {
break;
}

if (update != nullptr) {
int time2 = rts::Get_Time();

Expand Down Expand Up @@ -457,7 +498,8 @@ void TextureLoader::Process_Foreground_Thumbnail(TextureLoadTaskClass *task)
switch (task->Get_Load_State()) {
case TextureLoadTaskClass::STATE_NONE:
Load_Thumbnail(task->Get_Texture());
case TextureLoadTaskClass::STATE_FOREGROUND_OVERRIDE: // Fallthrough
[[fallthrough]];
case TextureLoadTaskClass::STATE_FOREGROUND_OVERRIDE:
task->Destroy();
break;
default:
Expand Down Expand Up @@ -503,6 +545,7 @@ void TextureLoader::Begin_Load_And_Queue(TextureLoadTaskClass *task)

// If we can't start the load of either a dds or tga for the filename in the task set it to missing.
if (task->Begin_Load()) {
FastCriticalSectionClass::LockClass lock(g_backgroundCritSec);
g_backgroundQueue.Push_Front(task);
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Lock is missing here on write. Could race.

} else {
task->Apply_Missing_Texture();
Expand Down
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