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Fix locks in TextureLoader class #1147

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Fix locks in TextureLoader class #1147

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xezon
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@xezon xezon commented Aug 21, 2024

xezon
xezon commented Aug 21, 2024
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src/w3d/renderer/textureloader.cpp
@@ -503,6 +542,7 @@ 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.

src/w3d/renderer/textureloader.cpp
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.

src/w3d/renderer/textureloader.cpp
@@ -385,9 +408,17 @@ 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.

src/w3d/renderer/textureloader.cpp
@@ -344,32 +352,47 @@ 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

src/w3d/renderer/textureloader.cpp
@@ -344,32 +352,47 @@ 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);
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.

src/w3d/renderer/textureloader.cpp
@@ -312,15 +322,14 @@ 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.

src/w3d/renderer/textureloader.cpp
@@ -282,21 +291,22 @@ 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.

src/w3d/renderer/textureloader.cpp
@@ -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.

src/w3d/renderer/textureloader.cpp
@@ -81,9 +81,18 @@ w3dtexture_t Load_Compressed_Texture(
void LoaderThreadClass::Thread_Function()
{
while (m_isRunning) {
if (!g_backgroundQueue.Empty()) {
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.

@xezon xezon added the fixing label Aug 21, 2024
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w3dview texture crash
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