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Protect savestates while the threaded software renderer is running (#1864) 

* First crack at ensuring the render thread doesn't touch GPU state while it's being serialized

* Get rid of the semaphore wait

* Add some extra fields into GPU3D's serialization

* Oops, TempVertexBuffer is already serialized

* Move vertex serialization into its own method

* Lock the GPU3D state when rendering on the render thread or serializing it

* Revert "Lock the GPU3D state when rendering on the render thread or serializing it"

This reverts commit 2f49a551c1.

* Add comments that describe the synchronization within GPU3D_Soft

- I need to understand it before I can solve my actual problem
- Now I do

* Revert "Revert "Lock the GPU3D state when rendering on the render thread or serializing it""

This reverts commit 1977566a6d.

* Let's try locking the GPU3D state throughout NDS::RunFrame

- Just to see what happens

* Slim down the lock's scope

* Narrow the lock's scope some more

* Remove the lock entirely

* Try protecting the GPU3D state with just a mutex

- I'll clean this up once I know it works

* Remove a duplicate method definition

* Add a missing `noexcept` specifier

* Remove an unused function

* Cut some non-hardware state from `GPU3D`'s savestate

* Assume that the next frame after loading a savestate won't be identical

* Actually, it _is_ worth it

* Don't serialize the clip matrix

- It's recalculated anyway

* Serialize `RenderPolygonRAM` as an array of indexes

* Clean up some comments

- I liked the dialogue style, but oh well

* Try restarting the render thread instead of using the lock

- Let's see what happens

* Put the lock back

* Fix some polygon and vertex indexes being saved incorrectly

- Taking the difference between two pointers results in the number of elements, not the number of bytes

* Remove `SoftRenderer::StateBusy` since it turns out we don't need it

- The real synchronization was the friends we made along the way
This commit is contained in:
Jesse Talavera 2024-01-07 17:39:43 -05:00 committed by GitHub
parent f68f55d002
commit 8143f54956
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 128 additions and 53 deletions
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107
src/GPU3D.cpp
View File

@ -146,6 +146,19 @@ GPU3D::GPU3D(melonDS::NDS& nds, std::unique_ptr<Renderer3D>&& renderer) noexcept
{
}
void Vertex::DoSavestate(Savestate* file) noexcept
{
file->VarArray(Position, sizeof(Position));
file->VarArray(Color, sizeof(Color));
file->VarArray(TexCoords, sizeof(TexCoords));
file->Bool32(&Clipped);
file->VarArray(FinalPosition, sizeof(FinalPosition));
file->VarArray(FinalColor, sizeof(FinalColor));
file->VarArray(HiresPosition, sizeof(HiresPosition));
}
void GPU3D::SetCurrentRenderer(std::unique_ptr<Renderer3D>&& renderer) noexcept
{
CurrentRenderer = std::move(renderer);
@ -297,6 +310,12 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
{
file->Section("GP3D");
SoftRenderer* softRenderer = dynamic_cast<SoftRenderer*>(CurrentRenderer.get());
if (softRenderer && softRenderer->IsThreaded())
{
softRenderer->SetupRenderThread(NDS.GPU);
}
CmdFIFO.DoSavestate(file);
CmdPIPE.DoSavestate(file);
@ -372,33 +391,21 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
file->Var32(&VertexNumInPoly);
file->Var32(&NumConsecutivePolygons);
for (int i = 0; i < 4; i++)
for (Vertex& vtx : TempVertexBuffer)
{
Vertex* vtx = &TempVertexBuffer[i];
file->VarArray(vtx->Position, sizeof(s32)*4);
file->VarArray(vtx->Color, sizeof(s32)*3);
file->VarArray(vtx->TexCoords, sizeof(s16)*2);
file->Bool32(&vtx->Clipped);
file->VarArray(vtx->FinalPosition, sizeof(s32)*2);
file->VarArray(vtx->FinalColor, sizeof(s32)*3);
vtx.DoSavestate(file);
}
if (file->Saving)
{
u32 id;
if (LastStripPolygon) id = (u32)((LastStripPolygon - (&PolygonRAM[0])) / sizeof(Polygon));
else id = -1;
file->Var32(&id);
u32 index = LastStripPolygon ? (u32)(LastStripPolygon - &PolygonRAM[0]) : UINT32_MAX;
file->Var32(&index);
}
else
{
u32 id;
file->Var32(&id);
if (id == 0xFFFFFFFF) LastStripPolygon = NULL;
else LastStripPolygon = &PolygonRAM[id];
u32 index = UINT32_MAX;
file->Var32(&index);
LastStripPolygon = (index == UINT32_MAX) ? nullptr : &PolygonRAM[index];
}
file->Var32(&CurRAMBank);
@ -409,18 +416,9 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
file->Var32(&FlushRequest);
file->Var32(&FlushAttributes);
for (int i = 0; i < 6144*2; i++)
for (Vertex& vtx : VertexRAM)
{
Vertex* vtx = &VertexRAM[i];
file->VarArray(vtx->Position, sizeof(s32)*4);
file->VarArray(vtx->Color, sizeof(s32)*3);
file->VarArray(vtx->TexCoords, sizeof(s16)*2);
file->Bool32(&vtx->Clipped);
file->VarArray(vtx->FinalPosition, sizeof(s32)*2);
file->VarArray(vtx->FinalColor, sizeof(s32)*3);
vtx.DoSavestate(file);
}
for(int i = 0; i < 2048*2; i++)
@ -434,20 +432,17 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
for (int j = 0; j < 10; j++)
{
Vertex* ptr = poly->Vertices[j];
u32 id;
if (ptr) id = (u32)((ptr - (&VertexRAM[0])) / sizeof(Vertex));
else id = -1;
file->Var32(&id);
u32 index = ptr ? (u32)(ptr - &VertexRAM[0]) : UINT32_MAX;
file->Var32(&index);
}
}
else
{
for (int j = 0; j < 10; j++)
{
u32 id = -1;
file->Var32(&id);
if (id == 0xFFFFFFFF) poly->Vertices[j] = NULL;
else poly->Vertices[j] = &VertexRAM[id];
u32 index = UINT32_MAX;
file->Var32(&index);
poly->Vertices[j] = index == UINT32_MAX ? nullptr : &VertexRAM[index];
}
}
@ -495,7 +490,6 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
}
}
// probably not worth storing the vblank-latched Renderxxxxxx variables
CmdStallQueue.DoSavestate(file);
file->Var32((u32*)&VertexPipeline);
@ -511,10 +505,27 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
CurVertexRAM = &VertexRAM[CurRAMBank ? 6144 : 0];
CurPolygonRAM = &PolygonRAM[CurRAMBank ? 2048 : 0];
}
// better safe than sorry, I guess
// might cause a blank frame but atleast it won't shit itself
RenderNumPolygons = 0;
file->Var32(&RenderNumPolygons);
if (file->Saving)
{
for (const Polygon* p : RenderPolygonRAM)
{
u32 index = p ? (p - &PolygonRAM[0]) : UINT32_MAX;
file->Var32(&index);
}
}
else
{
for (int i = 0; i < RenderPolygonRAM.size(); ++i)
{
u32 index = UINT32_MAX;
file->Var32(&index);
RenderPolygonRAM[i] = index == UINT32_MAX ? nullptr : &PolygonRAM[index];
}
}
file->VarArray(CurVertex, sizeof(s16)*3);
@ -534,6 +545,18 @@ void GPU3D::DoSavestate(Savestate* file) noexcept
file->VarArray(ShininessTable, 128*sizeof(u8));
file->Bool32(&AbortFrame);
file->Bool32(&GeometryEnabled);
file->Bool32(&RenderingEnabled);
file->Var32(&PolygonMode);
file->Var32(&PolygonAttr);
file->Var32(&CurPolygonAttr);
file->Var32(&TexParam);
file->Var32(&TexPalette);
RenderFrameIdentical = false;
if (softRenderer && softRenderer->IsThreaded())
{
softRenderer->EnableRenderThread();
}
}

6
src/GPU3D.h
View File

@ -47,6 +47,7 @@ struct Vertex
// TODO maybe: hi-res color? (that survives clipping)
s32 HiresPosition[2];
void DoSavestate(Savestate* file) noexcept;
};
struct Polygon
@ -78,6 +79,7 @@ struct Polygon
u32 SortKey;
void DoSavestate(Savestate* file) noexcept;
};
class Renderer3D;
@ -269,7 +271,7 @@ public:
u32 RenderClearAttr1 = 0;
u32 RenderClearAttr2 = 0;
bool RenderFrameIdentical = false;
bool RenderFrameIdentical = false; // not part of the hardware state, don't serialize
bool AbortFrame = false;
@ -323,7 +325,7 @@ public:
u32 FlushRequest = 0;
u32 FlushAttributes = 0;
u32 ScrolledLine[256];
u32 ScrolledLine[256]; // not part of the hardware state, don't serialize
};
class Renderer3D

57
src/GPU3D_Soft.cpp
View File

@ -34,8 +34,11 @@ void SoftRenderer::StopRenderThread()
{
if (RenderThreadRunning.load(std::memory_order_relaxed))
{
// Tell the render thread to stop drawing new frames, and finish up the current one.
RenderThreadRunning = false;
Platform::Semaphore_Post(Sema_RenderStart);
Platform::Thread_Wait(RenderThread);
Platform::Thread_Free(RenderThread);
RenderThread = nullptr;
@ -47,24 +50,36 @@ void SoftRenderer::SetupRenderThread(GPU& gpu)
if (Threaded)
{
if (!RenderThreadRunning.load(std::memory_order_relaxed))
{
RenderThreadRunning = true;
{ // If the render thread isn't already running...
RenderThreadRunning = true; // "Time for work, render thread!"
RenderThread = Platform::Thread_Create([this, &gpu]() {
RenderThreadFunc(gpu);
});
}
// otherwise more than one frame can be queued up at once
// "Be on standby, but don't start rendering until I tell you to!"
Platform::Semaphore_Reset(Sema_RenderStart);
// "Oh, sorry, were you already in the middle of a frame from the last iteration?"
if (RenderThreadRendering)
// "Tell me when you're done, I'll wait here."
Platform::Semaphore_Wait(Sema_RenderDone);
Platform::Semaphore_Reset(Sema_RenderDone);
Platform::Semaphore_Reset(Sema_RenderStart);
Platform::Semaphore_Reset(Sema_ScanlineCount);
// "All good? Okay, let me give you your training."
// "(Maybe you're still the same thread, but I have to tell you this stuff anyway.)"
Platform::Semaphore_Post(Sema_RenderStart);
// "This is the signal you'll send when you're done with a frame."
// "I'll listen for it when I need to show something to the frontend."
Platform::Semaphore_Reset(Sema_RenderDone);
// "This is the signal I'll send when I want you to start rendering."
// "Don't do anything until you get the message."
Platform::Semaphore_Reset(Sema_RenderStart);
// "This is the signal you'll send every time you finish drawing a line."
// "I might need some of your scanlines before you finish the whole buffer,"
// "so let me know as soon as you're done with each one."
Platform::Semaphore_Reset(Sema_ScanlineCount);
}
else
{
@ -72,6 +87,13 @@ void SoftRenderer::SetupRenderThread(GPU& gpu)
}
}
void SoftRenderer::EnableRenderThread()
{
if (Threaded && Sema_RenderStart)
{
Platform::Semaphore_Post(Sema_RenderStart);
}
}
SoftRenderer::SoftRenderer(bool threaded) noexcept
: Renderer3D(false), Threaded(threaded)
@ -103,6 +125,7 @@ void SoftRenderer::Reset(GPU& gpu)
PrevIsShadowMask = false;
SetupRenderThread(gpu);
EnableRenderThread();
}
void SoftRenderer::SetThreaded(bool threaded, GPU& gpu) noexcept
@ -111,6 +134,7 @@ void SoftRenderer::SetThreaded(bool threaded, GPU& gpu) noexcept
{
Threaded = threaded;
SetupRenderThread(gpu);
EnableRenderThread();
}
}
@ -1692,12 +1716,14 @@ void SoftRenderer::RenderPolygons(const GPU& gpu, bool threaded, Polygon** polyg
ScanlineFinalPass(gpu.GPU3D, y-1);
if (threaded)
// Notify the main thread that we're done with a scanline.
Platform::Semaphore_Post(Sema_ScanlineCount);
}
ScanlineFinalPass(gpu.GPU3D, 191);
if (threaded)
// If this renderer is threaded, notify the main thread that we're done with the frame.
Platform::Semaphore_Post(Sema_ScanlineCount);
}
@ -1719,6 +1745,7 @@ void SoftRenderer::RenderFrame(GPU& gpu)
if (RenderThreadRunning.load(std::memory_order_relaxed))
{
// "Render thread, you're up! Get moving."
Platform::Semaphore_Post(Sema_RenderStart);
}
else if (!FrameIdentical)
@ -1731,18 +1758,26 @@ void SoftRenderer::RenderFrame(GPU& gpu)
void SoftRenderer::RestartFrame(GPU& gpu)
{
SetupRenderThread(gpu);
EnableRenderThread();
}
void SoftRenderer::RenderThreadFunc(GPU& gpu)
{
for (;;)
{
// Wait for a notice from the main thread to start rendering (or to stop entirely).
Platform::Semaphore_Wait(Sema_RenderStart);
if (!RenderThreadRunning) return;
// Protect the GPU state from the main thread.
// Some melonDS frontends (though not ours)
// will repeatedly save or load states;
// if they do so while the render thread is busy here,
// the ensuing race conditions may cause a crash
// (since some of the GPU state includes pointers).
RenderThreadRendering = true;
if (FrameIdentical)
{
{ // If no rendering is needed, just say we're done.
Platform::Semaphore_Post(Sema_ScanlineCount, 192);
}
else
@ -1751,7 +1786,10 @@ void SoftRenderer::RenderThreadFunc(GPU& gpu)
RenderPolygons(gpu, true, &gpu.GPU3D.RenderPolygonRAM[0], gpu.GPU3D.RenderNumPolygons);
}
// Tell the main thread that we're done rendering
// and that it's safe to access the GPU state again.
Platform::Semaphore_Post(Sema_RenderDone);
RenderThreadRendering = false;
}
}
@ -1761,6 +1799,9 @@ u32* SoftRenderer::GetLine(int line)
if (RenderThreadRunning.load(std::memory_order_relaxed))
{
if (line < 192)
// We need a scanline, so let's wait for the render thread to finish it.
// (both threads process scanlines from top-to-bottom,
// so we don't need to wait for a specific row)
Platform::Semaphore_Wait(Sema_ScanlineCount);
}

9
src/GPU3D_Soft.h
View File

@ -42,8 +42,10 @@ public:
u32* GetLine(int line) override;
void SetupRenderThread(GPU& gpu);
void EnableRenderThread();
void StopRenderThread();
private:
friend void GPU3D::DoSavestate(Savestate* file) noexcept;
// Notes on the interpolator:
//
// This is a theory on how the DS hardware interpolates values. It matches hardware output
@ -506,8 +508,15 @@ private:
Platform::Thread* RenderThread;
std::atomic_bool RenderThreadRunning;
std::atomic_bool RenderThreadRendering;
// Used by the main thread to tell the render thread to start rendering a frame
Platform::Semaphore* Sema_RenderStart;
// Used by the render thread to tell the main thread that it's done rendering a frame
Platform::Semaphore* Sema_RenderDone;
// Used to allow the main thread to read some scanlines
// before (the 3D portion of) the entire frame is rasterized.
Platform::Semaphore* Sema_ScanlineCount;
};
}

2
src/Savestate.h
View File

@ -24,7 +24,7 @@
#include <stdio.h>
#include "types.h"
#define SAVESTATE_MAJOR 11
#define SAVESTATE_MAJOR 12
#define SAVESTATE_MINOR 1
namespace melonDS