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metal: Make the command buffer hold a reference to its fence

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METAL_ReleaseFence cleared the fence's MTLCommandBuffer without holding
submitLock, while METAL_Submit's cleanup loop may still be polling it
through submittedCommandBuffers. It also did so before the DecRef, so
any non-final release broke later waits on a still-owned fence.

(cherry picked from commit d8451e52d5)
This commit is contained in:
William Horvath
2026-09-02 23:47:31 +09:00
committed by Sam Lantinga
parent 39664f3b77
commit 51ef86a11f
1 changed files with 8 additions and 11 deletions
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19
src/gpu/metal/SDL_gpu_metal.m
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@@ -602,7 +602,6 @@ typedef struct MetalCommandBuffer
// Fences
MetalFence *fence;
bool autoReleaseFence;
// Reference Counting
MetalBuffer **usedBuffers;
@@ -2156,8 +2155,6 @@ static SDL_GPUCommandBuffer *METAL_AcquireCommandBuffer(
commandBuffer->computeUniformBuffers[i] = NULL;
}
commandBuffer->autoReleaseFence = true;
SDL_UnlockMutex(renderer->acquireCommandBufferLock);
return (SDL_GPUCommandBuffer *)commandBuffer;
@@ -3400,8 +3397,9 @@ static void METAL_ReleaseFence(
SDL_GPUFence *fence)
{
MetalFence *metalFence = (MetalFence *)fence;
metalFence->commandBuffer = nil;
if (SDL_AtomicDecRef(&metalFence->referenceCount)) {
// Nothing references the fence anymore, so the command buffer can go too.
metalFence->commandBuffer = nil;
METAL_INTERNAL_ReleaseFenceToPool(
(MetalRenderer *)driverData,
(MetalFence *)fence);
@@ -3507,8 +3505,9 @@ static void METAL_INTERNAL_CleanCommandBuffer(
commandBuffer->needComputeReadOnlyStorageTextureBind = false;
SDL_zeroa(commandBuffer->needComputeUniformBufferBind);
// The fence is now available (unless SubmitAndAcquireFence was called)
if (commandBuffer->autoReleaseFence) {
// Drop the command buffer's reference to the fence. A cancelled
// command buffer never acquired one.
if (!cancel) {
METAL_ReleaseFence(
(SDL_GPURenderer *)renderer,
(SDL_GPUFence *)commandBuffer->fence);
@@ -4078,9 +4077,10 @@ static bool METAL_INTERNAL_Submit(
return false;
}
// Return the fence while submitLock is held, another thread could
// recycle this command buffer as soon as the lock is released.
// Give the caller its own reference while submitLock is held, another
// thread could recycle this command buffer as soon as the lock is released.
if (fence) {
(void)SDL_AtomicIncRef(&metalCommandBuffer->fence->referenceCount);
*fence = (SDL_GPUFence *)metalCommandBuffer->fence;
}
@@ -4139,9 +4139,7 @@ static bool METAL_Submit(
static SDL_GPUFence *METAL_SubmitAndAcquireFence(
SDL_GPUCommandBuffer *commandBuffer)
{
MetalCommandBuffer *metalCommandBuffer = (MetalCommandBuffer *)commandBuffer;
SDL_GPUFence *fence = NULL;
metalCommandBuffer->autoReleaseFence = false;
if (!METAL_INTERNAL_Submit(commandBuffer, &fence)) {
return NULL;
}
@@ -4154,7 +4152,6 @@ static bool METAL_Cancel(
MetalCommandBuffer *metalCommandBuffer = (MetalCommandBuffer *)commandBuffer;
MetalRenderer *renderer = metalCommandBuffer->renderer;
metalCommandBuffer->autoReleaseFence = false;
SDL_LockMutex(renderer->submitLock);
METAL_INTERNAL_CleanCommandBuffer(renderer, metalCommandBuffer, true);
SDL_UnlockMutex(renderer->submitLock);