The core and the headless tools no longer use mutexes, condition variables,
spinlocks, std::atomic, std::thread or volatile flags. Threads hand off through
libretro-common's retro_atomic and rthreads plus a few small pieces on top of
them in Common/Thread: Thread, MpscQueue, EventCounter, ParkingLot waits and
ReaderGate. Every wait blocks until it's woken; nothing polls on a timer.
State that only one thread touches just loses its lock. The PSP filesystem,
sceIo and the savedata dialog now belong to the emulation thread: async reads
and writes run when they're queued and complete later in emulated time, and
the IO and savedata threads are gone. The friend finder only talks to the
adhoc server and hands what it gets to the emulation thread. GPU init always
runs on the thread that starts the game.
The Vulkan render and compile queues, pipeline and render pass caches, delete
list and SPIR-V cache, the GL render queue, the software renderer's jit caches,
the file loader caches, the web debugger, UPnP, input, savestates, logging and
the GE debugger all hand off through queues and atomics. The IR jit's spinning
profiler thread goes.
A CPU thread with nothing to run now sleeps until work is queued instead of
spinning. Headless with --debugger waits for a client while stopped, and ends
the run once every client that connected has left. Web server shutdown keeps
servicing the CPU queue until the server has finished.
These own GPU objects, memory or refcounts in their destructors (or assert
there that they were torn down), so a copy would double-free. Nothing copies
them today; this keeps it that way. The manager base classes cover every
backend's subclass.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
GetRenderPass() looks up and inserts into renderPasses_ from the main thread
(EndCurRenderStep, CreateGraphicsPipeline) and from the render thread
(PerformBindFramebufferAsRenderTarget), unsynchronized. The render thread really
does insert rather than only hit: PreprocessSteps rewrites the load actions to
CLEAR when it merges a clear-only pass into a later one, after the main thread
already looked up the pre-merge key. DenseHashMap::Insert can Grow(), which
reallocates the buckets out from under a concurrent Get().
VKRRenderPass::Get() has the same problem one level down - it creates the passes
lazily and is called from both threads on the same object, so two threads hitting
an empty slot each create a pass and one gets overwritten and leaked, while the
sample-count branch can queue a pass for deletion that the other thread is about
to hand to vkCreateGraphicsPipelines.
A mutex each. Handing the VKRRenderPass pointer out from under the map lock is
fine, entries are only ever erased all at once in DestroyDeviceObjects.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vd8ntC2brCUtCrDJMqLbs8
Haven't been using these for a while.
I've come to the conclusion here that I think it's better to try to
deal with the issues using safe workarounds like copies, instead of
relying on features with somewhat iffy driver support that are not
universal across APIs anyway.
libretroadmin