A drained MpscQueue node goes onto a free stack shared by every queue of the same type, and a
producer takes that stack whole when its own thread's list runs dry, so once warmed up a push
no longer allocates. That takes the heap allocation back off memory block notifications, the
CPU queue, Vulkan deletes and the GL render queue. A unit test runs several producers against
one consumer over two rounds.
The NpSignin dialog's delays run on emulated time and are saved with the state, so the dialog
behaves the same at any speed and under run-ahead. The time since the last save and savestate
goes; only the standalone frontends' exit prompts read it.
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.
libretroadmin