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https://github.com/hrydgard/ppsspp.git
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libretroadmin
f1208a7a5a
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.
100 lines
2.7 KiB
C++
100 lines
2.7 KiB
C++
#pragma once
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#include <cstdint>
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#include <retro_atomic.h>
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#include <rthreads/retro_eventcount.h>
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// Parking for one-shot and counter waits, keyed by address.
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//
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// The eventcounts live for the whole process, sharded by address, so the object being
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// waited on never owns one. A notifier only hashes the address after publishing, it never
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// dereferences it, so a waiter may free the object the moment its predicate holds.
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// Shards are shared, so a wakeup may be for someone else: callers always loop on their
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// own predicate (the helpers below do).
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retro_eventcount_t *ParkingLotFor(const void *addr);
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inline void ParkingLotNotify(const void *addr) {
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retro_eventcount_notify(ParkingLotFor(addr));
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}
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// Blocks until pred() is true.
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template <class Pred>
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inline void ParkingLotWait(const void *addr, Pred pred) {
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if (pred())
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return;
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retro_eventcount_t *ec = ParkingLotFor(addr);
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for (;;) {
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const int key = retro_eventcount_prepare_wait(ec);
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if (pred()) {
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retro_eventcount_cancel_wait(ec);
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return;
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}
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retro_eventcount_commit_wait(ec, key);
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if (pred())
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return;
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}
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}
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// A count of events, for "wait until something happened since I last looked". A waiter reads
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// Seen() before it checks its own state, and Wait(seen) returns once Notify() has run since.
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class EventCounter {
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public:
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EventCounter() {
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retro_atomic_int_init(&count_, 0);
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}
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int Seen() const {
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return retro_atomic_load_acquire_int(const_cast<retro_atomic_int_t *>(&count_));
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}
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// Any thread, after publishing whatever the waiters look at.
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void Notify() {
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retro_atomic_fetch_add_int(&count_, 1);
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ParkingLotNotify(this);
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}
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void Wait(int seen) const {
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ParkingLotWait(this, [&] { return Seen() != seen; });
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}
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private:
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retro_atomic_int_t count_;
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};
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// Grace period for read-mostly pointers: readers bracket each use with
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// Enter/Exit, a writer unpublishes and then Drain()s before freeing.
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// Readers never wait. Drain waits only for readers already inside.
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struct ReaderGate {
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ReaderGate() {
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retro_atomic_int_init(&readers_, 0);
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retro_atomic_int_init(&draining_, 0);
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}
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void Enter() {
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retro_atomic_fetch_add_int(&readers_, 1);
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retro_atomic_thread_fence_seq_cst();
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}
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void Exit() {
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if (retro_atomic_fetch_sub_int(&readers_, 1) == 1) {
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retro_atomic_thread_fence_seq_cst();
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if (retro_atomic_load_relaxed_int(&draining_))
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ParkingLotNotify(this);
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}
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}
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// Call after unpublishing. Only one drainer at a time.
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void Drain() {
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retro_atomic_store_relaxed_int(&draining_, 1);
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retro_atomic_thread_fence_seq_cst();
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ParkingLotWait(this, [this] { return retro_atomic_load_acquire_int(&readers_) == 0; });
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retro_atomic_store_relaxed_int(&draining_, 0);
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}
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private:
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retro_atomic_int_t readers_;
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retro_atomic_int_t draining_;
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};
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