citra-nightly/src/core/hle/kernel/server_session.cpp
Subv e90daa6a4f Kernel/IPC: Add a small delay after each SyncRequest to prevent thread starvation.
In a real 3DS, threads that call svcSyncRequest are put to sleep until the server responds via svcReplyAndReceive. Our HLE services don't implement this mechanism and are effectively immediate from the 3DS's point of view. This commit makes it so that we at least simulate the IPC delay.

Specific HLE handlers might need to put their callers to sleep for a longer period of time to simulate IO timings. This is their responsibility but doing so is currently not implemented.

See https://gist.github.com/ds84182/4a7690c5376e045cab9129ca4185bbeb for a test that was not passing before this commit.
2017-12-07 22:40:15 -05:00

118 lines
4.4 KiB
C++

// Copyright 2016 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <tuple>
#include "core/hle/kernel/client_port.h"
#include "core/hle/kernel/client_session.h"
#include "core/hle/kernel/hle_ipc.h"
#include "core/hle/kernel/server_session.h"
#include "core/hle/kernel/session.h"
#include "core/hle/kernel/thread.h"
namespace Kernel {
ServerSession::ServerSession() = default;
ServerSession::~ServerSession() {
// This destructor will be called automatically when the last ServerSession handle is closed by
// the emulated application.
// Decrease the port's connection count.
if (parent->port)
parent->port->active_sessions--;
// TODO(Subv): Wake up all the ClientSession's waiting threads and set
// the SendSyncRequest result to 0xC920181A.
parent->server = nullptr;
}
ResultVal<SharedPtr<ServerSession>> ServerSession::Create(std::string name) {
SharedPtr<ServerSession> server_session(new ServerSession);
server_session->name = std::move(name);
server_session->parent = nullptr;
return MakeResult(std::move(server_session));
}
bool ServerSession::ShouldWait(Thread* thread) const {
// Closed sessions should never wait, an error will be returned from svcReplyAndReceive.
if (parent->client == nullptr)
return false;
// Wait if we have no pending requests, or if we're currently handling a request.
return pending_requesting_threads.empty() || currently_handling != nullptr;
}
void ServerSession::Acquire(Thread* thread) {
ASSERT_MSG(!ShouldWait(thread), "object unavailable!");
// If the client endpoint was closed, don't do anything. This ServerSession is now useless and
// will linger until its last handle is closed by the running application.
if (parent->client == nullptr)
return;
// We are now handling a request, pop it from the stack.
ASSERT(!pending_requesting_threads.empty());
currently_handling = pending_requesting_threads.back();
pending_requesting_threads.pop_back();
}
ResultCode ServerSession::HandleSyncRequest(SharedPtr<Thread> thread) {
// The ServerSession received a sync request, this means that there's new data available
// from its ClientSession, so wake up any threads that may be waiting on a svcReplyAndReceive or
// similar.
// If this ServerSession has an associated HLE handler, forward the request to it.
if (hle_handler != nullptr) {
hle_handler->HandleSyncRequest(SharedPtr<ServerSession>(this));
}
if (thread->status == THREADSTATUS_RUNNING) {
// Put the thread to sleep until the server replies, it will be awoken in
// svcReplyAndReceive for LLE servers.
thread->status = THREADSTATUS_WAIT_IPC;
if (hle_handler != nullptr) {
// For HLE services, we put the request threads to sleep for a short duration to
// simulate IPC overhead, but only if the HLE handler didn't put the thread to sleep for
// other reasons like an async callback. The IPC overhead is needed to prevent
// starvation when a thread only does sync requests to HLE services while a
// lower-priority thread is waiting to run.
// TODO(Subv): Figure out a good value for this.
static constexpr u64 IPCDelayNanoseconds = 100;
thread->WakeAfterDelay(IPCDelayNanoseconds);
} else {
// Add the thread to the list of threads that have issued a sync request with this
// server.
pending_requesting_threads.push_back(std::move(thread));
}
}
// If this ServerSession does not have an HLE implementation, just wake up the threads waiting
// on it.
WakeupAllWaitingThreads();
return RESULT_SUCCESS;
}
ServerSession::SessionPair ServerSession::CreateSessionPair(const std::string& name,
SharedPtr<ClientPort> port) {
auto server_session = ServerSession::Create(name + "_Server").Unwrap();
SharedPtr<ClientSession> client_session(new ClientSession);
client_session->name = name + "_Client";
std::shared_ptr<Session> parent(new Session);
parent->client = client_session.get();
parent->server = server_session.get();
parent->port = port;
client_session->parent = parent;
server_session->parent = parent;
return std::make_tuple(std::move(server_session), std::move(client_session));
}
} // namespace Kernel