IOS: Keep copy of m_devices in USBHost

This gets rid of the ugly direct access to USBScanner::m_devices that
was introduced by the previous commit.

This also fixes a potential thread safety issue.
USB_HIDv4::TriggerDeviceChangeReply loops through m_devices and calls
GetDeviceEntry for each device. If USB_HIDv4::TriggerDeviceChangeReply
is called after a new device is added to m_devices but before hooks are
dispatched, GetDeviceEntry crashes, because the hook that's supposed to
update m_device_ids hasn't run yet. With this commit, this issue can no
longer happen, because USBHost::m_devices_mutex doesn't get unlocked in
between updating m_devices and dispatching the hooks.

Source/Core/Core/IOS/USB/Host.cpp

@@ -4,7 +4,9 @@
 #include "Core/IOS/USB/Host.h"
 
 #include <functional>
+#include <map>
 #include <memory>
+#include <mutex>
 #include <optional>
 #include <string>
 
@@ -61,7 +63,11 @@ void USBHost::DoState(PointerWrap& p)
 
 std::shared_ptr<USB::Device> USBHost::GetDeviceById(const u64 device_id) const
 {
-  return m_usb_scanner.GetDeviceById(device_id);
+  std::lock_guard lk(m_devices_mutex);
+  const auto it = m_devices.find(device_id);
+  if (it == m_devices.end())
+    return nullptr;
+  return it->second;
 }
 
 void USBHost::OnDeviceChange(ChangeEvent event, std::shared_ptr<USB::Device> changed_device)
@@ -85,13 +91,22 @@ void USBHost::Update()
 
 void USBHost::DispatchHooks(const DeviceChangeHooks& hooks)
 {
-  for (const auto& hook : hooks)
+  std::lock_guard lk(m_devices_mutex);
+
+  for (const auto& [device, event] : hooks)
   {
     INFO_LOG_FMT(IOS_USB, "{} - {} device: {:04x}:{:04x}", GetDeviceName(),
-                 hook.second == ChangeEvent::Inserted ? "New" : "Removed", hook.first->GetVid(),
+                 event == ChangeEvent::Inserted ? "New" : "Removed", device->GetVid(),
-                 hook.first->GetPid());
+                 device->GetPid());
-    OnDeviceChange(hook.second, hook.first);
+
+    if (event == ChangeEvent::Inserted)
+      m_devices.emplace(device->GetId(), device);
+    else if (event == ChangeEvent::Removed)
+      m_devices.erase(device->GetId());
+
+    OnDeviceChange(event, device);
   }
+
   if (!hooks.empty())
     OnDeviceChangeEnd();
 }

Source/Core/Core/IOS/USB/Host.h

@@ -4,7 +4,9 @@
 #pragma once
 
 #include <functional>
+#include <map>
 #include <memory>
+#include <mutex>
 #include <optional>
 #include <string>
 
@@ -45,6 +47,9 @@ protected:
   std::optional<IPCReply> HandleTransfer(std::shared_ptr<USB::Device> device, u32 request,
                                          std::function<s32()> submit) const;
 
+  std::map<u64, std::shared_ptr<USB::Device>> m_devices;
+  mutable std::recursive_mutex m_devices_mutex;
+
   USBScanner m_usb_scanner{this};
 
 private:

Source/Core/Core/IOS/USB/OH0/OH0.cpp

@@ -73,7 +73,7 @@ std::optional<IPCReply> OH0::IOCtlV(const IOCtlVRequest& request)
 
 void OH0::DoState(PointerWrap& p)
 {
-  if (p.IsReadMode() && !m_usb_scanner.m_devices.empty())
+  if (p.IsReadMode() && !m_devices.empty())
   {
     Core::DisplayMessage("It is suggested that you unplug and replug all connected USB devices.",
                          5000);
@@ -114,8 +114,8 @@ IPCReply OH0::GetDeviceList(const IOCtlVRequest& request) const
 
   const u8 interface_class = memory.Read_U8(request.in_vectors[1].address);
   u8 entries_count = 0;
-  std::lock_guard lk(m_usb_scanner.m_devices_mutex);
+  std::lock_guard lk(m_devices_mutex);
-  for (const auto& device : m_usb_scanner.m_devices)
+  for (const auto& device : m_devices)
   {
     if (entries_count >= max_entries_count)
       break;
@@ -231,14 +231,13 @@ std::optional<IPCReply> OH0::RegisterClassChangeHook(const IOCtlVRequest& reques
 
 bool OH0::HasDeviceWithVidPid(const u16 vid, const u16 pid) const
 {
-  return std::ranges::any_of(m_usb_scanner.m_devices, [=](const auto& device) {
+  return std::ranges::any_of(m_devices, [=](const auto& device) {
     return device.second->GetVid() == vid && device.second->GetPid() == pid;
   });
 }
 
 void OH0::OnDeviceChange(const ChangeEvent event, std::shared_ptr<USB::Device> device)
 {
-  std::lock_guard lk(m_usb_scanner.m_devices_mutex);
   if (event == ChangeEvent::Inserted)
     TriggerHook(m_insertion_hooks, {device->GetVid(), device->GetPid()}, IPC_SUCCESS);
   else if (event == ChangeEvent::Removed)
@@ -259,10 +258,10 @@ void OH0::TriggerHook(std::map<T, u32>& hooks, T value, const ReturnCode return_
 
 std::pair<ReturnCode, u64> OH0::DeviceOpen(const u16 vid, const u16 pid)
 {
-  std::lock_guard lk(m_usb_scanner.m_devices_mutex);
+  std::lock_guard lk(m_devices_mutex);
 
   bool has_device_with_vid_pid = false;
-  for (const auto& device : m_usb_scanner.m_devices)
+  for (const auto& device : m_devices)
   {
     if (device.second->GetVid() != vid || device.second->GetPid() != pid)
       continue;

Source/Core/Core/IOS/USB/USBScanner.h

@@ -32,8 +32,6 @@ public:
   void WaitForFirstScan();
   bool UpdateDevices(bool always_add_hooks = false);
 
-  std::shared_ptr<USB::Device> GetDeviceById(u64 device_id) const;
-
   enum class ChangeEvent
   {
     Inserted,
@@ -41,9 +39,6 @@ public:
   };
   using DeviceChangeHooks = std::map<std::shared_ptr<USB::Device>, ChangeEvent>;
 
-  std::map<u64, std::shared_ptr<USB::Device>> m_devices;
-  mutable std::mutex m_devices_mutex;
-
 private:
   bool AddDevice(std::unique_ptr<USB::Device> device);
   bool AddNewDevices(std::set<u64>& new_devices, DeviceChangeHooks& hooks, bool always_add_hooks);
@@ -53,6 +48,11 @@ private:
   void CheckAndAddDevice(std::unique_ptr<USB::Device> device, std::set<u64>& new_devices,
                          DeviceChangeHooks& hooks, bool always_add_hooks);
 
+  std::shared_ptr<USB::Device> GetDeviceById(u64 device_id) const;
+
+  std::map<u64, std::shared_ptr<USB::Device>> m_devices;
+  mutable std::mutex m_devices_mutex;
+
   USBHost* m_host = nullptr;
   Common::Flag m_thread_running;
   std::thread m_thread;

Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp

@@ -207,10 +207,10 @@ void USB_HIDv4::TriggerDeviceChangeReply()
   auto& memory = system.GetMemory();
 
   {
-    std::lock_guard lk(m_usb_scanner.m_devices_mutex);
+    std::lock_guard lk(m_devices_mutex);
     const u32 dest = m_devicechange_hook_request->buffer_out;
     u32 offset = 0;
-    for (const auto& device : m_usb_scanner.m_devices)
+    for (const auto& device : m_devices)
     {
       const std::vector<u8> device_section = GetDeviceEntry(*device.second.get());
       if (offset + device_section.size() > m_devicechange_hook_request->buffer_out_size - 1)