Remove the redundant s_populate_mutex and only use
ControllerInterface::m_devices_population_mutex instead to prevent a
deadlock caused by locking them in opposite orders.
The device population functions in the win32 InputBackend previously
locked s_populate_mutex first before calling various functions that
locked m_devices_population_mutex. This normally worked but
ControllerInterface::RefreshDevices locks m_devices_population_mutex
first and then calls HandleWindowChange which then locked
s_populate_mutex, potentially causing the deadlock.
Fix this by using PlatformPopulateDevices to lock
m_devices_population_mutex before running the code that was previously
protected by s_populate_mutex. The functions in question lock
m_devices_population_mutex anyway, so this shouldn't meaningfully
increase contention on the lock.
Reproduction steps:
* Let Dolphin finish startup.
* In Win32.cpp::OnDevicesChanged set a breakpoint on the call to
PlatformPopulateDevices. When the breakpoint is triggered the function
will have locked s_populate_mutex, but since PlatformPopulateDevices
won't have run yet m_devices_population_mutex will still be unlocked.
* Unplug a device from your computer.
* Wait for the breakpoint to trigger. (At this point you can plug the
device back in).
* Freeze the ntdll.dll!TppWorkerThread() that triggered the breakpoint.
* Resume Dolphin and start a game.
* Core::EmuThread will call ControllerInterface::ChangeWindow which
calls RefreshDevices. It locks m_devices_population_mutex, then calls
InputBackend::HandleWindowChange, which tries to lock
s_populate_mutex.
* Unfreeze ntdll.dll!TppWorkerThread().
At this point EmuThread and TppWorkerThread are deadlocked. The UI is
still responsive since the Host thread is unaffected, but trying to stop
the game or close Dolphin normally will fail since EmuThread is unable
to stop.
Fixes bug: https://bugs.dolphin-emu.org/issues/12744
Before e1e3db13ba
the ControllerInterface m_devices_mutex was "wrongfully" locked for the whole Initialize() call, which included the first device population refresh,
this has the unwanted (accidental) consequence of often preventing the different pads (GC Pad, Wii Contollers, ...) input configs from loading
until that mutex was released (the input config defaults loading was blocked in EmulatedController::LoadDefaults()), which meant that the devices
population would often have the time to finish adding its first device, which would then be selected as default device (by design, the first device
added to the CI is the default default device, usually the "Keyboard and Mouse" device).
After the commit mentioned above removed the unnecessary m_devices_mutex calls, the default default device would fail to load (be found)
causing the default input mappings, which are specifically written for the default default device on every platform, to not be bound to any
physical device input, breaking input on new dolphin installations (until a user tried to customize the default device manually).
Default devices are now always added synchronously to avoid the problem, and so they should in the future (I added comments and warnings to help with that)
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Make sure m_is_populating_devices is true when a WM_INPUT_DEVICE_CHANGE
event is received directly on the ciface thread, so that callbacks do
not occur while removing devices. This breaks a hold-and-wait deadlock
between the ciface thread and the CPU thread when using emulated
Wiimotes.
Co-authored-by: brainleq <brainleq@users.noreply.github.com>
Co-authored-by: oldmud0 <oldmud0@users.noreply.github.com>
Dentomologist