Don't call RunAsCPUThread in config callbacks

In theory, our config system supports calling Set from any thread. But
because we have config callbacks that call RunAsCPUThread, it's a lot
more restricted in practice. Calling Set from any thread other than the
host thread or the CPU thread is formally thread unsafe, and calling Set
on the host thread while the CPU thread is showing a panic alert causes
a deadlock. This is especially a problem because 04072f0 made the
"Ignore for this session" button in panic alerts call Set.

Because so many of our config callbacks want their code to run on the
CPU thread, I thought it would make sense to have a centralized way to
move execution to the CPU thread for config callbacks. To solve the
deadlock problem, this new way is non-blocking. This means that threads
other than the CPU thread might continue executing before the CPU thread
is informed of the new config, but I don't think there's any problem
with that.

Intends to fix https://bugs.dolphin-emu.org/issues/13108.

1 files changed, 2 insertions, 1 deletions

diff --git a/Source/Core/Common/Config/Config.h b/Source/Core/Common/Config/Config.h
index b448f234f9..4d770ee36e 100644
--- a/Source/Core/Common/Config/Config.h
+++ b/Source/Core/Common/Config/Config.h
@@ -22,7 +22,8 @@ void AddLayer(std::unique_ptr<ConfigLayerLoader> loader);
 std::shared_ptr<Layer> GetLayer(LayerType layer);
 void RemoveLayer(LayerType layer);
 
-// returns an ID that can be passed to RemoveConfigChangedCallback()
+// Returns an ID that can be passed to RemoveConfigChangedCallback().
+// The callback may be called from any thread.
 size_t AddConfigChangedCallback(ConfigChangedCallback func);
 void RemoveConfigChangedCallback(size_t callback_id);
 void OnConfigChanged();