Comment 161 for bug 1690719

The backported input thread patches mainly laid a foundation to solve this issue. Mutter still needs more work to take advantage of the new input thread. That is why there isn't an improvement in GNOME 40.

This is described here: https://blogs.gnome.org/shell-dev/2021/01/21/threaded-input-adventures/

> The main thread is still in charge of KMS, and updating the cursor plane buffer and position. This means the pointer cursor will still freeze if the main thread stalled, despite the input thread handling events underneath. In the future, There would be another separate thread handling atomic KMS operations, so it’d be possible for the input and KMS threads to talk between them and bypassing any main thread stalls.