Re: [PATCH] Input: uinput - fix circular locking dependency with ff-core

[mikhail.v.gavrilov@gmail.com]

On Sun, 2026-03-01 at 03:36 +0500, Mikhail Gavrilov wrote:
> A lockdep circular locking dependency warning can be triggered
> reproducibly when using a force-feedback gamepad with uinput (for
> example, playing ELDEN RING under Wine with a Flydigi Vader 5
> controller):
> 
>   ff->mutex -> udev->mutex -> input_mutex -> dev->mutex -> ff->mutex
> 
> The cycle is caused by four lock acquisition paths:
> 
> 1. ff upload: input_ff_upload() holds ff->mutex and calls
>    uinput_dev_upload_effect() -> uinput_request_submit() ->
>    uinput_request_send(), which acquires udev->mutex.
> 
> 2. device create: uinput_ioctl_handler() holds udev->mutex and calls
>    uinput_create_device() -> input_register_device(), which acquires
>    input_mutex.
> 
> 3. device register: input_register_device() holds input_mutex and
>    calls kbd_connect() -> input_register_handle(), which acquires
>    dev->mutex.
> 
> 4. evdev release: evdev_release() calls input_flush_device() under
>    dev->mutex, which calls input_ff_flush() acquiring ff->mutex.
> 
> 
> 
Hi Dmitry,

Friendly ping on this patch. It fixes a reproducible lockdep circular
dependency warning in uinput with force-feedback gamepads under
Wine/Proton, tested on 7.0-rc1.

I realize I should have included:

  Fixes: ff462551235d ("Input: uinput - switch to the new FF
interface")
  Cc: stable@vger.kernel.org

Should I resend as v2 with these tags, or can you add them when
applying?

-- 
Best Regards,
Mike Gavrilov.