Re: [core-for-CI PATCH] usb: typec: ucsi: Fix a potential deadlock in ucsi_send_command_common()

["Coelho, Luciano" <luciano.coelho@intel.com>]

On Wed, 2024-08-07 at 11:57 +0530, Chaitanya Kumar Borah wrote:
> From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> 
> The function returns with the ppm_lock held if there's an
> error or the PPM reports BUSY condition.
> 
> This is a core-for-ci patch for [1]
> 
> [1] https://lore.kernel.org/linux-usb/20240806112029.2984319-1-heikki.krogerus@linux.intel.com/
> 
> Reported-by: Luciano Coelho <luciano.coelho@intel.com>
> Fixes: 5e9c1662a89b ("usb: typec: ucsi: rework command execution functions")
> References: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11849
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
>  drivers/usb/typec/ucsi/ucsi.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index dcd3765cc1f5..432a2d6266d7 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -238,13 +238,10 @@ static int ucsi_send_command_common(struct ucsi *ucsi, u64 cmd,
>  	mutex_lock(&ucsi->ppm_lock);
>  
>  	ret = ucsi_run_command(ucsi, cmd, &cci, data, size, conn_ack);
> -	if (cci & UCSI_CCI_BUSY) {
> -		ret = ucsi_run_command(ucsi, UCSI_CANCEL, &cci, NULL, 0, false);
> -		return ret ? ret : -EBUSY;
> -	}
> -
> -	if (cci & UCSI_CCI_ERROR)
> -		return ucsi_read_error(ucsi, connector_num);
> +	if (cci & UCSI_CCI_BUSY)
> +		ret = ucsi_run_command(ucsi, UCSI_CANCEL, &cci, NULL, 0, false) ?: -EBUSY;
> +	else if (cci & UCSI_CCI_ERROR)
> +		ret = ucsi_read_error(ucsi, connector_num);
>  
>  	mutex_unlock(&ucsi->ppm_lock);
>  	return ret;

This is not the exact patch that was sent upstream, where Heikki
changed my Reported-by to Reported-and-Tested-by (at least).  I think
the best is to have the patch that was actually sent upstream, because
it's easier to match later on, when it gets merged in the mainline.

In any case, I think this can be merged as is, so:

Acked-by: Luca Coelho <luciano.coelho@intel.com>

--
Cheers,
Luca.