linux-kernel - Re: [PATCH 1/2] usb: typec: ucsi: displayport: Fix deadlock

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Message-ID: <Z_ds09xFjwedjTam@kuha.fi.intel.com>
Date: Thu, 10 Apr 2025 10:01:39 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Andrei Kuchynski <akuchynski@...omium.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jameson Thies <jthies@...gle.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>,
	Pooja Katiyar <pooja.katiyar@...el.com>,
	Madhu M <madhu.m@...el.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: typec: ucsi: displayport: Fix deadlock

Hi Andrei,

> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -1922,6 +1922,42 @@ void ucsi_set_drvdata(struct ucsi *ucsi, void *data)
>  }
>  EXPORT_SYMBOL_GPL(ucsi_set_drvdata);
>  
> +/**
> + * ucsi_con_mutex_lock - Acquire the connector mutex
> + * @con: The connector interface to lock
> + *
> + * Returns true on success, false if the connector is disconnected
> + */
> +bool ucsi_con_mutex_lock(struct ucsi_connector *con)
> +{
> +	bool mutex_locked = false;
> +	bool connected = true;
> +
> +	while (connected && !mutex_locked) {
> +		mutex_locked = mutex_trylock(&con->lock) != 0;
> +		connected = UCSI_CONSTAT(con, CONNECTED);
> +		if (connected && !mutex_locked)
> +			msleep(20);
> +	}
> +
> +	connected = connected && con->partner;
> +	if (!connected && mutex_locked)
> +		mutex_unlock(&con->lock);
> +
> +	return connected;
> +}
> +EXPORT_SYMBOL_GPL(ucsi_con_mutex_lock);
> +
> +/**
> + * ucsi_con_mutex_unlock - Release the connector mutex
> + * @con: The connector interface to unlock
> + */
> +void ucsi_con_mutex_unlock(struct ucsi_connector *con)
> +{
> +	mutex_unlock(&con->lock);
> +}
> +EXPORT_SYMBOL_GPL(ucsi_con_mutex_unlock);

No need to export these.

thanks,

-- 
heikki