Re: [RFC/RFT] rtl8187: Protect the config callback from mac80211 with a mutex

[Michael Buesch <mb@bu3sch.de>]

On Wednesday 30 July 2008 08:12:36 Larry Finger wrote:
> Herton,
> 
> Does this patch help your problem? I haven't done much testing, but things seem 
> to be better with it here.
> 
> Larry
> 
> ==================
> 
> Some users of the RTL8187B have experienced difficulties since commit
> 8f87dd7e540d455f8e7f11478133b85edc969c67 that introduced the power
> management wext hooks. This difficulty has not made much sense until
> it was realized that it was possible for mac80211 to make a call to the
> config routine while that routine was already being executed. This patch
> protects the critical section with a mutex.
> 
> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
> ---
> 
> Index: wireless-testing/drivers/net/wireless/rtl8187.h
> ===================================================================
> --- wireless-testing.orig/drivers/net/wireless/rtl8187.h
> +++ wireless-testing/drivers/net/wireless/rtl8187.h
> @@ -94,6 +94,7 @@ struct rtl8187_priv {
>   	const struct rtl818x_rf_ops *rf;
>   	struct ieee80211_vif *vif;
>   	int mode;
> +	struct mutex mutex;	/* used to lock config callback */

Well, hm.
Using locks to protect code is a bad idea, most of the time.
So that comment makes no sense.

What that lock _probably_ does it to protect the configuration
data in struct rtl8187_priv. So you'd better find out which data
that is and clarify the comment.

> 
>   	/* rtl8187 specific */
>   	struct ieee80211_channel channels[14];
> Index: wireless-testing/drivers/net/wireless/rtl8187_dev.c
> ===================================================================
> --- wireless-testing.orig/drivers/net/wireless/rtl8187_dev.c
> +++ wireless-testing/drivers/net/wireless/rtl8187_dev.c
> @@ -864,6 +864,7 @@ static int rtl8187_config(struct ieee802
>   	struct rtl8187_priv *priv = dev->priv;
>   	u32 reg;
> 
> +	mutex_lock(&priv->mutex);
>   	reg = rtl818x_ioread32(priv, &priv->map->TX_CONF);
>   	/* Enable TX loopback on MAC level to avoid TX during channel
>   	 * changes, as this has be seen to causes problems and the
> @@ -896,6 +897,7 @@ static int rtl8187_config(struct ieee802
>   	rtl818x_iowrite16(priv, &priv->map->ATIMTR_INTERVAL, 100);
>   	rtl818x_iowrite16(priv, &priv->map->BEACON_INTERVAL, 100);
>   	rtl818x_iowrite16(priv, &priv->map->BEACON_INTERVAL_TIME, 100);
> +	mutex_unlock(&priv->mutex);
>   	return 0;
>   }
> 
> @@ -1187,6 +1189,7 @@ static int __devinit rtl8187_probe(struc
>   		printk(KERN_ERR "rtl8187: Cannot register device\n");
>   		goto err_free_dev;
>   	}
> +	mutex_init(&priv->mutex);
> 
>   	printk(KERN_INFO "%s: hwaddr %s, %s V%d + %s\n",
>   	       wiphy_name(dev->wiphy), print_mac(mac, dev->wiphy->perm_addr),

-- 
Greetings Michael.