[PATCH] rtl8187: Fix lockups due to concurrent access to config routine

[Larry Finger <Larry.Finger@lwfinger.net>]

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.

The problem was found by Herton Ronaldo Krzesinski <herton@mandriva.com.br>,
who also suggested this type of fix.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
---

John,

This is 2.6.27 material as it fixes a bug.

Larry
---


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 +94,10 @@ struct rtl8187_priv {
  	const struct rtl818x_rf_ops *rf;
  	struct ieee80211_vif *vif;
  	int mode;
+	/* The mutex protects the TX loopback state.
+	 * Any attempt to set channels concurrently locks the device.
+	 */
+	struct mutex conf_mutex;

  	/* 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->conf_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->conf_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->conf_mutex);

  	printk(KERN_INFO "%s: hwaddr %s, %s V%d + %s\n",
  	       wiphy_name(dev->wiphy), print_mac(mac, dev->wiphy->perm_addr),