Linux Ethernet Bridging - Aug 2007 - [Bridge] Re: BUG: when using 'brctl stp'

Bridge locking for /sys/class/net/br0/bridge/stp_enabled
was wrong.  Another bug in bridge utilities makes it such that
this interface, meant it wasn't being used.  The locking needs to be removed
from set_stp_state(), the lock is already acquired down in
br_stp_start()/br_stp_stop.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>


--- a/net/bridge/br_sysfs_br.c	2007-07-16 14:24:18.000000000 +0100
+++ b/net/bridge/br_sysfs_br.c	2007-08-14 13:44:23.000000000 +0100
@@ -150,9 +150,7 @@ static ssize_t show_stp_state(struct dev
 static void set_stp_state(struct net_bridge *br, unsigned long val)
 {
 	rtnl_lock();
-	spin_unlock_bh(&br->lock);
 	br_stp_set_enabled(br, val);
-	spin_lock_bh(&br->lock);
 	rtnl_unlock();
 }

On Tue, Aug 14, 2007 at 02:11:05PM +0100, Stephen Hemminger wrote:
> Bridge locking for /sys/class/net/br0/bridge/stp_enabled
> was wrong.  Another bug in bridge utilities makes it such that
> this interface, meant it wasn't being used.  The locking needs
> to be removed from set_stp_state(), the lock is already acquired
> down in br_stp_start()/br_stp_stop.
The 'locking' in set_stp_state() is actually dropping the lock
around the br_stp_set_enabled() invocation, not acquiring it:

> @@ -150,9 +150,7 @@ static ssize_t show_stp_state(struct dev
>  static void set_stp_state(struct net_bridge *br, unsigned long val)
>  {
>  	rtnl_lock();
> -	spin_unlock_bh(&br->lock);
>  	br_stp_set_enabled(br, val);
> -	spin_lock_bh(&br->lock);
>  	rtnl_unlock();
>  }

Forget earlier patch, it is wrong...

The stp change code generates "sleeping function called from invalid
context"
because rtnl_lock() called with BH disabled. This fixes it by not acquiring then
dropping the bridge lock.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>

--- a/net/bridge/br_sysfs_br.c	2007-08-06 09:26:48.000000000 +0100
+++ b/net/bridge/br_sysfs_br.c	2007-08-14 14:29:52.000000000 +0100
@@ -147,20 +147,26 @@ static ssize_t show_stp_state(struct dev
 	return sprintf(buf, "%d\n", br->stp_enabled);
 }
 
-static void set_stp_state(struct net_bridge *br, unsigned long val)
-{
-	rtnl_lock();
-	spin_unlock_bh(&br->lock);
-	br_stp_set_enabled(br, val);
-	spin_lock_bh(&br->lock);
-	rtnl_unlock();
-}
 
 static ssize_t store_stp_state(struct device *d,
 			       struct device_attribute *attr, const char *buf,
 			       size_t len)
 {
-	return store_bridge_parm(d, buf, len, set_stp_state);
+	struct net_bridge *br = to_bridge(d);
+	char *endp;
+	unsigned long val;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	val = simple_strtoul(buf, &endp, 0);
+	if (endp == buf)
+		return -EINVAL;
+
+	rtnl_lock();
+	br_stp_set_enabled(br, val);
+	rtnl_unlock();
+
 }
 static DEVICE_ATTR(stp_state, S_IRUGO | S_IWUSR, show_stp_state,
 		   store_stp_state);

From: Stephen Hemminger <shemminger@linux-foundation.org>
Date: Tue, 14 Aug 2007 14:50:52 +0100
> Forget earlier patch, it is wrong...
> 
> The stp change code generates "sleeping function called from invalid
context"
> because rtnl_lock() called with BH disabled. This fixes it by not acquiring
then
> dropping the bridge lock.
> 
> Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Applied, thanks Stephen.