over-eager locking meant kmalloc at GFP_KERNEL with irqs disabled

diff -r b65a76ffb4bb drivers/xen/netfront/accel.c
--- a/drivers/xen/netfront/accel.c	Tue Dec 18 13:11:39 2007 +0000
+++ b/drivers/xen/netfront/accel.c	Thu Dec 20 11:21:09 2007 +0000
@@ -273,6 +273,7 @@ static int init_accelerator(const char *
 {
 	struct netfront_accelerator *accelerator = 
 		kmalloc(sizeof(struct netfront_accelerator), GFP_KERNEL);
+	unsigned long flags;
 	int frontend_len;
 
 	if (!accelerator) {
@@ -294,7 +295,9 @@ static int init_accelerator(const char *
 
 	accelerator->hooks = hooks;
 
+	spin_lock_irqsave(&accelerators_lock, flags);
 	list_add(&accelerator->link, &accelerators_list);
+	spin_unlock_irqrestore(&accelerators_lock, flags);
 
 	*result = accelerator;
 
@@ -365,11 +368,8 @@ static int netfront_load_accelerator(str
 {
 	struct netfront_accelerator *accelerator;
 	int rc = 0;
-	unsigned long flags;
 
 	DPRINTK(" %s\n", frontend);
-
-	spin_lock_irqsave(&accelerators_lock, flags);
 
 	/* 
 	 * Look at list of loaded accelerators to see if the requested
@@ -377,8 +377,6 @@ static int netfront_load_accelerator(str
 	 */
 	list_for_each_entry(accelerator, &accelerators_list, link) {
 		if (match_accelerator(frontend, accelerator)) {
-			spin_unlock_irqrestore(&accelerators_lock, flags);
-
 			accelerator_probe_new_vif(np, dev, accelerator);
 			return 0;
 		}
@@ -386,11 +384,8 @@ static int netfront_load_accelerator(str
 
 	/* Couldn't find it, so create a new one and load the module */
 	if ((rc = init_accelerator(frontend, &accelerator, NULL)) < 0) {
-		spin_unlock_irqrestore(&accelerators_lock, flags);
 		return rc;
 	}
-
-	spin_unlock_irqrestore(&accelerators_lock, flags);
 
 	/* Include this frontend device on the accelerator's list */
 	add_accelerator_vif(accelerator, np);
@@ -450,7 +445,6 @@ int netfront_accelerator_loaded(int vers
 				struct netfront_accel_hooks *hooks)
 {
 	struct netfront_accelerator *accelerator;
-	unsigned long flags;
 
 	if (version != NETFRONT_ACCEL_VERSION) {
 		if (version > NETFRONT_ACCEL_VERSION) {
@@ -469,18 +463,13 @@ int netfront_accelerator_loaded(int vers
 
 	mutex_lock(&accelerator_mutex);
 
-	spin_lock_irqsave(&accelerators_lock, flags);
-
 	/* 
 	 * Look through list of accelerators to see if it has already
 	 * been requested
 	 */
 	list_for_each_entry(accelerator, &accelerators_list, link) {
 		if (match_accelerator(frontend, accelerator)) {
-			spin_unlock_irqrestore(&accelerators_lock, flags);
-
 			accelerator_probe_vifs(accelerator, hooks);
-
 			goto out;
 		}
 	}
@@ -493,8 +482,6 @@ int netfront_accelerator_loaded(int vers
 		frontend);
 
 	init_accelerator(frontend, &accelerator, hooks);
-
-	spin_unlock_irqrestore(&accelerators_lock, flags);
 
  out:
 	mutex_unlock(&accelerator_mutex);