Please find attached a patch that fixes a bug in the netback
acceleration code. There was a call to xenbus_read() while a spinlock
was held, and as xenbus_read() can block this was clearly wrong. The
spinlock is replaced by a mutex.
If this bug fix can weasel its way into 3.2.0 that would be great.
Signed-off-by: Kieran Mansley <kmansley@solarflare.com>
Use a mutex for netback accelerators.
diff -r c61274a0a11c drivers/xen/netback/accel.c
--- a/drivers/xen/netback/accel.c Mon Nov 05 13:02:31 2007 +0000
+++ b/drivers/xen/netback/accel.c Mon Nov 05 13:48:06 2007 +0000
@@ -33,6 +33,7 @@
#include <linux/list.h>
#include <asm/atomic.h>
#include <xen/xenbus.h>
+#include <linux/mutex.h>
#include "common.h"
@@ -48,7 +49,7 @@
*/
static struct list_head accelerators_list;
/* Lock used to protect access to accelerators_list */
-static spinlock_t accelerators_lock;
+DEFINE_MUTEX(accelerators_mutex);
/*
* Compare a backend to an accelerator, and decide if they are
@@ -107,7 +108,7 @@ int netback_connect_accelerator(unsigned
struct netback_accel_hooks *hooks)
{
struct netback_accelerator *new_accelerator;
- unsigned eth_name_len, flags;
+ unsigned eth_name_len;
if (version != NETBACK_ACCEL_VERSION) {
if (version > NETBACK_ACCEL_VERSION) {
@@ -149,9 +150,9 @@ int netback_connect_accelerator(unsigned
atomic_set(&new_accelerator->use_count, 0);
- spin_lock_irqsave(&accelerators_lock, flags);
+ mutex_lock(&accelerators_mutex);
list_add(&new_accelerator->link, &accelerators_list);
- spin_unlock_irqrestore(&accelerators_lock, flags);
+ mutex_unlock(&accelerators_mutex);
/* tell existing backends about new plugin */
xenbus_for_each_backend(new_accelerator,
@@ -195,12 +196,12 @@ void netback_disconnect_accelerator(int
struct netback_accelerator *accelerator, *next;
unsigned flags;
- spin_lock_irqsave(&accelerators_lock, flags);
+ mutex_lock(&accelerators_mutex);
list_for_each_entry_safe(accelerator, next, &accelerators_list, link) {
if (strcmp(eth_name, accelerator->eth_name)) {
BUG_ON(atomic_read(&accelerator->use_count) != 0);
list_del(&accelerator->link);
- spin_unlock_irqrestore(&accelerators_lock, flags);
+ mutex_unlock(&accelerators_mutex);
xenbus_for_each_backend(accelerator,
netback_accelerator_cleanup_backend);
@@ -210,7 +211,7 @@ void netback_disconnect_accelerator(int
return;
}
}
- spin_unlock_irqrestore(&accelerators_lock, flags);
+ mutex_unlock(&accelerators_mutex);
}
EXPORT_SYMBOL_GPL(netback_disconnect_accelerator);
@@ -219,13 +220,12 @@ void netback_probe_accelerators(struct b
struct xenbus_device *dev)
{
struct netback_accelerator *accelerator;
- unsigned flags;
/*
* Check list of accelerators to see if any is suitable, and
* use it if it is.
*/
- spin_lock_irqsave(&accelerators_lock, flags);
+ mutex_lock(&accelerators_mutex);
list_for_each_entry(accelerator, &accelerators_list, link) {
if (match_accelerator(dev, be, accelerator) &&
try_module_get(accelerator->hooks->owner)) {
@@ -235,7 +235,7 @@ void netback_probe_accelerators(struct b
break;
}
}
- spin_unlock_irqrestore(&accelerators_lock, flags);
+ mutex_unlock(&accelerators_mutex);
}
@@ -255,5 +255,4 @@ void netif_accel_init(void)
void netif_accel_init(void)
{
INIT_LIST_HEAD(&accelerators_list);
- spin_lock_init(&accelerators_lock);
-}
+}
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