Hey.
I think reverted a similar patch when moving past 2.6.18 a while ago,
but I don't remember the first kernel versions affected right now.
On Wed, 2010-01-20 at 06:45 -0500, Joe Jin wrote:
> static void connect(struct backend_info *);
> static int connect_ring(struct backend_info *);
> @@ -122,10 +123,19 @@
> struct device_attribute *attr, \
> char *buf) \
> { \
> - struct xenbus_device *dev = to_xenbus_device(_dev); \
> - struct backend_info *be = dev->dev.driver_data; \
> + ssize_t ret = -ENODEV; \
> + struct xenbus_device *dev; \
> + struct backend_info *be; \
\
> - return sprintf(buf, format, ##args); \
> + if (!get_device(_dev)) \
> + return ret; \
> + dev = to_xenbus_device(_dev); \
I think this deadlocks here:
> + read_lock(&sysfs_read_lock); \
> + if ((be = dev->dev.driver_data) != NULL) \
> + ret = sprintf(buf, format, ##args); \
> + read_unlock(&sysfs_read_lock); \
> + put_device(_dev); \
> + return ret; \
> } \
> static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
>
> @@ -170,6 +180,7 @@
> {
> struct backend_info *be = dev->dev.driver_data;
>
> + write_lock(&sysfs_read_lock);
> if (be->group_added)
.. and here:
> xentap_sysfs_delif(be->dev);
> if (be->backend_watch.node) {
> @@ -187,6 +198,7 @@
> }
> kfree(be);
> dev->dev.driver_data = NULL;
> + write_unlock(&sysfs_read_lock);
> return 0;
> }
Sysfs may refcount these nodes, blocking xentap_sysfs_delif().
Daniel
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