On 2010-01-20 18:16, Daniel Stodden wrote:
>
> 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().
Would you like to give me some info about of blocking and deadlocks?
Checked xentap_sysfs_delif() -> sysfs_remove_group() and I did not found
blocking codes, maybe I lost something?
Thanks,
Joe
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