Hi，
Would you please give me some of your views on this issue? Any suggestion is
appreciative.
Thanks!
Weng Meiling
On 2014/10/15 14:42, Weng Meiling wrote:
> When the last child kobject was deleted, it's parent kobject will be deleted,
> when removing the parent kobject if the parent kobject's sd has been set NULL
> and still not been removed from it's kset's list, at the same time another one
> trigger an device adding event, the function get_parent_device() will get the
> parent object from the kset's list for kobject_add(), but this time parent
> kobject's sd has been NULL. This race will make the sysfs_create_dir() return
> ENOENT, the new kobject will be failed to added into sysfs and trigger BUG()
> when creating attribute group under the new device's directory. So move the
> kobject removal from kset's list before kobj->sd=NULL.
>
> The race situation:
>
> path0(remove parent kobj, e.g:/sys/devices/virtual/block/) path1(register a
> new device)
>
> kobject_del(){
> get_device_parent(){
> ... ...
> sysfs_remove_dir(kobj); //kobj->sd=NULL
> spin_lock(&dev->class->p->glue_dirs.list_lock);
> ... <===
> list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
> kobj_kset_leave(kobj); //remove kobj from kset list ...
> } }
>
>
> We had triggered the bug, the detail message link:
> https://lkml.org/lkml/2014/10/13/40
>
> Signed-off-by: Weng Meiling <wengmeiling.w...@huawei.com>
> ---
> lib/kobject.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/kobject.c b/lib/kobject.c
> index 58751bb..af2b7bb 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -560,12 +560,13 @@ void kobject_del(struct kobject *kobj)
> if (!kobj)
> return;
>
> + kobj_kset_leave(kobj);
> +
> sd = kobj->sd;
> sysfs_remove_dir(kobj);
> sysfs_put(sd);
>
> kobj->state_in_sysfs = 0;
> - kobj_kset_leave(kobj);
> kobject_put(kobj->parent);
> kobj->parent = NULL;
> }
>
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