Ping guys ? I think this is worth fixing. Muchun Song <smuchun@xxxxxxxxx> 于2019年5月25日周六 下午8:15写道： > > Hi greg k-h, > > Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 于2019年5月25日周六 上午3:04写道： > > > > On Thu, May 16, 2019 at 10:23:42PM +0800, Muchun Song wrote: > > > There is a race condition between removing glue directory and adding a new > > > device under the glue directory. It can be reproduced in following test: > > > > <snip> > > > > Is this related to: > > Subject: [PATCH v3] drivers: core: Remove glue dirs early only when refcount is 1 > > > > ? > > > > If so, why is the solution so different? > > In the v1 patch, the solution is that remove glue dirs early only when > refcount is 1. So > the v1 patch like below: > > @@ -1825,7 +1825,7 @@ static void cleanup_glue_dir(struct device *dev, > struct kobject *glue_dir) > return; > > mutex_lock(&gdp_mutex); > - if (!kobject_has_children(glue_dir)) > + if (!kobject_has_children(glue_dir) && kref_read(&glue_dir->kref) == 1) > kobject_del(glue_dir); > kobject_put(glue_dir); > mutex_unlock(&gdp_mutex); > ----------------------------------------------------------------------- > > But from Ben's suggestion as below: > > I find relying on the object count for such decisions rather fragile as > it could be taken temporarily for other reasons, couldn't it ? In which > case we would just fail... > > Ideally, the looking up of the glue dir and creation of its child > should be protected by the same lock instance (the gdp_mutex in that > case). > ----------------------------------------------------------------------- > > So another solution is used from Ben's suggestion in the v2 patch. But > I forgot to update the commit message until the v4 patch. Thanks. > > Yours, > Muchun
