Maybe "fix glue dir race condition by not removing them" is a better
title?
On Thu, Nov 06, 2014 at 04:16:38PM +0800, Yijing Wang wrote:
> There is a race condition when removing glue directory.
> It can be reproduced in following test:
>
> path 1: Add first child device
> device_add()
> get_device_parent()
> /*find parent from glue_dirs.list*/
> list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
> if (k->parent == parent_kobj) {
> kobj = kobject_get(k);
> break;
> }
> ....
> class_dir_create_and_add()
>
> path2: Remove last child device under glue dir
> device_del()
> cleanup_device_parent()
> cleanup_glue_dir()
> kobject_put(glue_dir);
>
> If path2 has been called cleanup_glue_dir(), but not
> call kobject_put(glue_dir), the glue dir is still
> in parent's kset list. Meanwhile, path1 find the glue
> dir from the glue_dirs.list. Path2 may release glue dir
> before path1 call kobject_get(). So kernel will report
> the warning and bug_on.
>
> This fix keep glue dir around once it created suggested
> by Tejun Heo.
I think you prolly want to explain why this is okay / desired.
e.g. list how the glue dir is used and how many of them are there and
explain that there's no real benefit in removing them.
...
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Signed-off-by: Weng Meiling <wengmeiling.weng@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> #3.4+
Except for the above nits.
Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
--
tejun
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