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SubjectRe: [PATCH 2/2] kobject: send KOBJ_REMOVE uevent when the object is removed from sysfs
On Wed, May 27, 2020 at 11:01:16AM +0200, Rafael J. Wysocki wrote:
>
> So Guenter, can you please test the patch below to see if it still introduces
> the problems seen by you on ARM?
>

arm64 and arm64be boot tests pass with the patch below. Some arm boot
tests fail, but I think that is due to some other problem with -next.
Hard to say for sure at this point because -next is pretty badly broken
overall. I'll need to run some bisects to see what is going on.

Guenter

> ---
> From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Subject: [PATCH] kobject: Make sure the parent does not get released before its children
>
> In the function kobject_cleanup(), kobject_del(kobj) is
> called before the kobj->release(). That makes it possible to
> release the parent of the kobject before the kobject itself.
>
> To fix that, adding function __kboject_del() that does
> everything that kobject_del() does except release the parent
> reference. kobject_cleanup() then calls __kobject_del()
> instead of kobject_del(), and separately decrements the
> reference count of the parent kobject after kobj->release()
> has been called.
>
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Reported-by: kernel test robot <rong.a.chen@intel.com>
> Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"")
> Suggested-by: "Rafael J. Wysocki" <rafael@kernel.org>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> [ rjw: Drop parent reference only when called __kobject_del() ]
> Signed-off-by: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> ---
> lib/kobject.c | 34 +++++++++++++++++++++++-----------
> 1 file changed, 23 insertions(+), 11 deletions(-)
>
> Index: linux-pm/lib/kobject.c
> ===================================================================
> --- linux-pm.orig/lib/kobject.c
> +++ linux-pm/lib/kobject.c
> @@ -599,14 +599,7 @@ out:
> }
> EXPORT_SYMBOL_GPL(kobject_move);
>
> -/**
> - * kobject_del() - Unlink kobject from hierarchy.
> - * @kobj: object.
> - *
> - * This is the function that should be called to delete an object
> - * successfully added via kobject_add().
> - */
> -void kobject_del(struct kobject *kobj)
> +static void __kobject_del(struct kobject *kobj)
> {
> struct kernfs_node *sd;
> const struct kobj_type *ktype;
> @@ -625,9 +618,23 @@ void kobject_del(struct kobject *kobj)
>
> kobj->state_in_sysfs = 0;
> kobj_kset_leave(kobj);
> - kobject_put(kobj->parent);
> kobj->parent = NULL;
> }
> +
> +/**
> + * kobject_del() - Unlink kobject from hierarchy.
> + * @kobj: object.
> + *
> + * This is the function that should be called to delete an object
> + * successfully added via kobject_add().
> + */
> +void kobject_del(struct kobject *kobj)
> +{
> + struct kobject *parent = kobj->parent;
> +
> + __kobject_del(kobj);
> + kobject_put(parent);
> +}
> EXPORT_SYMBOL(kobject_del);
>
> /**
> @@ -663,7 +670,9 @@ EXPORT_SYMBOL(kobject_get_unless_zero);
> */
> static void kobject_cleanup(struct kobject *kobj)
> {
> + struct kobject *parent = kobj->parent;
> struct kobj_type *t = get_ktype(kobj);
> + bool state_in_sysfs = kobj->state_in_sysfs;
> const char *name = kobj->name;
>
> pr_debug("kobject: '%s' (%p): %s, parent %p\n",
> @@ -681,10 +690,10 @@ static void kobject_cleanup(struct kobje
> }
>
> /* remove from sysfs if the caller did not do it */
> - if (kobj->state_in_sysfs) {
> + if (state_in_sysfs) {
> pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",
> kobject_name(kobj), kobj);
> - kobject_del(kobj);
> + __kobject_del(kobj);
> }
>
> if (t && t->release) {
> @@ -698,6 +707,9 @@ static void kobject_cleanup(struct kobje
> pr_debug("kobject: '%s': free name\n", name);
> kfree_const(name);
> }
> +
> + if (state_in_sysfs)
> + kobject_put(parent);
> }
>
> #ifdef CONFIG_DEBUG_KOBJECT_RELEASE
>
>
>

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