kobject: introduce kobj_completion

A common way to handle kobject lifetimes in embedded in objects with different lifetime rules is to pair the kobject with a struct completion. This introduces a kobj_completion structure that can be used in place of the pairing, along with several convenience functions for initialization, release, and put-and-wait. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kobject: introduce kobj_completion
A common way to handle kobject lifetimes in embedded in objects with different lifetime rules is to pair the kobject with a struct completion. This introduces a kobj_completion structure that can be used in place of the pairing, along with several convenience functions for initialization, release, and put-and-wait. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Jeff Mahoney · Greg Kroah-Hartman
1 parent 1296fc02c2
Showing 2 changed files with 68 additions and 0 deletions Side-by-side Diff
include/linux/kobj_completion.h
lib/kobject.c
+#ifndef _KOBJ_COMPLETION_H_
+#define _KOBJ_COMPLETION_H_
+
+#include <linux/kobject.h>
+#include <linux/completion.h>
+
+struct kobj_completion {
+	struct kobject kc_kobj;
+	struct completion kc_unregister;
+};
+
+#define kobj_to_kobj_completion(kobj) \
+	container_of(kobj, struct kobj_completion, kc_kobj)
+
+void kobj_completion_init(struct kobj_completion *kc, struct kobj_type *ktype);
+void kobj_completion_release(struct kobject *kobj);
+void kobj_completion_del_and_wait(struct kobj_completion *kc);
+#endif /* _KOBJ_COMPLETION_H_ */
@@ -13,6 +13,7 @@
  */
  
 #include <linux/kobject.h>
+#include <linux/kobj_completion.h>
 #include <linux/string.h>
 #include <linux/export.h>
 #include <linux/stat.h>
@@ -748,6 +749,55 @@
 	.show	= kobj_attr_show,
 	.store	= kobj_attr_store,
 };
+
+/**
+ * kobj_completion_init - initialize a kobj_completion object.
+ * @kc: kobj_completion
+ * @ktype: type of kobject to initialize
+ *
+ * kobj_completion structures can be embedded within structures with different
+ * lifetime rules.  During the release of the enclosing object, we can
+ * wait on the release of the kobject so that we don't free it while it's
+ * still busy.
+ */
+void kobj_completion_init(struct kobj_completion *kc, struct kobj_type *ktype)
+{
+	init_completion(&kc->kc_unregister);
+	kobject_init(&kc->kc_kobj, ktype);
+}
+EXPORT_SYMBOL_GPL(kobj_completion_init);
+
+/**
+ * kobj_completion_release - release a kobj_completion object
+ * @kobj: kobject embedded in kobj_completion
+ *
+ * Used with kobject_release to notify waiters that the kobject has been
+ * released.
+ */
+void kobj_completion_release(struct kobject *kobj)
+{
+	struct kobj_completion *kc = kobj_to_kobj_completion(kobj);
+	complete(&kc->kc_unregister);
+}
+EXPORT_SYMBOL_GPL(kobj_completion_release);
+
+/**
+ * kobj_completion_del_and_wait - release the kobject and wait for it
+ * @kc: kobj_completion object to release
+ *
+ * Delete the kobject from sysfs and drop the reference count.  Then wait
+ * until any other outstanding references are also dropped.  This routine
+ * is only necessary once other references may have been taken on the
+ * kobject.  Typically this happens when the kobject has been published
+ * to sysfs via kobject_add.
+ */
+void kobj_completion_del_and_wait(struct kobj_completion *kc)
+{
+	kobject_del(&kc->kc_kobj);
+	kobject_put(&kc->kc_kobj);
+	wait_for_completion(&kc->kc_unregister);
+}
+EXPORT_SYMBOL_GPL(kobj_completion_del_and_wait);
  
 /**
  * kset_register - initialize and add a kset.
	1	+#ifndef _KOBJ_COMPLETION_H_
	2	+#define _KOBJ_COMPLETION_H_
	3	+
	4	+#include <linux/kobject.h>
	5	+#include <linux/completion.h>
	6	+
	7	+struct kobj_completion {
	8	+ struct kobject kc_kobj;
	9	+ struct completion kc_unregister;
	10	+};
	11	+
	12	+#define kobj_to_kobj_completion(kobj) \
	13	+ container_of(kobj, struct kobj_completion, kc_kobj)
	14	+
	15	+void kobj_completion_init(struct kobj_completion kc, struct kobj_type ktype);
	16	+void kobj_completion_release(struct kobject *kobj);
	17	+void kobj_completion_del_and_wait(struct kobj_completion *kc);
	18	+#endif /* _KOBJ_COMPLETION_H_ */
...	...	@@ -13,6 +13,7 @@
13	13	*/
14	14
15	15	#include <linux/kobject.h>
	16	+#include <linux/kobj_completion.h>
16	17	#include <linux/string.h>
17	18	#include <linux/export.h>
18	19	#include <linux/stat.h>
...	...	@@ -748,6 +749,55 @@
748	749	.show = kobj_attr_show,
749	750	.store = kobj_attr_store,
750	751	};
	752	+
	753	+/**
	754	+ * kobj_completion_init - initialize a kobj_completion object.
	755	+ * @kc: kobj_completion
	756	+ * @ktype: type of kobject to initialize
	757	+ *
	758	+ * kobj_completion structures can be embedded within structures with different
	759	+ * lifetime rules. During the release of the enclosing object, we can
	760	+ * wait on the release of the kobject so that we don't free it while it's
	761	+ * still busy.
	762	+ */
	763	+void kobj_completion_init(struct kobj_completion kc, struct kobj_type ktype)
	764	+{
	765	+ init_completion(&kc->kc_unregister);
	766	+ kobject_init(&kc->kc_kobj, ktype);
	767	+}
	768	+EXPORT_SYMBOL_GPL(kobj_completion_init);
	769	+
	770	+/**
	771	+ * kobj_completion_release - release a kobj_completion object
	772	+ * @kobj: kobject embedded in kobj_completion
	773	+ *
	774	+ * Used with kobject_release to notify waiters that the kobject has been
	775	+ * released.
	776	+ */
	777	+void kobj_completion_release(struct kobject *kobj)
	778	+{
	779	+ struct kobj_completion *kc = kobj_to_kobj_completion(kobj);
	780	+ complete(&kc->kc_unregister);
	781	+}
	782	+EXPORT_SYMBOL_GPL(kobj_completion_release);
	783	+
	784	+/**
	785	+ * kobj_completion_del_and_wait - release the kobject and wait for it
	786	+ * @kc: kobj_completion object to release
	787	+ *
	788	+ * Delete the kobject from sysfs and drop the reference count. Then wait
	789	+ * until any other outstanding references are also dropped. This routine
	790	+ * is only necessary once other references may have been taken on the
	791	+ * kobject. Typically this happens when the kobject has been published
	792	+ * to sysfs via kobject_add.
	793	+ */
	794	+void kobj_completion_del_and_wait(struct kobj_completion *kc)
	795	+{
	796	+ kobject_del(&kc->kc_kobj);
	797	+ kobject_put(&kc->kc_kobj);
	798	+ wait_for_completion(&kc->kc_unregister);
	799	+}
	800	+EXPORT_SYMBOL_GPL(kobj_completion_del_and_wait);
751	801
752	802	/**
753	803	* kset_register - initialize and add a kset.