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-rw-r--r--include/linux/cgroup.h20
1 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed2573e149fa..710a005c6b7a 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -344,6 +344,26 @@ static inline bool css_tryget_online(struct cgroup_subsys_state *css)
}
/**
+ * css_is_dying - test whether the specified css is dying
+ * @css: target css
+ *
+ * Test whether @css is in the process of offlining or already offline. In
+ * most cases, ->css_online() and ->css_offline() callbacks should be
+ * enough; however, the actual offline operations are RCU delayed and this
+ * test returns %true also when @css is scheduled to be offlined.
+ *
+ * This is useful, for example, when the use case requires synchronous
+ * behavior with respect to cgroup removal. cgroup removal schedules css
+ * offlining but the css can seem alive while the operation is being
+ * delayed. If the delay affects user visible semantics, this test can be
+ * used to resolve the situation.
+ */
+static inline bool css_is_dying(struct cgroup_subsys_state *css)
+{
+ return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt);
+}
+
+/**
* css_put - put a css reference
* @css: target css
*