+/**
+ * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
+ * @cgrp: the cgroup to be checked for liveness
+ *
+ * Returns true (with lock held) on success, or false (with no lock
+ * held) on failure.
+ */
+int cgroup_lock_live_group(struct cgroup *cgrp)
+{
+ mutex_lock(&cgroup_mutex);
+ if (cgroup_is_removed(cgrp)) {
+ mutex_unlock(&cgroup_mutex);
+ return false;
+ }
+ return true;
+}
+
+static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
+ const char *buffer)
+{
+ BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+ if (!cgroup_lock_live_group(cgrp))
+ return -ENODEV;
+ strcpy(cgrp->root->release_agent_path, buffer);
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+}
+
+static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
+ struct seq_file *seq)
+{
+ if (!cgroup_lock_live_group(cgrp))
+ return -ENODEV;
+ seq_puts(seq, cgrp->root->release_agent_path);
+ seq_putc(seq, '\n');
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+}
+