aboutsummaryrefslogtreecommitdiff
path: root/kernel/user-return-notifier.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/user-return-notifier.c')
-rw-r--r--kernel/user-return-notifier.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/kernel/user-return-notifier.c b/kernel/user-return-notifier.c
new file mode 100644
index 00000000000..eb27fd3430a
--- /dev/null
+++ b/kernel/user-return-notifier.c
@@ -0,0 +1,44 @@
+
+#include <linux/user-return-notifier.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+
+static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
+
+/*
+ * Request a notification when the current cpu returns to userspace. Must be
+ * called in atomic context. The notifier will also be called in atomic
+ * context.
+ */
+void user_return_notifier_register(struct user_return_notifier *urn)
+{
+ set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+ hlist_add_head(&urn->link, &__get_cpu_var(return_notifier_list));
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_register);
+
+/*
+ * Removes a registered user return notifier. Must be called from atomic
+ * context, and from the same cpu registration occured in.
+ */
+void user_return_notifier_unregister(struct user_return_notifier *urn)
+{
+ hlist_del(&urn->link);
+ if (hlist_empty(&__get_cpu_var(return_notifier_list)))
+ clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
+
+/* Calls registered user return notifiers */
+void fire_user_return_notifiers(void)
+{
+ struct user_return_notifier *urn;
+ struct hlist_node *tmp1, *tmp2;
+ struct hlist_head *head;
+
+ head = &get_cpu_var(return_notifier_list);
+ hlist_for_each_entry_safe(urn, tmp1, tmp2, head, link)
+ urn->on_user_return(urn);
+ put_cpu_var(return_notifier_list);
+}