Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / kernel / user-return-notifier.c

diff --git a/kernel/kernel/user-return-notifier.c b/kernel/kernel/user-return-notifier.c
new file mode 100644 (file)
index 0000000..9586b67
--- /dev/null
+++ b/kernel/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/export.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, this_cpu_ptr(&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 occurred in.
+ */
+void user_return_notifier_unregister(struct user_return_notifier *urn)
+{
+       hlist_del(&urn->link);
+       if (hlist_empty(this_cpu_ptr(&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 *tmp2;
+       struct hlist_head *head;
+
+       head = &get_cpu_var(return_notifier_list);
+       hlist_for_each_entry_safe(urn, tmp2, head, link)
+               urn->on_user_return(urn);
+       put_cpu_var(return_notifier_list);
+}