1 2 #include <linux/user-return-notifier.h> 3 #include <linux/percpu.h> 4 #include <linux/sched.h> 5 #include <linux/export.h> 6 7 static DEFINE_PER_CPU(struct hlist_head, return_notifier_list); 8 9 /* 10 * Request a notification when the current cpu returns to userspace. Must be 11 * called in atomic context. The notifier will also be called in atomic 12 * context. 13 */ 14 void user_return_notifier_register(struct user_return_notifier *urn) 15 { 16 set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY); 17 hlist_add_head(&urn->link, this_cpu_ptr(&return_notifier_list)); 18 } 19 EXPORT_SYMBOL_GPL(user_return_notifier_register); 20 21 /* 22 * Removes a registered user return notifier. Must be called from atomic 23 * context, and from the same cpu registration occurred in. 24 */ 25 void user_return_notifier_unregister(struct user_return_notifier *urn) 26 { 27 hlist_del(&urn->link); 28 if (hlist_empty(this_cpu_ptr(&return_notifier_list))) 29 clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY); 30 } 31 EXPORT_SYMBOL_GPL(user_return_notifier_unregister); 32 33 /* Calls registered user return notifiers */ 34 void fire_user_return_notifiers(void) 35 { 36 struct user_return_notifier *urn; 37 struct hlist_node *tmp2; 38 struct hlist_head *head; 39 40 head = &get_cpu_var(return_notifier_list); 41 hlist_for_each_entry_safe(urn, tmp2, head, link) 42 urn->on_user_return(urn); 43 put_cpu_var(return_notifier_list); 44 } 45