1 #include <linux/spinlock.h> 2 #include <linux/task_work.h> 3 #include <linux/tracehook.h> 4 5 int 6 task_work_add(struct task_struct *task, struct task_work *twork, bool notify) 7 { 8 unsigned long flags; 9 int err = -ESRCH; 10 11 #ifndef TIF_NOTIFY_RESUME 12 if (notify) 13 return -ENOTSUPP; 14 #endif 15 /* 16 * We must not insert the new work if the task has already passed 17 * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait() 18 * and check PF_EXITING under pi_lock. 19 */ 20 raw_spin_lock_irqsave(&task->pi_lock, flags); 21 if (likely(!(task->flags & PF_EXITING))) { 22 hlist_add_head(&twork->hlist, &task->task_works); 23 err = 0; 24 } 25 raw_spin_unlock_irqrestore(&task->pi_lock, flags); 26 27 /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */ 28 if (likely(!err) && notify) 29 set_notify_resume(task); 30 return err; 31 } 32 33 struct task_work * 34 task_work_cancel(struct task_struct *task, task_work_func_t func) 35 { 36 unsigned long flags; 37 struct task_work *twork; 38 struct hlist_node *pos; 39 40 raw_spin_lock_irqsave(&task->pi_lock, flags); 41 hlist_for_each_entry(twork, pos, &task->task_works, hlist) { 42 if (twork->func == func) { 43 hlist_del(&twork->hlist); 44 goto found; 45 } 46 } 47 twork = NULL; 48 found: 49 raw_spin_unlock_irqrestore(&task->pi_lock, flags); 50 51 return twork; 52 } 53 54 void task_work_run(void) 55 { 56 struct task_struct *task = current; 57 struct hlist_head task_works; 58 struct hlist_node *pos; 59 60 raw_spin_lock_irq(&task->pi_lock); 61 hlist_move_list(&task->task_works, &task_works); 62 raw_spin_unlock_irq(&task->pi_lock); 63 64 if (unlikely(hlist_empty(&task_works))) 65 return; 66 /* 67 * We use hlist to save the space in task_struct, but we want fifo. 68 * Find the last entry, the list should be short, then process them 69 * in reverse order. 70 */ 71 for (pos = task_works.first; pos->next; pos = pos->next) 72 ; 73 74 for (;;) { 75 struct hlist_node **pprev = pos->pprev; 76 struct task_work *twork = container_of(pos, struct task_work, 77 hlist); 78 twork->func(twork); 79 80 if (pprev == &task_works.first) 81 break; 82 pos = container_of(pprev, struct hlist_node, next); 83 } 84 } 85