1 files changed, 80 insertions, 0 deletions
diff --git a/kernel/task_work.c b/kernel/task_work.c
new file mode 100644
index 00000000000..91d4e1742a0
--- /dev/null
+++ b/kernel/task_work.c
@@ -0,0 +1,80 @@
+#include <linux/spinlock.h>
+#include <linux/task_work.h>
+#include <linux/tracehook.h>
+
+int
+task_work_add(struct task_struct *task, struct callback_head *twork, bool notify)
+{
+	struct callback_head *last, *first;
+	unsigned long flags;
+
+	/*
+	 * Not inserting the new work if the task has already passed
+	 * exit_task_work() is the responisbility of callers.
+	 */
+	raw_spin_lock_irqsave(&task->pi_lock, flags);
+	last = task->task_works;
+	first = last ? last->next : twork;
+	twork->next = first;
+	if (last)
+		last->next = twork;
+	task->task_works = twork;
+	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+	/* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
+	if (notify)
+		set_notify_resume(task);
+	return 0;
+}
+
+struct callback_head *
+task_work_cancel(struct task_struct *task, task_work_func_t func)
+{
+	unsigned long flags;
+	struct callback_head *last, *res = NULL;
+
+	raw_spin_lock_irqsave(&task->pi_lock, flags);
+	last = task->task_works;
+	if (last) {
+		struct callback_head *q = last, *p = q->next;
+		while (1) {
+			if (p->func == func) {
+				q->next = p->next;
+				if (p == last)
+					task->task_works = q == p ? NULL : q;
+				res = p;
+				break;
+			}
+			if (p == last)
+				break;
+			q = p;
+			p = q->next;
+		}
+	}
+	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+	return res;
+}
+
+void task_work_run(void)
+{
+	struct task_struct *task = current;
+	struct callback_head *p, *q;
+
+	while (1) {
+		raw_spin_lock_irq(&task->pi_lock);
+		p = task->task_works;
+		task->task_works = NULL;
+		raw_spin_unlock_irq(&task->pi_lock);
+
+		if (unlikely(!p))
+			return;
+
+		q = p->next; /* head */
+		p->next = NULL; /* cut it */
+		while (q) {
+			p = q->next;
+			q->func(q);
+			q = p;
+		}
+	}
+}