1 files changed, 84 insertions, 0 deletions

diff --git a/kernel/task_work.c b/kernel/task_work.c
new file mode 100644
index 000000000000..82d1c794066d
--- /dev/null
+++ b/kernel/task_work.c
@@ -0,0 +1,84 @@
+#include <linux/spinlock.h>
+#include <linux/task_work.h>
+#include <linux/tracehook.h>
+
+int
+task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
+{
+        unsigned long flags;
+        int err = -ESRCH;
+
+#ifndef TIF_NOTIFY_RESUME
+        if (notify)
+                return -ENOTSUPP;
+#endif
+        /*
+         * We must not insert the new work if the task has already passed
+         * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
+         * and check PF_EXITING under pi_lock.
+         */
+        raw_spin_lock_irqsave(&task->pi_lock, flags);
+        if (likely(!(task->flags & PF_EXITING))) {
+                hlist_add_head(&twork->hlist, &task->task_works);
+                err = 0;
+        }
+        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+        /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
+        if (likely(!err) && notify)
+                set_notify_resume(task);
+        return err;
+}
+
+struct task_work *
+task_work_cancel(struct task_struct *task, task_work_func_t func)
+{
+        unsigned long flags;
+        struct task_work *twork;
+        struct hlist_node *pos;
+
+        raw_spin_lock_irqsave(&task->pi_lock, flags);
+        hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
+                if (twork->func == func) {
+                        hlist_del(&twork->hlist);
+                        goto found;
+                }
+        }
+        twork = NULL;
+ found:
+        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+        return twork;
+}
+
+void task_work_run(void)
+{
+        struct task_struct *task = current;
+        struct hlist_head task_works;
+        struct hlist_node *pos;
+
+        raw_spin_lock_irq(&task->pi_lock);
+        hlist_move_list(&task->task_works, &task_works);
+        raw_spin_unlock_irq(&task->pi_lock);
+
+        if (unlikely(hlist_empty(&task_works)))
+                return;
+        /*
+         * We use hlist to save the space in task_struct, but we want fifo.
+         * Find the last entry, the list should be short, then process them
+         * in reverse order.
+         */
+        for (pos = task_works.first; pos->next; pos = pos->next)
+                ;
+
+        for (;;) {
+                struct hlist_node **pprev = pos->pprev;
+                struct task_work *twork = container_of(pos, struct task_work,
+                                                        hlist);
+                twork->func(twork);
+
+                if (pprev == &task_works.first)
+                        break;
+                pos = container_of(pprev, struct hlist_node, next);
+        }
+}