1 files changed, 45 insertions, 49 deletions

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 82d1c794066d..91d4e1742a0c 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -3,82 +3,78 @@
 #include <linux/tracehook.h>
 
 int
-task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
+task_work_add(struct task_struct *task, struct callback_head *twork, bool notify)
 {
+        struct callback_head *last, *first;
         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.
+         * 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);
-        if (likely(!(task->flags & PF_EXITING))) {
-                hlist_add_head(&twork->hlist, &task->task_works);
-                err = 0;
-        }
+        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 (likely(!err) && notify)
+        if (notify)
                 set_notify_resume(task);
-        return err;
+        return 0;
 }
 
-struct task_work *
+struct callback_head *
 task_work_cancel(struct task_struct *task, task_work_func_t func)
 {
         unsigned long flags;
-        struct task_work *twork;
-        struct hlist_node *pos;
+        struct callback_head *last, *res = NULL;
 
         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;
+        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;
                 }
         }
-        twork = NULL;
- found:
         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
-
-        return twork;
+        return res;
 }
 
 void task_work_run(void)
 {
         struct task_struct *task = current;
-        struct hlist_head task_works;
-        struct hlist_node *pos;
+        struct callback_head *p, *q;
 
-        raw_spin_lock_irq(&task->pi_lock);
-        hlist_move_list(&task->task_works, &task_works);
-        raw_spin_unlock_irq(&task->pi_lock);
+        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(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)
-                ;
+                if (unlikely(!p))
+                        return;
 
-        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);
+                q = p->next; /* head */
+                p->next = NULL; /* cut it */
+                while (q) {
+                        p = q->next;
+                        q->func(q);
+                        q = p;
+                }
         }
 }