We only require cmpxchg()&retry when task is exiting.
xchg() is enough in other cases like original code in ac3d0da8.
So we try our best to use xchg() and avoid competition&latency
from task_work_add().
Also remove the inner loop
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 65bd3c9..82a42e7 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -56,14 +56,13 @@ void task_work_run(void)
* work->func() can do task_work_add(), do not set
* work_exited unless the list is empty.
*/
- do {
- work = ACCESS_ONCE(task->task_works);
- head = !work && (task->flags & PF_EXITING) ?
- &work_exited : NULL;
- } while (cmpxchg(&task->task_works, work, head) != work);
-
- if (!work)
+ if (!ACCESS_ONCE(task->task_works) ||
+ !(work = xchg(&task->task_works, NULL))) {
+ if ((task->flags & PF_EXITING) &&
+ cmpxchg(&task->task_works, NULL, &work_exited))
+ continue;
break;
+ }
/*
* Synchronize with task_work_cancel(). It can't remove
* the first entry == work, cmpxchg(task_works) should
--
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