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-rw-r--r--kernel/task_work.c22
1 files changed, 16 insertions, 6 deletions
diff --git a/kernel/task_work.c b/kernel/task_work.c
index f13ec0bda1d5..65bd3c92d6f3 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -2,16 +2,17 @@
#include <linux/task_work.h>
#include <linux/tracehook.h>
+static struct callback_head work_exited; /* all we need is ->next == NULL */
+
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
{
struct callback_head *head;
- /*
- * Not inserting the new work if the task has already passed
- * exit_task_work() is the responisbility of callers.
- */
+
do {
head = ACCESS_ONCE(task->task_works);
+ if (unlikely(head == &work_exited))
+ return -ESRCH;
work->next = head;
} while (cmpxchg(&task->task_works, head, work) != head);
@@ -30,7 +31,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
* If cmpxchg() fails we continue without updating pprev.
* Either we raced with task_work_add() which added the
* new entry before this work, we will find it again. Or
- * we raced with task_work_run(), *pprev == NULL.
+ * we raced with task_work_run(), *pprev == NULL/exited.
*/
raw_spin_lock_irqsave(&task->pi_lock, flags);
while ((work = ACCESS_ONCE(*pprev))) {
@@ -51,7 +52,16 @@ void task_work_run(void)
struct callback_head *work, *head, *next;
for (;;) {
- work = xchg(&task->task_works, NULL);
+ /*
+ * 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)
break;
/*