io_uring: use io-wq manager as backup task if task is exiting
If the original task is (or has) exited, then the task work will not get
queued properly. Allow for using the io-wq manager task to queue this
work for execution, and ensure that the io-wq manager notices and runs
this work if woken up (or exiting).
Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b343525..2460c33 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4120,6 +4120,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
__poll_t mask, task_work_func_t func)
{
struct task_struct *tsk;
+ int ret;
/* for instances that support it check for an event match first: */
if (mask && !(mask & poll->events))
@@ -4133,11 +4134,15 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
req->result = mask;
init_task_work(&req->task_work, func);
/*
- * If this fails, then the task is exiting. If that is the case, then
- * the exit check will ultimately cancel these work items. Hence we
- * don't need to check here and handle it specifically.
+ * If this fails, then the task is exiting. Punt to one of the io-wq
+ * threads to ensure the work gets run, we can't always rely on exit
+ * cancelation taking care of this.
*/
- task_work_add(tsk, &req->task_work, true);
+ ret = task_work_add(tsk, &req->task_work, true);
+ if (unlikely(ret)) {
+ tsk = io_wq_get_task(req->ctx->io_wq);
+ task_work_add(tsk, &req->task_work, true);
+ }
wake_up_process(tsk);
return 1;
}