[PATCH 5.8 02/70] io_uring: dont run task work on an exiting task

Greg Kroah-Hartman
2020-10-31T11:50:55Z

From: Jens Axboe <axboe@kernel.dk>

commit 6200b0ae4ea28a4bfd8eb434e33e6201b7a6a282 upstream.

This isn't safe, and isn't needed either. We are guaranteed that any
work we queue is on a live task (and will be run), or it goes to
our backup io-wq threads if the task is exiting.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/io_uring.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1762,6 +1762,12 @@ static int io_put_kbuf(struct io_kiocb *

static inline bool io_run_task_work(void)
{
+ /*
+ * Not safe to run on exiting task, and the task_work handling will
+ * not add work to such a task.
+ */
+ if (unlikely(current->flags & PF_EXITING))
+ return false;
if (current->task_works) {
__set_current_state(TASK_RUNNING);
task_work_run();
@@ -7791,6 +7797,8 @@ static void io_uring_cancel_files(struct
io_put_req(cancel_req);
}

+ /* cancellations _may_ trigger task work */
+ io_run_task_work();
schedule();
finish_wait(&ctx->inflight_wait, &wait);
}