[PATCH 5.10 315/406] io_uring: break out of iowq iopoll on teardown

Greg Kroah-Hartman
2023-09-17T19:38:05Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ upstream commit 45500dc4e01c167ee063f3dcc22f51ced5b2b1e9 ]

io-wq will retry iopoll even when it failed with -EAGAIN. If that
races with task exit, which sets TIF_NOTIFY_SIGNAL for all its workers,
such workers might potentially infinitely spin retrying iopoll again and
again and each time failing on some allocation / waiting / etc. Don't
keep spinning if io-wq is dying.

Fixes: 561fb04a6a225 ("io_uring: replace workqueue usage with io-wq")
Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/io-wq.c | 10 ++++++++++
io_uring/io-wq.h | 1 +
io_uring/io_uring.c | 3 ++-
3 files changed, 13 insertions(+), 1 deletion(-)

--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -176,6 +176,16 @@ static void io_worker_ref_put(struct io_
complete(&wq->worker_done);
}

+bool io_wq_worker_stopped(void)
+{
+ struct io_worker *worker = current->pf_io_worker;
+
+ if (WARN_ON_ONCE(!io_wq_current_is_worker()))
+ return true;
+
+ return test_bit(IO_WQ_BIT_EXIT, &worker->wqe->wq->state);
+}
+
static void io_worker_cancel_cb(struct io_worker *worker)
{
struct io_wqe_acct *acct = io_wqe_get_acct(worker);
--- a/io_uring/io-wq.h
+++ b/io_uring/io-wq.h
@@ -129,6 +129,7 @@ void io_wq_hash_work(struct io_wq_work *

int io_wq_cpu_affinity(struct io_wq *wq, cpumask_var_t mask);
int io_wq_max_workers(struct io_wq *wq, int *new_count);
+bool io_wq_worker_stopped(void);

static inline bool io_wq_is_hashed(struct io_wq_work *work)
{
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -6898,7 +6898,8 @@ static void io_wq_submit_work(struct io_
*/
if (ret != -EAGAIN || !(req->ctx->flags & IORING_SETUP_IOPOLL))
break;
-
+ if (io_wq_worker_stopped())
+ break;
/*
* If REQ_F_NOWAIT is set, then don't wait or retry with
* poll. -EAGAIN is final for that case.