io_uring: break out of iowq iopoll on teardown

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>

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index 62f3455..1ecc8c7 100644 (file)
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -174,6 +174,16 @@ static void io_worker_ref_put(struct io_wq *wq)
                complete(&wq->worker_done);
 }
 
+bool io_wq_worker_stopped(void)
+{
+       struct io_worker *worker = current->worker_private;
+
+       if (WARN_ON_ONCE(!io_wq_current_is_worker()))
+               return true;
+
+       return test_bit(IO_WQ_BIT_EXIT, &worker->wq->state);
+}
+
 static void io_worker_cancel_cb(struct io_worker *worker)
 {
        struct io_wq_acct *acct = io_wq_get_acct(worker);

diff --git a/io_uring/io-wq.h b/io_uring/io-wq.h
index 06d9ca9..2b2a640 100644 (file)
--- a/io_uring/io-wq.h
+++ b/io_uring/io-wq.h
@@ -52,6 +52,7 @@ void io_wq_hash_work(struct io_wq_work *work, void *val);
 
 int io_wq_cpu_affinity(struct io_uring_task *tctx, 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)
 {

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 0f0ba31..58d8dd3 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1975,6 +1975,8 @@ fail:
                if (!needs_poll) {
                        if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
                                break;
+                       if (io_wq_worker_stopped())
+                               break;
                        cond_resched();
                        continue;
                }