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: 561fb04 ("io_uring: replace workqueue usage with io-wq") Cc: [email protected] Signed-off-by: Pavel Begunkov <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
sirdarckcat · Sep 7, 2023 · 45500dc · 45500dc
1 parent 76d3cce
commit 45500dc
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diff --git 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
@@ -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
@@ -1975,6 +1975,8 @@ void io_wq_submit_work(struct io_wq_work *work)
 		if (!needs_poll) {
 			if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
 				break;
+			if (io_wq_worker_stopped())
+				break;
 			cond_resched();
 			continue;
 		}