t/io_uring: SQPOLL fixes

Use the proper primitives to load/store the ring head/tail. And as
importantly, account any submit as a full submit, even if we don't
need to call io_uring_enter().

This fixes hangs with using SQPOLL.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/t/io_uring.c b/t/io_uring.c
index 044f9195679566f802460672a3b9c6d96f33be07..ff4c7a7c01807ed46bd73dca4da85de0e606158d 100644 (file)
--- a/t/io_uring.c
+++ b/t/io_uring.c
@@ -233,8 +233,7 @@ static int prep_more_ios(struct submitter *s, int max_ios)
        next_tail = tail = *ring->tail;
        do {
                next_tail++;
-               read_barrier();
-               if (next_tail == *ring->head)
+               if (next_tail == atomic_load_acquire(ring->head))
                        break;
 
                index = tail & sq_ring_mask;
@@ -244,10 +243,8 @@ static int prep_more_ios(struct submitter *s, int max_ios)
                tail = next_tail;
        } while (prepped < max_ios);
 
-       if (*ring->tail != tail) {
-               *ring->tail = tail;
-               write_barrier();
-       }
+       if (prepped)
+               atomic_store_release(ring->tail, tail);
        return prepped;
 }
 
@@ -284,7 +281,7 @@ static int reap_events(struct submitter *s)
                struct file *f;
 
                read_barrier();
-               if (head == *ring->tail)
+               if (head == atomic_load_acquire(ring->tail))
                        break;
                cqe = &ring->cqes[head & cq_ring_mask];
                if (!do_nop) {
@@ -301,9 +298,10 @@ static int reap_events(struct submitter *s)
                head++;
        } while (1);
 
-       s->inflight -= reaped;
-       *ring->head = head;
-       write_barrier();
+       if (reaped) {
+               s->inflight -= reaped;
+               atomic_store_release(ring->head, head);
+       }
        return reaped;
 }
 
@@ -320,6 +318,7 @@ static void *submitter_fn(void *data)
        prepped = 0;
        do {
                int to_wait, to_submit, this_reap, to_prep;
+               unsigned ring_flags = 0;
 
                if (!prepped && s->inflight < depth) {
                        to_prep = min(depth - s->inflight, batch_submit);
@@ -338,15 +337,20 @@ submit:
                 * Only need to call io_uring_enter if we're not using SQ thread
                 * poll, or if IORING_SQ_NEED_WAKEUP is set.
                 */
-               if (!sq_thread_poll || (*ring->flags & IORING_SQ_NEED_WAKEUP)) {
+               if (sq_thread_poll)
+                       ring_flags = atomic_load_acquire(ring->flags);
+               if (!sq_thread_poll || ring_flags & IORING_SQ_NEED_WAKEUP) {
                        unsigned flags = 0;
 
                        if (to_wait)
                                flags = IORING_ENTER_GETEVENTS;
-                       if ((*ring->flags & IORING_SQ_NEED_WAKEUP))
+                       if (ring_flags & IORING_SQ_NEED_WAKEUP)
                                flags |= IORING_ENTER_SQ_WAKEUP;
                        ret = io_uring_enter(s, to_submit, to_wait, flags);
                        s->calls++;
+               } else {
+                       /* for SQPOLL, we submitted it all effectively */
+                       ret = to_submit;
                }
 
                /*