io_uring: Disable multi_thread_submit_and_complete

This CL reverts previous attempts at reducing the flakiness of the test
and disables it completely.

BUG=b:183722981
TEST=./test_all

Change-Id: I36527d6404c67ff9e73792676a52f064d2f48d14
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2787246
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

io_uring/src/uring.rs

@@ -1423,7 +1423,9 @@ mod tests {
         );
     }
 
+    // TODO(b/183722981): Fix and re-enable test
     #[test]
+    #[ignore]
     fn multi_thread_submit_and_complete() {
         const NUM_SUBMITTERS: usize = 7;
         const NUM_COMPLETERS: usize = 3;
@@ -1504,13 +1506,30 @@ mod tests {
             t.join().unwrap();
         }
 
-        // Make sure we didn't submit more entries than expected.
-        assert_eq!(uring.complete_ring.num_ready(), 0);
+        // Now that all submitters are finished, add NOPs to wake up any completers blocked on the
+        // syscall.
+        for i in 0..NUM_COMPLETERS {
+            uring
+                .add_nop((NUM_SUBMITTERS * ITERATIONS + i) as UserData)
+                .unwrap();
+        }
+        uring.submit().unwrap();
+
+        for t in threads {
+            t.join().unwrap();
+        }
+
+        // Make sure we didn't submit more entries than expected. Only the last few NOPs added to
+        // wake up the completer threads may still be in the completion ring.
+        assert!(uring.complete_ring.num_ready() <= NUM_COMPLETERS as u32);
         assert_eq!(
             in_flight.lock().abs() as u32 + uring.complete_ring.num_ready(),
-            0
+            NUM_COMPLETERS as u32
+        );
+        assert_eq!(uring.submit_ring.lock().added, 0);
+        assert_eq!(
+            uring.stats.total_ops.load(Ordering::Relaxed),
+            (NUM_SUBMITTERS * ITERATIONS + NUM_COMPLETERS) as u64
         );
-
-        // Leave the completer threads hanging to be cleaned up by the OS.
     }
 }