From 3f1628c4ff3f2608091483bb13dd8f22502a5121 Mon Sep 17 00:00:00 2001
From: Liu Jiang <gerry@linux.alibaba.com>
Date: Wed, 1 Dec 2021 18:04:36 +0800
Subject: [PATCH] Fix a bug in SubmissionQueue::sync()

The uring driver may update queue.head, so SubmissionQueue::sync()
should read queue.head instead of queue.tail.

Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>
---
 io-uring-test/src/tests/queue.rs | 8 ++++++++
 src/squeue.rs                    | 1 +
 2 files changed, 9 insertions(+)

diff --git a/io-uring-test/src/tests/queue.rs b/io-uring-test/src/tests/queue.rs
index 5a37ff86..758df697 100644
--- a/io-uring-test/src/tests/queue.rs
+++ b/io-uring-test/src/tests/queue.rs
@@ -12,7 +12,9 @@ pub fn test_nop(ring: &mut IoUring, test: &Test) -> anyhow::Result<()> {
 
     unsafe {
         let mut queue = ring.submission();
+        assert_eq!(queue.len(), 0);
         queue.push(&nop_e).expect("queue is full");
+        assert_eq!(queue.len(), 1);
     }
 
     ring.submit_and_wait(1)?;
@@ -23,6 +25,12 @@ pub fn test_nop(ring: &mut IoUring, test: &Test) -> anyhow::Result<()> {
     assert_eq!(cqes[0].user_data(), 0x42);
     assert_eq!(cqes[0].result(), 0);
 
+    unsafe {
+        let mut queue = ring.submission();
+        queue.sync();
+        assert_eq!(queue.len(), 0);
+    }
+
     Ok(())
 }
 
diff --git a/src/squeue.rs b/src/squeue.rs
index 0b6edb64..d88feb3d 100644
--- a/src/squeue.rs
+++ b/src/squeue.rs
@@ -178,6 +178,7 @@ impl SubmissionQueue<'_> {
         unsafe {
             (*self.queue.tail).store(self.tail, atomic::Ordering::Release);
             self.tail = (*self.queue.tail).load(atomic::Ordering::Acquire);
+            //self.head = (*self.queue.head).load(atomic::Ordering::Acquire);
         }
     }