fix: repeat submit on iopoll without sqpoll

tokio-rs#297
Fixes: tokio-rs#296

src/runtime/driver/handle.rs

@@ -34,10 +34,32 @@ pub(crate) struct WeakHandle {
     inner: Weak<RefCell<Driver>>,
 }
 
+struct ThreadParker;
+impl std::future::Future for ThreadParker {
+    type Output = ();
+    fn poll(
+        self: std::pin::Pin<&mut Self>,
+        ctx: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<<Self as std::future::Future>::Output> {
+        ctx.waker().clone().wake();
+        std::task::Poll::Pending
+    }
+}
+
 impl Handle {
-    pub(crate) fn new(b: &crate::Builder) -> io::Result<Self> {
+    pub(crate) fn new(
+        b: &crate::Builder,
+        tokio_rt: &tokio::runtime::Runtime,
+        local: &tokio::task::LocalSet,
+    ) -> io::Result<Self> {
+        let driver = Driver::new(b)?;
+        let params = driver.uring.params();
+        if params.is_setup_iopoll() && !params.is_setup_sqpoll() {
+            let _guard = tokio_rt.enter();
+            local.spawn_local(ThreadParker {});
+        }
         Ok(Self {
-            inner: Rc::new(RefCell::new(Driver::new(b)?)),
+            inner: Rc::new(RefCell::new(driver)),
         })
     }
 

src/runtime/driver/mod.rs

@@ -19,7 +19,7 @@ pub(crate) struct Driver {
     ops: Ops,
 
     /// IoUring bindings
-    uring: IoUring,
+    pub(crate) uring: IoUring,
 
     /// Reference to the currently registered buffers.
     /// Ensures that the buffers are not dropped until
@@ -40,6 +40,8 @@ impl Driver {
     pub(crate) fn new(b: &crate::Builder) -> io::Result<Driver> {
         let uring = b.urb.build(b.entries)?;
 
+        if uring.params().is_setup_iopoll() && !uring.params().is_setup_sqpoll() {}
+
         Ok(Driver {
             ops: Ops::new(),
             uring,

src/runtime/mod.rs

@@ -81,7 +81,7 @@ impl Runtime {
 
         let tokio_rt = ManuallyDrop::new(rt);
         let local = ManuallyDrop::new(LocalSet::new());
-        let driver = driver::Handle::new(b)?;
+        let driver = driver::Handle::new(b, &tokio_rt, &local)?;
 
         start_uring_wakes_task(&tokio_rt, &local, driver.clone());
 

tests/fs_file.rs

@@ -315,6 +315,33 @@ fn basic_fallocate() {
     });
 }
 
+#[test]
+fn iopoll_without_sqpoll() {
+    use std::os::unix::fs::OpenOptionsExt;
+    let mut builder = tokio_uring::builder();
+    builder.uring_builder(&tokio_uring::uring_builder().setup_iopoll());
+    let runtime = tokio_uring::Runtime::new(&builder).unwrap();
+    let tmp = tempfile();
+    runtime.block_on(async {
+        let file = std::fs::OpenOptions::new()
+            .write(true)
+            .custom_flags(libc::O_DIRECT)
+            .open(tmp.path())
+            .unwrap();
+        let file = tokio_uring::fs::File::from_std(file);
+
+        let layout = std::alloc::Layout::from_size_align(512, 512).unwrap();
+        let buf = unsafe {
+            let raw = std::alloc::alloc(layout);
+            std::ptr::copy("asdf".as_ptr(), raw, 4);
+            std::slice::from_raw_parts(raw, 512)
+        };
+
+        let res = file.write_at(buf, 0).submit().await.0.unwrap();
+        assert_eq!(res, 512);
+    });
+}
+
 fn tempfile() -> NamedTempFile {
     NamedTempFile::new().unwrap()
 }