From 1f604e7eac3018785c98429139ed10281b2a7f35 Mon Sep 17 00:00:00 2001
From: Alan Somers <asomers@gmail.com>
Date: Fri, 3 Jun 2022 19:51:51 -0600
Subject: [PATCH] Only use one thread with Tokio

When Tokio gets event notification from kevent, the pending future may
belong to a different thread.  If so, it signals the other thread and
pends on kevent again.  But the other thread may not have had time to
call aio_return yet.  In that case, the first thread's kevent will
immediately return again.

The correct solution is to set EV_ONESHOT on the aiocb.  But Rust's libc
doesn't currently expose the necessary field.  Until it does, restrict
Tokio to just a single thread.

https://github.com/rust-lang/libc/pull/2813
---
 bfffs-fio/src/lib.rs         | 2 +-
 bfffs/benches/fs_destroy.rs  | 2 +-
 bfffs/src/bin/bfffsd/main.rs | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/bfffs-fio/src/lib.rs b/bfffs-fio/src/lib.rs
index a37d9d2e..32d7e500 100644
--- a/bfffs-fio/src/lib.rs
+++ b/bfffs-fio/src/lib.rs
@@ -166,7 +166,7 @@ pub extern "C" fn rust_ctor() {
 
 lazy_static! {
     static ref RUNTIME: RwLock<Runtime> = RwLock::new(
-        Builder::new_multi_thread()
+        Builder::new_current_thread()
             .enable_time()
             .enable_io()
             .build()
diff --git a/bfffs/benches/fs_destroy.rs b/bfffs/benches/fs_destroy.rs
index 6f37064f..b5e2b2ca 100644
--- a/bfffs/benches/fs_destroy.rs
+++ b/bfffs/benches/fs_destroy.rs
@@ -316,7 +316,7 @@ fn fs_destroy(
     Ok(())
 }
 
-#[tokio::main]
+#[tokio::main(flavor = "current_thread")]
 async fn main() -> Result<()> {
     tracing_subscriber::fmt()
         .pretty()
diff --git a/bfffs/src/bin/bfffsd/main.rs b/bfffs/src/bin/bfffsd/main.rs
index 5d1f5f2b..08fa2edf 100644
--- a/bfffs/src/bin/bfffsd/main.rs
+++ b/bfffs/src/bin/bfffsd/main.rs
@@ -353,7 +353,7 @@ impl Bfffsd {
     }
 }
 
-#[tokio::main]
+#[tokio::main(flavor = "current_thread")]
 async fn main() {
     tracing_subscriber::fmt()
         .pretty()