ci: fix spurious CI failure (#5752)

PR #5720 introduced runtime self-tuning. It included a test that
attempts to verify self-tuning logic. The test is heavily reliant on
timing details. This patch attempts to make the test a bit more reliable
by not assuming tuning will converge within a set amount of time.

.github/workflows/ci.yml

@@ -294,7 +294,7 @@ jobs:
           toolchain: ${{ env.rust_nightly }}
       - uses: Swatinem/rust-cache@v2
       - name: asan
-        run: cargo test --workspace --all-features --target x86_64-unknown-linux-gnu --tests -- --test-threads 1
+        run: cargo test --workspace --all-features --target x86_64-unknown-linux-gnu --tests -- --test-threads 1 --nocapture
         env:
           RUSTFLAGS: -Z sanitizer=address
           # Ignore `trybuild` errors as they are irrelevant and flaky on nightly

tokio/tests/rt_threaded.rs

@@ -627,7 +627,6 @@ fn test_tuning() {
     }
 
     // Now, hammer the injection queue until the interval drops.
-    let mut i = 0;
     let mut n = 0;
     loop {
         let curr = interval.load(Relaxed);
@@ -645,18 +644,16 @@ fn test_tuning() {
             break;
         }
 
-        let counter = counter.clone();
-        let interval = interval.clone();
+        if Arc::strong_count(&interval) < 5_000 {
+            let counter = counter.clone();
+            let interval = interval.clone();
 
-        if i <= 5_000 {
-            i += 1;
             rt.spawn(async move {
                 let prev = counter.swap(0, Relaxed);
                 interval.store(prev, Relaxed);
             });
+
             std::thread::yield_now();
-        } else {
-            std::thread::sleep(Duration::from_micros(500));
         }
     }
 
@@ -682,7 +679,6 @@ fn test_tuning() {
     }
 
     // Now, hammer the injection queue until the interval reaches the expected range.
-    let mut i = 0;
     let mut n = 0;
     loop {
         let curr = interval.load(Relaxed);
@@ -697,20 +693,17 @@ fn test_tuning() {
             break;
         }
 
-        let counter = counter.clone();
-        let interval = interval.clone();
+        if Arc::strong_count(&interval) <= 5_000 {
+            let counter = counter.clone();
+            let interval = interval.clone();
 
-        if i <= 5_000 {
-            i += 1;
             rt.spawn(async move {
                 let prev = counter.swap(0, Relaxed);
                 interval.store(prev, Relaxed);
             });
-
-            std::thread::yield_now();
-        } else {
-            std::thread::sleep(Duration::from_micros(500));
         }
+
+        std::thread::yield_now();
     }
 
     flag.store(false, Relaxed);