rt: Remove `threaded_scheduler()` and `basic_scheduler()` (#2876)

Co-authored-by: Alice Ryhl <alice@ryhl.io>
Co-authored-by: Carl Lerche <me@carllerche.com>

90 files changed, 1469 insertions, 1687 deletions

diff --git a/benches/mpsc.rs b/benches/mpsc.rs
index 2f3fe963..3f7e3fca 100644
--- a/benches/mpsc.rs
+++ b/benches/mpsc.rs
@@ -4,6 +4,13 @@ use tokio::sync::mpsc;
 type Medium = [usize; 64];
 type Large = [Medium; 64];
 
+fn rt() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
+        .build()
+        .unwrap()
+}
+
 fn create_1_medium(b: &mut Bencher) {
     b.iter(|| {
         black_box(&mpsc::channel::<Medium>(1));
@@ -43,11 +50,7 @@ fn send_large(b: &mut Bencher) {
 }
 
 fn contention_bounded(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let rt = rt();
 
     b.iter(|| {
         rt.block_on(async move {
@@ -70,11 +73,7 @@ fn contention_bounded(b: &mut Bencher) {
 }
 
 fn contention_bounded_full(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let rt = rt();
 
     b.iter(|| {
         rt.block_on(async move {
@@ -97,11 +96,7 @@ fn contention_bounded_full(b: &mut Bencher) {
 }
 
 fn contention_unbounded(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let rt = rt();
 
     b.iter(|| {
         rt.block_on(async move {
@@ -124,11 +119,7 @@ fn contention_unbounded(b: &mut Bencher) {
 }
 
 fn uncontented_bounded(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let rt = rt();
 
     b.iter(|| {
         rt.block_on(async move {
@@ -146,11 +137,7 @@ fn uncontented_bounded(b: &mut Bencher) {
 }
 
 fn uncontented_unbounded(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let rt = rt();
 
     b.iter(|| {
         rt.block_on(async move {
diff --git a/benches/scheduler.rs b/benches/scheduler.rs
index 801de72a..68a6d6a4 100644
--- a/benches/scheduler.rs
+++ b/benches/scheduler.rs
@@ -139,9 +139,8 @@ fn chained_spawn(b: &mut Bencher) {
 }
 
 fn rt() -> Runtime {
-    runtime::Builder::new()
-        .threaded_scheduler()
-        .core_threads(4)
+    runtime::Builder::new_multi_thread()
+        .worker_threads(4)
         .enable_all()
         .build()
         .unwrap()
diff --git a/benches/signal.rs b/benches/signal.rs
index 3a354c6b..fcad40da 100644
--- a/benches/signal.rs
+++ b/benches/signal.rs
@@ -45,9 +45,9 @@ fn many_signals(bench: &mut Bencher) {
     let num_signals = 10;
     let (tx, mut rx) = mpsc::channel(num_signals);
 
-    let rt = runtime::Builder::new()
+    let rt = runtime::Builder::new_multi_thread()
         // Intentionally single threaded to measure delays in propagating wakes
-        .basic_scheduler()
+        .worker_threads(0)
         .enable_all()
         .build()
         .unwrap();
diff --git a/benches/spawn.rs b/benches/spawn.rs
index f76daf3f..72a40357 100644
--- a/benches/spawn.rs
+++ b/benches/spawn.rs
@@ -10,8 +10,7 @@ async fn work() -> usize {
 }
 
 fn basic_scheduler_local_spawn(bench: &mut Bencher) {
-    let runtime = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let runtime = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
     runtime.block_on(async {
@@ -23,8 +22,7 @@ fn basic_scheduler_local_spawn(bench: &mut Bencher) {
 }
 
 fn threaded_scheduler_local_spawn(bench: &mut Bencher) {
-    let runtime = tokio::runtime::Builder::new()
-        .threaded_scheduler()
+    let runtime = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
     runtime.block_on(async {
@@ -36,8 +34,7 @@ fn threaded_scheduler_local_spawn(bench: &mut Bencher) {
 }
 
 fn basic_scheduler_remote_spawn(bench: &mut Bencher) {
-    let runtime = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let runtime = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
 
@@ -48,10 +45,7 @@ fn basic_scheduler_remote_spawn(bench: &mut Bencher) {
 }
 
 fn threaded_scheduler_remote_spawn(bench: &mut Bencher) {
-    let runtime = tokio::runtime::Builder::new()
-        .threaded_scheduler()
-        .build()
-        .unwrap();
+    let runtime = tokio::runtime::Builder::new_multi_thread().build().unwrap();
 
     bench.iter(|| {
         let h = runtime.spawn(work());
diff --git a/benches/sync_rwlock.rs b/benches/sync_rwlock.rs
index 30c66e49..46eeac0c 100644
--- a/benches/sync_rwlock.rs
+++ b/benches/sync_rwlock.rs
@@ -3,9 +3,8 @@ use std::sync::Arc;
 use tokio::{sync::RwLock, task};
 
 fn read_uncontended(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -22,9 +21,8 @@ fn read_uncontended(b: &mut Bencher) {
 }
 
 fn read_concurrent_uncontended_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -51,8 +49,7 @@ fn read_concurrent_uncontended_multi(b: &mut Bencher) {
 }
 
 fn read_concurrent_uncontended(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let rt = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
 
@@ -78,9 +75,8 @@ fn read_concurrent_uncontended(b: &mut Bencher) {
 }
 
 fn read_concurrent_contended_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -108,8 +104,7 @@ fn read_concurrent_contended_multi(b: &mut Bencher) {
 }
 
 fn read_concurrent_contended(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let rt = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
 
diff --git a/benches/sync_semaphore.rs b/benches/sync_semaphore.rs
index 32d4aa2b..19a1dd33 100644
--- a/benches/sync_semaphore.rs
+++ b/benches/sync_semaphore.rs
@@ -3,9 +3,8 @@ use std::sync::Arc;
 use tokio::{sync::Semaphore, task};
 
 fn uncontended(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -27,9 +26,8 @@ async fn task(s: Arc<Semaphore>) {
 }
 
 fn uncontended_concurrent_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -51,8 +49,8 @@ fn uncontended_concurrent_multi(b: &mut Bencher) {
 }
 
 fn uncontended_concurrent_single(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(0)
         .build()
         .unwrap();
 
@@ -73,9 +71,8 @@ fn uncontended_concurrent_single(b: &mut Bencher) {
 }
 
 fn contended_concurrent_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .core_threads(6)
-        .threaded_scheduler()
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
         .build()
         .unwrap();
 
@@ -97,8 +94,7 @@ fn contended_concurrent_multi(b: &mut Bencher) {
 }
 
 fn contended_concurrent_single(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new()
-        .basic_scheduler()
+    let rt = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
 
diff --git a/tests-build/Cargo.toml b/tests-build/Cargo.toml
index 68231d71..e76621b4 100644
--- a/tests-build/Cargo.toml
+++ b/tests-build/Cargo.toml
@@ -7,6 +7,7 @@ publish = false
 
 [features]
 full = ["tokio/full"]
+rt-core = ["tokio/rt-core", "tokio/macros"]
 
 [dependencies]
 tokio = { path = "../tokio", optional = true }
diff --git a/tests-build/tests/fail/macros_core_no_default.rs b/tests-build/tests/fail/macros_core_no_default.rs
new file mode 100644
index 00000000..23f8847d
--- /dev/null
+++ b/tests-build/tests/fail/macros_core_no_default.rs
@@ -0,0 +1,6 @@
+use tests_build::tokio;
+
+#[tokio::main]
+async fn my_fn() {}
+
+fn main() {}
diff --git a/tests-build/tests/fail/macros_core_no_default.stderr b/tests-build/tests/fail/macros_core_no_default.stderr
new file mode 100644
index 00000000..a3ae32cd
--- /dev/null
+++ b/tests-build/tests/fail/macros_core_no_default.stderr
@@ -0,0 +1,7 @@
+error: The default runtime flavor is `multi_thread`, but the `rt-threaded` feature is disabled.
+ --> $DIR/macros_core_no_default.rs:3:1
+  |
+3 | #[tokio::main]
+  | ^^^^^^^^^^^^^^
+  |
+  = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/tests-build/tests/fail/macros_invalid_input.stderr b/tests-build/tests/fail/macros_invalid_input.stderr
index 96fdcb17..4c68bd93 100644
--- a/tests-build/tests/fail/macros_invalid_input.stderr
+++ b/tests-build/tests/fail/macros_invalid_input.stderr
@@ -4,7 +4,7 @@ error: the async keyword is missing from the function declaration
 4 | fn main_is_not_async() {}
   | ^^
 
-error: Unknown attribute foo is specified; expected `basic_scheduler` or `threaded_scheduler`
+error: Unknown attribute foo is specified; expected one of: `flavor`, `worker_threads`
  --> $DIR/macros_invalid_input.rs:6:15
   |
 6 | #[tokio::main(foo)]
@@ -28,7 +28,7 @@ error: the test function cannot accept arguments
 16 | async fn test_fn_has_args(_x: u8) {}
    |                           ^^^^^^
 
-error: Unknown attribute foo is specified; expected `basic_scheduler` or `threaded_scheduler`
+error: Unknown attribute foo is specified; expected one of: `flavor`, `worker_threads`
   --> $DIR/macros_invalid_input.rs:18:15
    |
 18 | #[tokio::test(foo)]
diff --git a/tests-build/tests/macros.rs b/tests-build/tests/macros.rs
index 170db227..a12a20ef 100644
--- a/tests-build/tests/macros.rs
+++ b/tests-build/tests/macros.rs
@@ -1,9 +1,12 @@
 #[test]
-fn compile_fail() {
+fn compile_fail_full() {
     let t = trybuild::TestCases::new();