Apply cosmetic changes to unified scheduler (#1861)

* Apply cosmetic changes to unified scheduler

* Use first instead of old-fashioned firstly

Co-authored-by: Andrew Fitzgerald <apfitzge@gmail.com>

---------

Co-authored-by: Andrew Fitzgerald <apfitzge@gmail.com>

runtime/src/installed_scheduler_pool.rs

@@ -25,15 +25,16 @@ use {
     log::*,
     solana_program_runtime::timings::ExecuteTimings,
     solana_sdk::{
+        clock::Slot,
         hash::Hash,
-        slot_history::Slot,
         transaction::{Result, SanitizedTransaction, TransactionError},
     },
     std::{
         fmt::{self, Debug},
         mem,
         ops::Deref,
         sync::{Arc, RwLock},
+        thread,
     },
 };
 #[cfg(feature = "dev-context-only-utils")]
@@ -623,7 +624,7 @@ impl BankWithSchedulerInner {
             "wait_for_scheduler_termination(slot: {}, reason: {:?}): started at {:?}...",
             bank.slot(),
             reason,
-            std::thread::current(),
+            thread::current(),
         );
 
         let mut scheduler = scheduler.write().unwrap();
@@ -656,7 +657,7 @@ impl BankWithSchedulerInner {
             reason,
             was_noop,
             result_with_timings.as_ref().map(|(result, _)| result),
-            std::thread::current(),
+            thread::current(),
         );
         trace!(
             "wait_for_scheduler_termination(result_with_timings: {:?})",
@@ -667,7 +668,7 @@ impl BankWithSchedulerInner {
     }
 
     fn drop_scheduler(&self) {
-        if std::thread::panicking() {
+        if thread::panicking() {
             error!(
                 "BankWithSchedulerInner::drop_scheduler(): slot: {} skipping due to already panicking...",
                 self.bank.slot(),

unified-scheduler-pool/src/lib.rs

@@ -940,7 +940,7 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
         // 4. the handler thread processes the dispatched task.
         // 5. the handler thread reply back to the scheduler thread as an executed task.
         // 6. the scheduler thread post-processes the executed task.
-        let scheduler_main_loop = || {
+        let scheduler_main_loop = {
             let handler_count = self.pool.handler_count;
             let session_result_sender = self.session_result_sender.clone();
             // Taking new_task_receiver here is important to ensure there's a single receiver. In
@@ -1006,7 +1006,7 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
                 };
 
                 // The following loop maintains and updates ResultWithTimings as its
-                // externally-provieded mutable state for each session in this way:
+                // externally-provided mutable state for each session in this way:
                 //
                 // 1. Initial result_with_timing is propagated implicitly by the moved variable.
                 // 2. Subsequent result_with_timings are propagated explicitly from
@@ -1062,9 +1062,8 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
                                     Ok(NewTaskPayload::CloseSubchannel) => {
                                         session_ending = true;
                                     }
-                                    Ok(NewTaskPayload::OpenSubchannel(_context_and_result_with_timings)) => {
-                                        unreachable!();
-                                    }
+                                    Ok(NewTaskPayload::OpenSubchannel(_context_and_result_with_timings)) =>
+                                        unreachable!(),
                                     Err(RecvError) => {
                                         // Mostly likely is that this scheduler is dropped for pruned blocks of
                                         // abandoned forks...
@@ -1087,17 +1086,16 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
                         is_finished = session_ending && state_machine.has_no_active_task();
                     }
 
-                    if session_ending {
-                        state_machine.reinitialize();
-                        session_result_sender
-                            .send(std::mem::replace(
-                                &mut result_with_timings,
-                                initialized_result_with_timings(),
-                            ))
-                            .expect("always outlived receiver");
-                        session_ending = false;
-                    }
+                    // Finalize the current session after asserting it's explicitly requested so.
+                    assert!(session_ending);
+                    // Send result first because this is blocking the replay code-path.
+                    session_result_sender
+                        .send(result_with_timings)
+                        .expect("always outlived receiver");
+                    state_machine.reinitialize();
+                    session_ending = false;
 
+                    // Prepare for the new session.
                     match new_task_receiver.recv() {
                         Ok(NewTaskPayload::OpenSubchannel((
                             new_context,
@@ -1111,13 +1109,13 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
                                 .unwrap();
                             result_with_timings = new_result_with_timings;
                         }
-                        Ok(_) => {
-                            unreachable!();
-                        }
                         Err(_) => {
-                            // This unusual condition must be triggered by ThreadManager::drop();
+                            // This unusual condition must be triggered by ThreadManager::drop().
+                            // Initialize result_with_timings with a harmless value...
+                            result_with_timings = initialized_result_with_timings();
                             break 'nonaborted_main_loop;
                         }
+                        Ok(_) => unreachable!(),
                     }
                 }
 
@@ -1212,7 +1210,7 @@ impl<S: SpawnableScheduler<TH>, TH: TaskHandler> ThreadManager<S, TH> {
         self.scheduler_thread = Some(
             thread::Builder::new()
                 .name("solScheduler".to_owned())
-                .spawn_tracked(scheduler_main_loop())
+                .spawn_tracked(scheduler_main_loop)
                 .unwrap(),
         );