logger: refactor usage of sync primitives

use `std::sync::Barrier` instead of the barebones `Condvar` + `Mutex`
combo

src/commands/mod.rs

@@ -4,11 +4,7 @@ mod compress;
 mod decompress;
 mod list;
 
-use std::{
-    ops::ControlFlow,
-    path::PathBuf,
-    sync::{Arc, Condvar, Mutex},
-};
+use std::{ops::ControlFlow, path::PathBuf};
 
 use rayon::prelude::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator};
 use utils::colors;
@@ -22,7 +18,7 @@ use crate::{
     list::ListOptions,
     utils::{
         self,
-        logger::{info_accessible, setup_channel, spawn_logger_thread, warning},
+        logger::{info_accessible, spawn_logger_thread, warning},
         to_utf, EscapedPathDisplay, FileVisibilityPolicy,
     },
     CliArgs, QuestionPolicy,
@@ -57,20 +53,9 @@ pub fn run(
     question_policy: QuestionPolicy,
     file_visibility_policy: FileVisibilityPolicy,
 ) -> crate::Result<()> {
-    let (log_receiver, dropper) = setup_channel();
-
-    let synchronization_pair = Arc::new((Mutex::new(false), Condvar::new()));
-    spawn_logger_thread(log_receiver, synchronization_pair.clone());
+    let handler = spawn_logger_thread();
     run_cmd(args, question_policy, file_visibility_policy)?;
-
-    // Send a message for the logger thread to shut down.
-    // This is needed, otherwise the logging thread will never exit.
-    drop(dropper);
-
-    // Hold the main thread from exiting until the background thread signals its shutdown.
-    let (lock, cvar) = &*synchronization_pair;
-    let guard = lock.lock().unwrap();
-    let _flushed = cvar.wait(guard).unwrap();
+    handler.shutdown_and_wait();
 
     Ok(())
 }

src/utils/logger.rs

@@ -1,6 +1,6 @@
-use std::sync::{mpsc, Arc, Condvar, Mutex, OnceLock};
+use std::sync::{mpsc, OnceLock};
 
-pub use logger_thread::{setup_channel, spawn_logger_thread};
+pub use logger_thread::spawn_logger_thread;
 
 use super::colors::{ORANGE, RESET, YELLOW};
 use crate::accessible::is_running_in_accessible_mode;
@@ -49,7 +49,7 @@ pub fn warning(contents: String) {
 /// Message object used for sending logs from worker threads to a logging thread via channels.
 /// See <https://github.com/ouch-org/ouch/issues/643>
 #[derive(Debug)]
-pub struct PrintMessage {
+struct PrintMessage {
     contents: String,
     accessible: bool,
     level: MessageLevel,
@@ -89,6 +89,8 @@ enum MessageLevel {
 }
 
 mod logger_thread {
+    use std::sync::{Arc, Barrier};
+
     use super::*;
 
     type LogReceiver = mpsc::Receiver<Option<PrintMessage>>;
@@ -97,10 +99,10 @@ mod logger_thread {
     static SENDER: OnceLock<LogSender> = OnceLock::new();
 
     #[track_caller]
-    pub fn setup_channel() -> (LogReceiver, LoggerDropper) {
+    fn setup_channel() -> LogReceiver {
         let (tx, rx) = mpsc::channel();
         SENDER.set(tx).expect("`setup_channel` should only be called once");
-        (rx, LoggerDropper)
+        rx
     }
 
     #[track_caller]
@@ -108,44 +110,8 @@ mod logger_thread {
         SENDER.get().expect("No sender, you need to call `setup_channel` first")
     }
 
-    pub fn spawn_logger_thread(log_receiver: LogReceiver, synchronization_pair: Arc<(Mutex<bool>, Condvar)>) {
-        rayon::spawn(move || {
-            const BUFFER_CAPACITY: usize = 10;
-            let mut buffer = Vec::<String>::with_capacity(BUFFER_CAPACITY);
-
-            loop {
-                let msg = log_receiver.recv().expect("Failed to receive log message");
-
-                let is_shutdown_message = msg.is_none();
-
-                // Append message to buffer
-                if let Some(msg) = msg.as_ref().and_then(PrintMessage::to_processed_message) {
-                    buffer.push(msg);
-                }
-
-                let should_flush = buffer.len() == BUFFER_CAPACITY || is_shutdown_message;
-
-                if should_flush {
-                    let text = buffer.join("\n");
-                    eprintln!("{text}");
-                    buffer.clear();
-                }
-
-                if is_shutdown_message {
-                    break;
-                }
-            }
-
-            // Wake up the main thread
-            let (lock, cvar) = &*synchronization_pair;
-            let mut flushed = lock.lock().unwrap();
-            *flushed = true;
-            cvar.notify_one();
-        });
-    }
-
     #[track_caller]
-    pub fn send_log_message(msg: PrintMessage) {
+    pub(super) fn send_log_message(msg: PrintMessage) {
         send_message(Some(msg));
     }
 
@@ -154,11 +120,61 @@ mod logger_thread {
         get_sender().send(msg).expect("Failed to send internal message");
     }
 
-    pub struct LoggerDropper;
+    pub struct LoggerThreadHandle {
+        shutdown_barrier: Arc<Barrier>,
+    }
 
-    impl Drop for LoggerDropper {
-        fn drop(&mut self) {
+    impl LoggerThreadHandle {
+        /// Tell logger to shutdown and waits till it does.
+        pub fn shutdown_and_wait(self) {
+            // Signal the shutdown
             send_message(None);
+            // Wait for confirmation
+            self.shutdown_barrier.wait();
         }
     }
+
+    pub fn spawn_logger_thread() -> LoggerThreadHandle {
+        let log_receiver = setup_channel();
+
+        let shutdown_barrier = Arc::new(Barrier::new(2));
+
+        let handle = LoggerThreadHandle {
+            shutdown_barrier: shutdown_barrier.clone(),
+        };
+
+        rayon::spawn(move || run_logger(log_receiver, shutdown_barrier));
+
+        handle
+    }
+
+    fn run_logger(log_receiver: LogReceiver, shutdown_barrier: Arc<Barrier>) {
+        const BUFFER_CAPACITY: usize = 10;
+        let mut buffer = Vec::<String>::with_capacity(BUFFER_CAPACITY);
+
+        loop {
+            let msg = log_receiver.recv().expect("Failed to receive log message");
+
+            let is_shutdown_message = msg.is_none();
+
+            // Append message to buffer
+            if let Some(msg) = msg.as_ref().and_then(PrintMessage::to_processed_message) {
+                buffer.push(msg);
+            }
+
+            let should_flush = buffer.len() == BUFFER_CAPACITY || is_shutdown_message;
+
+            if should_flush {
+                let text = buffer.join("\n");
+                eprintln!("{text}");
+                buffer.clear();
+            }
+
+            if is_shutdown_message {
+                break;
+            }
+        }
+
+        shutdown_barrier.wait();
+    }
 }