diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 26730fcec4cec..546ac5ae296d5 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -30,6 +30,7 @@ use std::io::{self, BufReader};
 use std::path::{Path, PathBuf};
 use std::process::{Child, Command, ExitStatus, Output, Stdio};
 use std::str;
+use std::sync::{Arc, Mutex, RwLock};
 
 use glob::glob;
 use lazy_static::lazy_static;
@@ -73,6 +74,21 @@ fn disable_error_reporting<F: FnOnce() -> R, R>(f: F) -> R {
     f()
 }
 
+fn get_or_create_coverage_file(path: &Path, create: impl FnOnce() -> File) -> Arc<Mutex<File>> {
+    lazy_static::lazy_static! {
+        static ref COVERAGE_FILE_LOCKS: RwLock<HashMap<PathBuf, Arc<Mutex<File>>>> = RwLock::new(HashMap::new());
+    }
+
+    {
+        let locks = COVERAGE_FILE_LOCKS.read().unwrap();
+        locks.get(path).map(Arc::clone)
+    }
+    .unwrap_or_else(|| {
+        let mut locks = COVERAGE_FILE_LOCKS.write().unwrap();
+        locks.entry(path.to_path_buf()).or_insert_with(|| Arc::new(Mutex::new(create()))).clone()
+    })
+}
+
 /// The name of the environment variable that holds dynamic library locations.
 pub fn dylib_env_var() -> &'static str {
     if cfg!(windows) {
@@ -3237,13 +3253,20 @@ impl<'test> TestCx<'test> {
                 coverage_file_path.push("rustfix_missing_coverage.txt");
                 debug!("coverage_file_path: {}", coverage_file_path.display());
 
-                let mut file = OpenOptions::new()
-                    .create(true)
-                    .append(true)
-                    .open(coverage_file_path.as_path())
-                    .expect("could not create or open file");
+                let file_ref = get_or_create_coverage_file(&coverage_file_path, || {
+                    OpenOptions::new()
+                        .create(true)
+                        .write(true)
+                        .truncate(true)
+                        .open(coverage_file_path.as_path())
+                        .expect("could not create or open file")
+                });
+                let mut file = file_ref.lock().unwrap();
 
-                if writeln!(file, "{}", self.testpaths.file.display()).is_err() {
+                if writeln!(file, "{}", self.testpaths.file.display())
+                    .and_then(|_| file.sync_data())
+                    .is_err()
+                {
                     panic!("couldn't write to {}", coverage_file_path.display());
                 }
             }