pgrep: retry flaky test_thread_ids

src/uu/pgrep/src/process.rs

@@ -902,15 +902,26 @@ unknown              /dev/tty        4 1-63 console"#;
     #[test]
     #[cfg(target_os = "linux")]
     fn test_thread_ids() {
-        let main_tid = rustix::thread::gettid().as_raw_nonzero().get() as u64;
+        let main_tid = rustix::thread::gettid().as_raw_nonzero().get() as usize;
         std::thread::spawn(move || {
-            let mut pid_entry = ProcessInformation::current_process_info().unwrap();
-            let thread_ids = pid_entry.thread_ids();
-
-            assert!(thread_ids.contains(&(main_tid as usize)));
-
-            let new_thread_tid = rustix::thread::gettid().as_raw_nonzero().get() as u64;
-            assert!(thread_ids.contains(&(new_thread_tid as usize)));
+            let new_thread_tid = rustix::thread::gettid().as_raw_nonzero().get() as usize;
+            // This thread is already running, but readdir on /proc/<pid>/task
+            // can skip entries while other test threads exit concurrently, so a
+            // single snapshot may miss a tid (https://github.com/uutils/procps/issues/471).
+            let deadline = std::time::Instant::now() + std::time::Duration::from_secs(2);
+            loop {
+                let mut pid_entry = ProcessInformation::current_process_info().unwrap();
+                let thread_ids = pid_entry.thread_ids();
+                if thread_ids.contains(&main_tid) && thread_ids.contains(&new_thread_tid) {
+                    return;
+                }
+                if std::time::Instant::now() >= deadline {
+                    panic!(
+                        "thread_ids missing main {main_tid} or new {new_thread_tid}: {thread_ids:?}"
+                    );
+                }
+                std::thread::sleep(std::time::Duration::from_millis(5));
+            }
         })
         .join()
         .unwrap();