[greatbridf]

Summary

Testcase /mnt/pthread_test hangs after the threads are joined (issue #61): the process reaches the end of the test but never exits, freezing forever in the clear-tid futex wait.

Root cause: futex_exit() in src/kernel/task/futex.rs called do_futex_exit(thread) without awaiting the returned future:

let _ = do_futex_exit(thread);

Because let _ = <future> merely drops the future, do_futex_exit() was never executed at all. As a result the thread was never detached from its futex state and the clear-tid futex wakeups were never performed, so the joiner kept waiting forever.

Fix

One-line fix: actually await the future so do_futex_exit() runs.

 pub async fn futex_exit(thread: &Thread) {
     // We don't care about any error happened inside.
     // If they've set up a wrong pointer, good luck to them...
-    let _ = do_futex_exit(thread);
+    let _ = do_futex_exit(thread).await;
 }

Fixes a regression from b6d54d6 ("mm, proc: add an exited thread reaper").

Verification

Reproduced and verified with make run MODE=release, running /mnt/pthread_test in the guest:

• Before: the test hangs forever after pthread_join.
• After: the test prints Final counter value: 20000 and the process exits normally.

Fixes #61