relibc: P5-robust-mutex-enotrec-fix — apply Phase 0e patch

src/pthread/mod.rs

@@ -43,9 +43,13 @@ pub unsafe fn init() {
         thread.stack_size = STACK_SIZE;
     }
 
-    unsafe { Tcb::current() }
-        .expect_notls("no TCB present for main thread")
-        .pthread = thread;
+    let tcb = unsafe { Tcb::current() }
+        .expect_notls("no TCB present for main thread");
+    tcb.pthread = thread;
+
+    OS_TID_TO_PTHREAD
+        .lock()
+        .insert(Sys::current_os_tid(), ForceSendSync(tcb as *const Tcb as *mut Tcb));
 }
 
 //static NEXT_INDEX: AtomicU32 = AtomicU32::new(FIRST_THREAD_IDX + 1);

src/sync/pthread_mutex.rs

@@ -136,11 +136,7 @@ impl RlctMutex {
                 Err(thread) => {
                     let owner = thread & INDEX_MASK;
 
-                    if !crate::pthread::mutex_owner_id_is_live(owner) {
-                        if !self.robust {
-                            return Err(Errno(ENOTRECOVERABLE));
-                        }
-
+                    if !crate::pthread::mutex_owner_id_is_live(owner) && self.robust {
                         let new_value = (thread & WAITING_BIT) | FUTEX_OWNER_DIED | this_thread;
                         match self.inner.compare_exchange(
                             thread,
@@ -151,6 +147,11 @@ impl RlctMutex {
                             Ok(_) => return self.finish_lock_acquire(true),
                             Err(_) => continue,
                         }
+                    } else if !crate::pthread::mutex_owner_id_is_live(owner) {
+                        // Non-robust mutex with apparently-dead owner: per POSIX the
+                        // behaviour is undefined.  We conservatively keep spinning /
+                        // futex-waiting rather than returning ENOTRECOVERABLE, which
+                        // would crash any Rust std::sync::Mutex user.
                     }
 
                     if spins_left > 0 {