feat: add SYS_FUTEX_WAIT and SYS_FUTEX_WAKE syscalls; revamp desktop application categories

programs/include/montauk/thread.h

@@ -148,6 +148,28 @@ namespace montauk {
         return (int)syscall0(montauk::abi::SYS_THREAD_SELF);
     }
 
+    // Block while *addr == expected. Returns 0 when woken by futex_wake,
+    // WouldBlock if *addr had already changed, TimedOut when timeout_ns
+    // elapsed (FUTEX_WAIT_FOREVER = no deadline, 0 = check only, otherwise
+    // rounded up to the 1 ms tick). Futexes are private to the process.
+    // A 0 return is never spurious, but always re-check the condition.
+    inline int futex_wait(uint32_t* addr, uint32_t expected,
+                          uint64_t timeout_ns = montauk::abi::FUTEX_WAIT_FOREVER) {
+        int64_t r = syscall3(montauk::abi::SYS_FUTEX_WAIT, (uint64_t)addr,
+                             (uint64_t)expected, timeout_ns);
+        return r < 0 ? (int)-r : 0;
+    }
+
+    // Wake up to `count` waiters on addr, longest-waiting first. Returns the
+    // number woken, or a negative status for a bad address.
+    inline int futex_wake(uint32_t* addr, uint32_t count = 1) {
+        return (int)syscall2(montauk::abi::SYS_FUTEX_WAKE, (uint64_t)addr, (uint64_t)count);
+    }
+
+    inline int futex_wake_all(uint32_t* addr) {
+        return futex_wake(addr, montauk::abi::FUTEX_WAKE_ALL);
+    }
+
     // Lightweight mutex backed by a single atomic word + the kernel
     // yield syscall. Adequate for short critical sections; a heavier
     // primitive can wrap mailbox_recv when blocking semantics are needed.