Add test for futex syscall.

tests/run-pass/concurrency/linux-futex.rs

@@ -0,0 +1,132 @@
+// Unfortunately, the test framework does not support 'only-linux',
+// so we need to ignore Windows and macOS instead.
+// ignore-macos: Uses Linux-only APIs
+// ignore-windows: Uses Linux-only APIs
+// compile-flags: -Zmiri-disable-isolation
+
+#![feature(rustc_private)]
+extern crate libc;
+
+use std::ptr;
+use std::thread;
+use std::time::{Duration, Instant};
+
+fn wake_nobody() {
+    let mut futex = 0;
+
+    // Wake 1 waiter. Expect zero waiters woken up, as nobody is waiting.
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            &futex as *const i32,
+            libc::FUTEX_WAKE,
+            1,
+        ), 0);
+    }
+
+    // Same, but without omitting the unused arguments.
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            &futex as *const i32,
+            libc::FUTEX_WAKE,
+            1,
+            0,
+            0,
+            0,
+        ), 0);
+    }
+}
+
+fn wake_dangling() {
+    let futex = Box::new(0);
+    let ptr: *const i32 = &*futex;
+    drop(futex);
+
+    // Wake 1 waiter. Expect zero waiters woken up, as nobody is waiting.
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            ptr,
+            libc::FUTEX_WAKE,
+            1,
+        ), 0);
+    }
+}
+
+fn wait_wrong_val() {
+    let mut futex: i32 = 123;
+
+    // Only wait if the futex value is 456.
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            &futex as *const i32,
+            libc::FUTEX_WAIT,
+            456,
+            ptr::null::<libc::timespec>(),
+        ), -1);
+        assert_eq!(*libc::__errno_location(), libc::EAGAIN);
+    }
+}
+
+fn wait_timeout() {
+    let start = Instant::now();
+
+    let mut futex: i32 = 123;
+
+    // Wait for 200ms, with nobody waking us up early.
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            &futex as *const i32,
+            libc::FUTEX_WAIT,
+            123,
+            &libc::timespec {
+                tv_sec: 0,
+                tv_nsec: 200_000_000,
+            },
+        ), -1);
+        assert_eq!(*libc::__errno_location(), libc::ETIMEDOUT);
+    }
+
+    assert!((200..500).contains(&start.elapsed().as_millis()));
+}
+
+fn wait_wake() {
+    let start = Instant::now();
+
+    static FUTEX: i32 = 0;
+
+    let t2 = thread::spawn(move || {
+        thread::sleep(Duration::from_millis(200));
+        unsafe {
+            assert_eq!(libc::syscall(
+                libc::SYS_futex,
+                &FUTEX as *const i32,
+                libc::FUTEX_WAKE,
+                10, // Wake up at most 10 threads.
+            ), 1); // Woken up one thread.
+        }
+    });
+
+    unsafe {
+        assert_eq!(libc::syscall(
+            libc::SYS_futex,
+            &FUTEX as *const i32,
+            libc::FUTEX_WAIT,
+            0,
+            ptr::null::<libc::timespec>(),
+        ), 0);
+    }
+
+    assert!((200..500).contains(&start.elapsed().as_millis()));
+}
+
+fn main() {
+    wake_nobody();
+    wake_dangling();
+    wait_wrong_val();
+    wait_timeout();
+    wait_wake();
+}

tests/run-pass/concurrency/linux-futex.stderr

@@ -0,0 +1,2 @@
+warning: thread support is experimental. For example, Miri does not detect data races yet.
+