add test_sched.rs with sched_affinity test

test/test.rs

@@ -118,6 +118,7 @@ mod test_net;
 mod test_nix_path;
 mod test_poll;
 mod test_pty;
+mod test_sched;
 #[cfg(any(target_os = "android",
           target_os = "freebsd",
           target_os = "ios",

test/test_sched.rs

@@ -0,0 +1,36 @@
+
+#[cfg(any(target_os = "android",
+          target_os = "linux"))]
+#[test]
+fn test_sched_affinity() {
+    use nix::sched::{sched_getaffinity, sched_setaffinity, CpuSet};
+    use nix::unistd::Pid;
+    use std::mem;
+
+    // If pid is zero, then the mask of the calling process is returned.
+    let initial_affinity = sched_getaffinity(Pid::from_raw(0)).unwrap();
+    let mut at_least_one_cpu = false;
+    let mut last_valid_cpu = 0;
+    for field in 0..(8 * mem::size_of::<libc::cpu_set_t>()) {
+        if initial_affinity.is_set(field).unwrap() {
+            at_least_one_cpu = true;
+            last_valid_cpu = field;
+        }
+    }
+    assert!(at_least_one_cpu);
+
+    // Now restrict the running CPU
+    let mut new_affinity = CpuSet::new();
+    new_affinity.set(last_valid_cpu).unwrap();
+    sched_setaffinity(Pid::from_raw(0), &new_affinity).unwrap();
+
+    // And now re-check the affinity which should be only the one we set.
+    let updated_affinity = sched_getaffinity(Pid::from_raw(0)).unwrap();
+    for field in 0..(8 * mem::size_of::<libc::cpu_set_t>()) {
+        // Should be set only for the CPU we set previously
+        assert_eq!(updated_affinity.is_set(field).unwrap(), field==last_valid_cpu)
+    }
+
+    // Finally, reset the initial CPU set
+    sched_setaffinity(Pid::from_raw(0), &initial_affinity).unwrap();
+}