Stage2: multiple user threads based on uniprocessor, see new added test race_adder and threads.

user/src/bin/threads.rs

@@ -0,0 +1,38 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+extern crate alloc;
+
+use user_lib::{thread_create, waittid, exit};
+use alloc::vec::Vec;
+
+pub fn thread_a() -> ! {
+    for _ in 0..1000 { print!("a"); }
+    exit(1)
+}
+
+pub fn thread_b() -> ! {
+    for _ in 0..1000 { print!("b"); }
+    exit(2) 
+}
+
+pub fn thread_c() -> ! {
+    for _ in 0..1000 { print!("c"); }
+    exit(3)
+}
+
+#[no_mangle]
+pub fn main() -> i32 {
+    let mut v = Vec::new();
+    v.push(thread_create(thread_a as usize));
+    v.push(thread_create(thread_b as usize));
+    v.push(thread_create(thread_c as usize));
+    for tid in v.iter() {
+        let exit_code = waittid(*tid as usize);
+        println!("thread#{} exited with code {}", tid, exit_code);
+    }
+    println!("main thread exited.");
+    0
+}