Added condvar examples.

user/src/bin/barrier_condvar.rs

@@ -0,0 +1,72 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+extern crate alloc;
+
+use user_lib::{thread_create, exit, waittid, mutex_create, mutex_lock, mutex_unlock, condvar_create, condvar_signal, condvar_wait};
+use alloc::vec::Vec;
+use core::cell::UnsafeCell;
+use lazy_static::*;
+
+const THREAD_NUM: usize = 3;
+
+struct Barrier {
+    mutex_id: usize,
+    condvar_id: usize,
+    count: UnsafeCell<usize>,
+}
+
+impl Barrier {
+    pub fn new() -> Self {
+        Self {
+            mutex_id: mutex_create() as usize,
+            condvar_id: condvar_create() as usize,
+            count: UnsafeCell::new(0),
+        }
+    }
+    pub fn block(&self) {
+        mutex_lock(self.mutex_id);
+        let mut count = self.count.get();
+        // SAFETY: Here, the accesses of the count is in the
+        // critical section protected by the mutex.
+        unsafe { *count = *count + 1; } 
+        if unsafe { *count } == THREAD_NUM {
+            condvar_signal(self.condvar_id);
+        } else {
+            condvar_wait(self.condvar_id, self.mutex_id);
+            condvar_signal(self.condvar_id);
+        }
+        mutex_unlock(self.mutex_id);
+    }
+}
+
+unsafe impl Sync for Barrier {}
+
+lazy_static! {
+    static ref BARRIER_AB: Barrier = Barrier::new();
+    static ref BARRIER_BC: Barrier = Barrier::new();
+}
+
+fn thread_fn() {
+    for _ in 0..300 { print!("a"); }
+    BARRIER_AB.block();
+    for _ in 0..300 { print!("b"); }
+    BARRIER_BC.block();
+    for _ in 0..300 { print!("c"); }
+    exit(0)
+}
+
+#[no_mangle]
+pub fn main() -> i32 {
+    let mut v: Vec<isize> = Vec::new();
+    for _ in 0..THREAD_NUM {
+        v.push(thread_create(thread_fn as usize, 0));
+    }
+    for tid in v.into_iter() {
+        waittid(tid as usize);
+    }
+    println!("\nOK!");
+    0
+}