Add MutexSpin and several syscalls.

os/src/syscall/sync.rs

@@ -0,0 +1,40 @@
+use crate::task::current_process;
+use crate::sync::MutexSpin;
+use alloc::sync::Arc;
+
+pub fn sys_mutex_create() -> isize {
+    let process = current_process();
+    let mut process_inner = process.inner_exclusive_access();
+    if let Some(id) = process_inner
+        .mutex_list
+        .iter()
+        .enumerate()
+        .find(|(_, item)| item.is_none())
+        .map(|(id, _)| id) {
+        process_inner.mutex_list[id] = Some(Arc::new(MutexSpin::new())); 
+        id as isize
+    } else {
+        process_inner.mutex_list.push(Some(Arc::new(MutexSpin::new())));
+        process_inner.mutex_list.len() as isize - 1
+    }
+}
+
+pub fn sys_mutex_lock(mutex_id: usize) -> isize {
+    let process = current_process();
+    let process_inner = process.inner_exclusive_access();
+    let mutex = Arc::clone(process_inner.mutex_list[mutex_id].as_ref().unwrap());
+    drop(process_inner);
+    drop(process);
+    mutex.lock();
+    0
+}
+
+pub fn sys_mutex_unlock(mutex_id: usize) -> isize {
+    let process = current_process();
+    let process_inner = process.inner_exclusive_access();
+    let mutex = Arc::clone(process_inner.mutex_list[mutex_id].as_ref().unwrap());
+    drop(process_inner);
+    drop(process);
+    mutex.unlock();
+    0
+}