From 9b65abcfa8c5d7aeac6954b5afa1d9c90fb225d7 Mon Sep 17 00:00:00 2001
From: Yifan Wu <shinbokuow@163.com>
Date: Tue, 16 Feb 2021 20:50:24 +0800
Subject: [PATCH] Fix lock uses in ch5

---
 os/src/task/mod.rs       | 14 +++++++-------
 os/src/task/processor.rs |  8 +++++---
 os/src/task/task.rs      | 16 ++++------------
 3 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/os/src/task/mod.rs b/os/src/task/mod.rs
index 31bc435a..e943016c 100644
--- a/os/src/task/mod.rs
+++ b/os/src/task/mod.rs
@@ -28,14 +28,13 @@ pub fn suspend_current_and_run_next() {
     // There must be an application running.
     let task = take_current_task().unwrap();
 
-    // ---- temporarily hold current PCB lock
-    let task_cx_ptr2 = task.acquire_inner_lock().get_task_cx_ptr2();
-    // ---- release current PCB lock
-
-    // ++++ temporarily hold current PCB lock
+    // ---- hold current PCB lock
+    let mut task_inner = task.acquire_inner_lock();
+    let task_cx_ptr2 = task_inner.get_task_cx_ptr2();
     // Change status to Ready
-    task.acquire_inner_lock().task_status = TaskStatus::Ready;
-    // ++++ release current PCB lock
+    task_inner.task_status = TaskStatus::Ready;
+    drop(task_inner);
+    // ---- release current PCB lock
 
     // push back to ready queue.
     add_task(task);
@@ -58,6 +57,7 @@ pub fn exit_current_and_run_next(exit_code: i32) {
     {
         let mut initproc_inner = INITPROC.acquire_inner_lock();
         for child in inner.children.iter() {
+            child.acquire_inner_lock().parent = Some(Arc::downgrade(&INITPROC));
             initproc_inner.children.push(child.clone());
         }
     }
diff --git a/os/src/task/processor.rs b/os/src/task/processor.rs
index a1c753f0..e6895c40 100644
--- a/os/src/task/processor.rs
+++ b/os/src/task/processor.rs
@@ -35,8 +35,10 @@ impl Processor {
             if let Some(task) = fetch_task() {
                 let idle_task_cx_ptr2 = self.get_idle_task_cx_ptr2();
                 // acquire
-                let next_task_cx_ptr2 = task.acquire_inner_lock().get_task_cx_ptr2();
-                task.acquire_inner_lock().task_status = TaskStatus::Running;
+                let mut task_inner = task.acquire_inner_lock();
+                let next_task_cx_ptr2 = task_inner.get_task_cx_ptr2();
+                task_inner.task_status = TaskStatus::Running;
+                drop(task_inner);
                 // release
                 self.inner.borrow_mut().current = Some(task);
                 unsafe {
@@ -52,7 +54,7 @@ impl Processor {
         self.inner.borrow_mut().current.take()
     }
     pub fn current(&self) -> Option<Arc<TaskControlBlock>> {
-        self.inner.borrow().current.as_ref().map(|task| task.clone())
+        self.inner.borrow().current.as_ref().map(|task| Arc::clone(task))
     }
 }
 
diff --git a/os/src/task/task.rs b/os/src/task/task.rs
index e58c8ae8..1c733da1 100644
--- a/os/src/task/task.rs
+++ b/os/src/task/task.rs
@@ -67,7 +67,6 @@ impl TaskControlBlock {
             .translate(VirtAddr::from(TRAP_CONTEXT).into())
             .unwrap()
             .ppn();
-        let task_status = TaskStatus::Ready;
         // alloc a pid and a kernel stack in kernel space
         let pid_handle = pid_alloc();
         let kernel_stack = KernelStack::new(&pid_handle);
@@ -81,7 +80,7 @@ impl TaskControlBlock {
                 trap_cx_ppn,
                 base_size: user_sp,
                 task_cx_ptr: task_cx_ptr as usize,
-                task_status,
+                task_status: TaskStatus::Ready,
                 memory_set,
                 parent: None,
                 children: Vec::new(),
@@ -97,9 +96,7 @@ impl TaskControlBlock {
             }),
         };
         // prepare TrapContext in user space
-        // ---- acquire child PCB lock
         let trap_cx = task_control_block.acquire_inner_lock().get_trap_cx();
-        // ---- release child PCB lock
         *trap_cx = TrapContext::app_init_context(
             entry_point,
             user_sp,
@@ -123,13 +120,8 @@ impl TaskControlBlock {
         inner.memory_set = memory_set;
         // update trap_cx ppn
         inner.trap_cx_ppn = trap_cx_ppn;
-        drop(inner);
-        // **** release current PCB lock manually
-
         // initialize trap_cx
-        // **** acquire current PCB lock
-        let trap_cx = self.acquire_inner_lock().get_trap_cx();
-        // **** release current PCB lock
+        let trap_cx = inner.get_trap_cx();
         *trap_cx = TrapContext::app_init_context(
             entry_point,
             user_sp,
@@ -137,6 +129,7 @@ impl TaskControlBlock {
             self.kernel_stack.get_top(),
             trap_handler as usize,
         );
+        // **** release current PCB lock
     }
     pub fn fork(self: &Arc<TaskControlBlock>) -> Arc<TaskControlBlock> {
         // ---- hold parent PCB lock
@@ -149,7 +142,6 @@ impl TaskControlBlock {
             .translate(VirtAddr::from(TRAP_CONTEXT).into())
             .unwrap()
             .ppn();
-        let task_status = TaskStatus::Ready;
         // alloc a pid and a kernel stack in kernel space
         let pid_handle = pid_alloc();
         let kernel_stack = KernelStack::new(&pid_handle);
@@ -172,7 +164,7 @@ impl TaskControlBlock {
                 trap_cx_ppn,
                 base_size: parent_inner.base_size,
                 task_cx_ptr: task_cx_ptr as usize,
-                task_status,
+                task_status: TaskStatus::Ready,
                 memory_set,
                 parent: Some(Arc::downgrade(self)),
                 children: Vec::new(),